Samacheer Kalvi Class 10 Science Solutions Chapter 12 Plant Anatomy and Plant Physiology

Samacheer Kalvi 10th Science Plant Anatomy and Plant Physiology Text Book Back Questions and Answers

I. Choose the correct answer:

 

Question 1. Casparian strips are present in the root.
(a) cortex
(b) pith
(c) pericycle
(d) endodermis
Answer: (d) endodermis
In simple words: Casparian strips are like waterproof belts found in the endodermis layer of a plant's root. They make sure water and nutrients enter the plant cells in a controlled way.

🎯 Exam Tip: Remember that Casparian strips are a key feature of the endodermis in roots, playing a vital role in regulating water and nutrient flow into the vascular cylinder.

 

Question 2. The endarch condition is the characteristic feature of _____
(a) root
(b) stem
(c) leaves
(d) flower.
Answer: (b) stem
In simple words: Endarch means that the smaller xylem cells are found towards the center, while larger ones are towards the outside. This pattern is usually seen in plant stems.

🎯 Exam Tip: Understand that endarch xylem, where protoxylem is internal, is typical for stems, while exarch xylem, with protoxylem external, is found in roots.

 

Question 3. The xylem and phloem arranged side by side on same radius is called:
(a) radial
(b) amphivasal
(c) conjoint
(d) None of these
Answer: (c) conjoint
In simple words: If xylem and phloem are lined up next to each other on the same line in a plant part, it's called a conjoint arrangement.

🎯 Exam Tip: Differentiate between radial (xylem and phloem on different radii, like in roots) and conjoint (xylem and phloem on the same radius, common in stems) vascular bundles.

 

Question 4. Which is formed during anaerobic respiration:
(b) Ethyl alcohol
(c) Acetyl CoA
(d) Pyruvate
Answer: (b) Ethyl alcohol
In simple words: When there is no oxygen, some living things make ethyl alcohol during breathing. This process is also called alcoholic fermentation.

🎯 Exam Tip: Remember that anaerobic respiration has different end products depending on the organism; in yeast, it's ethyl alcohol, while in muscle cells, it's lactic acid.

 

Question 5. Kreb's cycle takes place in _____
(a) chloroplast
(b) mitochondrial matrix
(c) stomata
(d) inner mitochondrial membrane.
Answer: (b) mitochondrial matrix
In simple words: The Kreb's cycle, a major step in getting energy from food, happens in the main fluid-filled part of the mitochondria.

🎯 Exam Tip: Associate the mitochondrial matrix with the Krebs cycle and the inner mitochondrial membrane with the electron transport chain, as these are distinct locations for specific respiratory processes.

 

Question 6. Oxygen is produced at what point during photosynthesis?
(a) when ATP is converted to ADP
(b) when CO2 is fixed
(c) when H2O is splitted
(d) All of these
Answer: (c) when H2O is splitted
In simple words: Oxygen is made during photosynthesis when water molecules break apart. It is released as a byproduct of this crucial step.

🎯 Exam Tip: Remember that water splitting (photolysis) during the light-dependent reactions is the direct source of all oxygen released by plants during photosynthesis.

 

II. Fill in the blanks:

 

Question 1. Cortex lies between ..........
Answer: epidermis and Pericycle
In simple words: The cortex is found between the outer skin (epidermis) and an inner layer called the pericycle in plants.

🎯 Exam Tip: Visualizing a cross-section of a root or stem helps to understand the relative positions of layers like the epidermis, cortex, and stele.

 

Question 2. Xylem and phloem occur on the same radius constitute a vascular bundle called ..........
Answer: conjoint bundles
In simple words: If xylem and phloem are next to each other on the same line, they make a conjoint vascular bundle.

🎯 Exam Tip: Recall that "conjoint" describes vascular bundles where xylem and phloem share a radius, while "radial" describes them on different radii.

 

Question 3. Glycolysis takes place in ..........
Answer: cytoplasm
In simple words: Glycolysis, the first step in breaking down sugar for energy, happens in the cytoplasm, the main fluid part of a cell.

🎯 Exam Tip: Remember that glycolysis is an anaerobic process, meaning it occurs without oxygen, and happens in the cytoplasm, unlike the later stages of respiration.

 

Question 4. __________ is the splitting of water molecules during photosynthesis.
Answer: splitting of Water molecules
In simple words: In photosynthesis, water molecules are split apart. This action helps make energy and also releases oxygen.

🎯 Exam Tip: Connecting the splitting of water molecules to the release of oxygen and the provision of electrons is key to understanding the light-dependent reactions.

 

Question 5. ........ is the ATP factory of the cells.
Answer: Mitochondria
In simple words: Mitochondria are like the energy factories of cells because they make ATP, which is the cell's power.

🎯 Exam Tip: Always remember mitochondria's role in ATP production, highlighting its importance for almost all cellular activities.

 

III. State whether the statements are true or false. Correct the false statement.

 

Question 1. Phloem tissue is involved in the transport of water in plants.
Answer: False. Phloem tissue's primary role in plants is to transport sugars (food) from leaves to other parts of the plant where it is needed for growth or storage. Water transport is mainly the function of xylem tissue.
In simple words: False. Phloem carries food, like sugar, around the plant, not water.

🎯 Exam Tip: Clearly distinguish between xylem (water transport) and phloem (food transport) functions; this is a common point of confusion.

 

Question 2. The waxy protective covering of a plant is called as the cuticle.
Answer: True. The cuticle is a waxy layer found on the outer surface of plant leaves and stems. Its main job is to reduce water loss through evaporation.
In simple words: True. The waxy outer layer on plants, which helps them save water, is called the cuticle.

🎯 Exam Tip: Understand that the cuticle is a key adaptation for terrestrial plants, preventing excessive water loss and protecting against pathogens.

 

Question 3. In monocot, stem cambium is present in between xylem and phloem.
Answer: False. In monocot stems, cambium tissue is typically absent between the xylem and phloem bundles. This means that monocot stems generally do not undergo secondary growth, which is the increase in girth.
In simple words: False. Monocot stems do not have cambium between their xylem and phloem, so they cannot grow wider like dicots.

🎯 Exam Tip: Differentiate monocots from dicots by the presence (dicots) or absence (monocots) of cambium, which is responsible for secondary growth.

 

Question 4. Palisade parenchyma cells occur below the upper epidermis in the dicot root.
Answer: False. Palisade parenchyma cells, which are rich in chloroplasts for photosynthesis, are found just beneath the upper epidermis in dicot leaves. They are not present in dicot roots, as roots do not perform photosynthesis.
In simple words: False. Palisade cells are in dicot leaves, under the top skin, for making food. They are not in roots.

🎯 Exam Tip: Remember that palisade parenchyma is a specialized tissue for photosynthesis, found in leaves, which are adapted for light absorption.

 

Question 5. Mesophyll contains chlorophyll.
Answer: True. Mesophyll is the inner tissue of a leaf, and its cells are rich in chlorophyll. Chlorophyll is the green pigment essential for capturing sunlight during photosynthesis.
In simple words: True. The inner part of a leaf, called mesophyll, has chlorophyll. This is the green stuff that helps plants make food from sunlight.

🎯 Exam Tip: Understand that the mesophyll is the primary site of photosynthesis in leaves due to its abundance of chlorophyll-containing cells.

 

Question 6. Anaerobic respiration produces more ATP than aerobic respiration.
Answer: False. Aerobic respiration, which requires oxygen, is much more efficient at producing ATP (energy) than anaerobic respiration. Aerobic respiration can generate around 30-32 ATP molecules per glucose, while anaerobic respiration typically produces only 2 ATP molecules.
In simple words: False. Aerobic breathing makes much more energy (ATP) than anaerobic breathing. Aerobic uses oxygen, anaerobic does not.

🎯 Exam Tip: A key difference between aerobic and anaerobic respiration is the amount of ATP produced, with aerobic respiration being far more energy-efficient.

 

IV. Match the following:

 

Question 1. Match the following.

Answer:
A. (iii) Amphicribal: This type of vascular bundle has phloem surrounded by xylem, a characteristic found in ferns.
B. (iv) Cambium: This tissue is responsible for secondary growth, which increases the girth of stems and roots.
C. (i) Amphivasal: In this bundle, xylem is surrounded by phloem, as seen in plants like Dracaena.
D. (v) Xylem: The primary function of xylem is the conduction of water and minerals from the roots to the rest of the plant.
E. (ii) Phloem: Phloem is responsible for the translocation of food, mainly sugars, from leaves to other parts of the plant.
In simple words: Amphicribal bundles are in ferns, cambium helps plants grow thicker, amphivasal bundles are in Dracaena, xylem carries water, and phloem carries food.

🎯 Exam Tip: For matching questions, remember the key functions and structures of plant tissues, especially their roles in transport and growth, to correctly pair them.

 

V. Answer in a sentence:

 

Question 1. What is the collateral vascular bundle?
Answer: A collateral vascular bundle is formed when both xylem and phloem tissues are located on the same radius within a vascular bundle, and the phloem is positioned towards the outer side, away from the center. This arrangement is very common in plant stems.
In simple words: A collateral vascular bundle is when xylem and phloem are on the same line, with the phloem on the outside.

🎯 Exam Tip: Visualizing the arrangement of xylem and phloem within a vascular bundle helps distinguish between different types like collateral and radial.

 

Question 2. Where does the carbon that is used in photosynthesis come from?
Answer: The carbon required for photosynthesis by plants is obtained from carbon dioxide (\( \text{CO}_2 \)) present in the atmosphere, which enters the plant through small pores called stomata. Plants absorb this atmospheric carbon dioxide to produce sugars.
In simple words: The carbon for photosynthesis comes from the carbon dioxide gas in the air around us.

🎯 Exam Tip: Emphasize that plants use carbon dioxide from the atmosphere, not from the soil, for building their organic molecules.

 

Question 3. What is the common step in aerobic and anaerobic pathway?
Answer: Glycolysis is the initial metabolic pathway that is shared between both aerobic and anaerobic respiration. In this step, glucose is broken down into pyruvic acid, and it occurs in the cytoplasm without the need for oxygen. This fundamental process starts the energy extraction from glucose.
In simple words: The first step that is the same for both breathing with oxygen (aerobic) and breathing without oxygen (anaerobic) is called glycolysis.

🎯 Exam Tip: Remember that glycolysis is the universal first stage of glucose breakdown for energy, occurring in nearly all organisms, regardless of oxygen availability.

 

VI. Short answer questions:

 

Question 1. Give an account on vascular bundle of dicot stem.
Answer: Vascular bundles in a dicot stem have a specific structure. They are **conjoint**, meaning xylem and phloem are on the same radius. They are **collateral**, with phloem located towards the periphery and xylem towards the center. They show an **endarch** arrangement, where the protoxylem (the first-formed, smaller xylem elements) is towards the center and metaxylem (later-formed, larger xylem elements) is towards the periphery. Importantly, they are **open** because cambium tissue is present between the xylem and phloem, allowing for secondary growth. These bundles are typically arranged in a ring shape around the pith. This organized arrangement contributes to the stem's structural strength and efficient transport.
In simple words: Dicot stems have vascular bundles where xylem and phloem are together on the same line, with the food-carrying phloem on the outside. They are "open" because they have a cambium layer that helps them grow wider, and they form a ring inside the stem.

🎯 Exam Tip: Use the terms 'conjoint', 'collateral', 'endarch', and 'open' to accurately describe the vascular bundles of a dicot stem, as these are key distinguishing features.

 

Question 2. Write a short note on mesophyll.
Answer: Mesophyll is the specialized tissue found between the upper and lower epidermis of a dicot leaf. It is primarily responsible for photosynthesis and is divided into two distinct types: 1. **Palisade Parenchyma:** These cells are long and column-shaped, located just below the upper epidermis. They contain many chloroplasts and are the main site for photosynthesis. These cells are tightly packed, with few or no air spaces. 2. **Spongy Parenchyma:** Found below the palisade layer, these cells are irregularly shaped and have large air spaces between them. They contain fewer chloroplasts than palisade cells and are important for gas exchange within the leaf. In monocot leaves, the mesophyll is not differentiated into these two distinct layers. This differentiation helps maximize light absorption and gas exchange for efficient photosynthesis.
In simple words: Mesophyll is the middle tissue in a dicot leaf, found between the top and bottom skin layers. It has two parts: palisade cells (long, for making food) and spongy cells (irregular, with air gaps for gas exchange).

🎯 Exam Tip: When describing mesophyll, always mention its two types in dicot leaves (palisade and spongy parenchyma) and their respective functions and structures.

 

Question 3. Draw and label the structure of oxysomes.
Answer: Oxysomes are small, stalked particles found on the inner mitochondrial membrane. They are also known as \( \text{F}_0\text{-F}_1 \) particles or elementary particles. These structures contain enzymes crucial for ATP synthesis, acting as the site where ADP is converted into ATP during oxidative phosphorylation. (A diagram of the oxysome structure, showing its F1 head and stalk, would typically illustrate this.)
In simple words: Oxysomes are tiny, mushroom-shaped parts on the inner wall of mitochondria. They help make ATP, which is the energy currency of the cell.

🎯 Exam Tip: Remember that oxysomes are vital for ATP production within mitochondria and are key components of the electron transport chain.

 

Question 4. Name the three basic – tissues systems in flowering plants.
Answer: Flowering plants are organized into three fundamental tissue systems, each performing specialized roles: * **Dermal or Epidermal Tissue System:** This system forms the outer protective covering of the plant, like its "skin." It includes the epidermis, which protects against water loss and pathogens. * **Ground Tissue System:** This system makes up the bulk of the plant body, filling the spaces between the dermal and vascular tissues. It's involved in photosynthesis, storage, and support. * **Vascular Tissue System:** This system is responsible for long-distance transport within the plant. It consists of xylem (for water transport) and phloem (for food transport). These three systems work together to ensure the plant's survival and growth.
In simple words: Flowering plants have three main tissue systems: the outer skin (dermal), the main body tissue (ground), and the tubes that carry water and food (vascular).

🎯 Exam Tip: Learning the three basic tissue systems and their primary functions is foundational to understanding plant anatomy.

 

Question 5. What is photosynthesis and where in a cell does it occur?
Answer: Photosynthesis is a vital biological process where autotrophic organisms, such as green plants, algae, and some bacteria, convert light energy from the sun into chemical energy (food). This process uses carbon dioxide and water to produce glucose and oxygen. In eukaryotic cells (like plant cells), photosynthesis mainly occurs in the chloroplasts, which are specialized organelles containing chlorophyll. Chloroplasts are like tiny food factories inside plant cells.
In simple words: Photosynthesis is how green plants and other organisms make their own food using sunlight, water, and air. This happens inside the chloroplasts within their cells.

🎯 Exam Tip: Define photosynthesis as light energy conversion into chemical energy, and always specify chloroplasts as the site of this process in plant cells.

 

Question 6. What is respiratory quotient?
Answer: The Respiratory Quotient (RQ) is a scientific measurement that shows the ratio of the volume of carbon dioxide (\( \text{CO}_2 \)) released to the volume of oxygen (\( \text{O}_2 \)) consumed during respiration. This ratio is typically expressed using the formula:
\[ \text{RQ} = \frac { \text{Volume of CO}_2 \text{ liberated} }{ \text{Volume of O}_2 \text{ consumed} } \] The RQ value can vary depending on the type of respiratory substrate (e.g., carbohydrates, fats, proteins) being broken down for energy.
In simple words: Respiratory Quotient (RQ) is a number that tells us how much carbon dioxide is let out compared to how much oxygen is taken in during breathing.

🎯 Exam Tip: Memorize the formula for Respiratory Quotient and understand that its value indicates the type of nutrient being used for respiration.

 

Question 7. Why should the light - dependent reaction occur before the light-independent reaction?
Answer: The light-dependent reactions of photosynthesis must happen before the light-independent reactions (also known as the Calvin cycle or dark reactions) because they produce the necessary energy carriers. In the light-dependent stage, photosynthetic pigments absorb sunlight and convert it into chemical energy, forming ATP (adenosine triphosphate) and NADPH2. These energy-rich molecules then move from the grana to the stroma of the chloroplast. The ATP and NADPH2 are essential for the light-independent reactions, where carbon dioxide (\( \text{CO}_2 \)) is reduced to form carbohydrates (sugars). Without the energy from the light-dependent reactions, the light-independent reactions cannot proceed.
In simple words: Light-dependent reactions happen first because they make the energy (ATP and NADPH2) needed for the light-independent reactions to build sugars from carbon dioxide.

🎯 Exam Tip: Understand that ATP and NADPH2 are the crucial links between the light-dependent and light-independent stages of photosynthesis, transferring energy from light to sugar synthesis.

 

Question 8. Write the reaction for photosynthesis.
Answer: The overall chemical reaction that summarizes the process of photosynthesis is:
\[ \text{6CO}_2 + \text{12 H}_2\text{O} \xrightarrow{\text{Light}}_{\text{Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + \text{6H}_2\text{O} + \text{6O}_2 \uparrow \] In this reaction, six molecules of carbon dioxide and twelve molecules of water, in the presence of light and chlorophyll, are converted into one molecule of glucose (a sugar), six molecules of water, and six molecules of oxygen. This equation shows how plants convert simple inorganic substances into complex organic food.
In simple words: Photosynthesis turns carbon dioxide and water into sugar and oxygen, using sunlight and chlorophyll.

🎯 Exam Tip: Memorize the balanced chemical equation for photosynthesis, including the reactants, products, and the conditions (light, chlorophyll).

 

VII. Long Answer Questions:

 

Question 1. Differentiate the following: (a) Monocot root and Dicot root
Answer: Here are the key differences between monocot and dicot roots:

Monocot roots often have a more fibrous root system, while dicot roots usually have a taproot system.
In simple words: Monocot roots have many xylem bundles and a big center (pith), with no secondary growth. Dicot roots have fewer xylem bundles, a small or no center, and can grow wider.

🎯 Exam Tip: Focus on the number of xylem bundles, the presence/absence of pith, and the capacity for secondary growth as key differentiators for monocot and dicot roots.

 

Question 1. (b) Aerobic and Anaerobic respiration
Answer: Here's a comparison between aerobic and anaerobic respiration:

Both processes begin with glycolysis, but their subsequent pathways and energy yields differ significantly.
In simple words: Aerobic breathing uses oxygen, completely breaks down sugar, and makes a lot of energy, giving off carbon dioxide and water. Anaerobic breathing does not use oxygen, partly breaks down sugar, makes little energy, and gives off alcohol or lactic acid, plus carbon dioxide.

🎯 Exam Tip: When comparing aerobic and anaerobic respiration, clearly state the oxygen requirement, the extent of glucose breakdown, the final products, and the energy yield.

 

Question 2. Describe and name three stages of cellular respiration that aerobic organisms use to obtain energy from glucose.
Answer: Aerobic organisms obtain energy from glucose through three main stages of cellular respiration: 1. **Glycolysis (Glucose Splitting):** This is the first step, occurring in the cytoplasm. In glycolysis, one molecule of glucose (a 6-carbon sugar) is broken down into two molecules of pyruvic acid (a 3-carbon compound). This initial stage produces a small amount of ATP and NADH. 2. **Krebs Cycle (Citric Acid Cycle):** Following glycolysis, the pyruvic acid molecules enter the mitochondrial matrix. Here, they are further oxidized through a series of reactions known as the Krebs cycle. This cycle produces more ATP, as well as electron carriers like NADH and \( \text{FADH}_2 \), and releases carbon dioxide (\( \text{CO}_2 \)). 3. **Electron Transport Chain (ETC):** This final and most energy-efficient stage takes place on the inner membrane of the mitochondria. The NADH and \( \text{FADH}_2 \) molecules produced in the earlier stages donate electrons to the ETC. As these electrons move along the chain, they release energy, which is used to synthesize a large amount of ATP through a process called oxidative phosphorylation. Oxygen acts as the final electron acceptor at the end of the chain, forming water. This entire sequence efficiently extracts maximum energy from glucose.
In simple words: Aerobic organisms get energy from sugar in three steps: 1. Sugar is split into smaller parts (glycolysis). 2. These parts are broken down more in mitochondria, making energy carriers (Krebs cycle). 3. The energy carriers release a lot of energy to make ATP (electron transport chain).

🎯 Exam Tip: Clearly define the location and main outputs (ATP, electron carriers, waste products) for each of the three stages of aerobic respiration: Glycolysis, Krebs Cycle, and Electron Transport Chain.

 

Question 3. How does the light dependent reaction differ from the light independent reaction? What are the end product and reactants in each? Where does each reaction occur
Answer: The light-dependent and light-independent reactions are two distinct but interconnected stages of photosynthesis:

The products of the light-dependent reactions (ATP and NADPH2) are directly used as energy and reducing power for the light-independent reactions, demonstrating their close interdependence.
In simple words: Light-dependent reactions use sunlight, water, and pigments to make energy (ATP, NADPH2) and oxygen in the thylakoids. Light-independent reactions use that energy, plus carbon dioxide, to make sugars in the stroma.

🎯 Exam Tip: Highlight the unique reactants, products, and locations for each phase, and explain how the energy carriers (ATP and NADPH2) link the two reactions.

 

VIII. Higher Order Thinking Skills(HOTS):

 

Question 1. The reactions of photosynthesis make up a biochemical pathway. (a) What are the reactants and products for both light and dark reactions.
Answer: Photosynthesis occurs in two main stages: * **Light-Dependent Reactions:** * **Reactants:** Light energy, water (\( \text{H}_2\text{O} \)), ADP (adenosine diphosphate), and \( \text{NADP}^+ \) (nicotinamide adenine dinucleotide phosphate). * **Products:** ATP (adenosine triphosphate), NADPH (reduced nicotinamide adenine dinucleotide phosphate), and oxygen (\( \text{O}_2 \)). * **Light-Independent Reactions (Calvin Cycle / Dark Reactions):** * **Reactants:** Carbon dioxide (\( \text{CO}_2 \)), ATP, and NADPH. * **Products:** Glucose (or other carbohydrates), ADP, and \( \text{NADP}^+ \). These two sets of reactions are interdependent, with the products of the light reactions fueling the dark reactions.
In simple words: For light reactions, plants use sunlight and water to make energy (ATP, NADPH) and oxygen. For dark reactions, they use carbon dioxide and the energy from light reactions to make sugar.

🎯 Exam Tip: Clearly listing reactants and products for each phase (light and dark) is essential for full marks, showing an understanding of their distinct roles.

 

Question 1. (b) Explain how the biochemical pathway of photosynthesis recycles many of its own reactions and identify the recycled reactants.
Answer: The biochemical pathway of photosynthesis effectively recycles several key molecules between its light-dependent and light-independent reactions. The light reactions utilize light energy to produce ATP and NADPH2. These energy carriers are then used in the Calvin cycle (light-independent reactions) to fix carbon dioxide and produce sugars. After releasing their energy and electrons in the Calvin cycle, ATP is converted back to ADP and inorganic phosphate (\( \text{Pi} \)), and NADPH2 is converted back to \( \text{NADP}^+ \). These de-energized forms (ADP, \( \text{Pi} \), and \( \text{NADP}^+ \)) are then recycled back to the thylakoid membranes for the light-dependent reactions to be re-energized by sunlight, continuing the cycle. This recycling ensures that the plant can continuously produce sugars as long as light and \( \text{CO}_2 \) are available. **Recycled Reactants:** The key reactants that are recycled are ADP (recycled to ATP), \( \text{NADP}^+ \) (recycled to NADPH2), and inorganic phosphate (\( \text{Pi} \)).
In simple words: Photosynthesis reuses its parts like a loop. The light reactions make energy molecules (ATP and NADPH2). The dark reactions use these to make sugar, then send back the empty energy molecules (ADP and \( \text{NADP}^+ \)) to the light reactions to be filled up with energy again.

🎯 Exam Tip: Emphasize the cyclical nature of ATP/ADP and NADPH/NADP+ exchange between the two photosynthetic stages as crucial for continuous sugar production.

 

Question 2. Where do the light-dependent reaction and the Calvin cycle occur in the chloroplast?
Answer: Within the chloroplast, the light-dependent reactions and the Calvin cycle (light-independent reactions) occur in distinct locations: * The **light-dependent reactions** take place on the **thylakoid membranes**. These membranes are stacked into structures called grana, which provide a large surface area for light absorption and energy conversion. * The **Calvin cycle** (light-independent reactions) occurs in the **stroma**, which is the fluid-filled space surrounding the thylakoids within the chloroplast. This separation allows for specialized conditions for each stage of photosynthesis.
In simple words: Light-dependent reactions happen on the thylakoid membranes (in grana) inside the chloroplast. The Calvin cycle (light-independent reactions) happens in the stroma, which is the fluid part of the chloroplast.

🎯 Exam Tip: Accurately identifying the thylakoids for light reactions and the stroma for the Calvin cycle is fundamental to understanding chloroplast function.

 

Samacheer Kalvi 10th Science Plant Anatomy and Plant Physiology Additional Important Questions and Answers

I. Choose the correct answer:

 

Question 1. The root hairs originate from:
(a) trichoblast
(b) endodermis
(c) hypodermis
(d) pericycle
Answer: (a) trichoblast
In simple words: Root hairs grow from special cells in the root's outer layer called trichoblasts. They help the root soak up water and nutrients.

🎯 Exam Tip: Understand that root hairs are extensions of epidermal cells, not a separate layer, and their primary function is absorption, which is directly aided by their origin from trichoblasts.

 

Question 2. Sachs classified tissue system in plants into _____
(a) five types
(b) two types
(c) three types
(d) four types.
Answer: (c) three types
In simple words: Sachs sorted plant tissues into three main types: the outer skin (dermal), the main body tissue (ground), and the transport tubes (vascular).

🎯 Exam Tip: Recall Sachs' classification of plant tissues into dermal, ground, and vascular systems, as this is a fundamental concept in plant anatomy.

 

Question 3. The innermost layer of the cortex is:
(a) epidermis
(b) hypodermis
(c) endodermis
(d) pericycle
Answer: (c) endodermis
In simple words: The endodermis is the layer found furthest inside the cortex. It acts like a border before the plant's central transport system.

🎯 Exam Tip: Remember the endodermis as the key regulating layer at the inner boundary of the cortex, particularly important in roots for selective absorption.

 

Question 4. The powerhouse of the cell or ATP factory of the cells _____
(a) Plastids
(b) Vacuoles
(c) Nucleus
(d) Mitochondria.
Answer: (d) Mitochondria.
In simple words: Mitochondria are called the cell's powerhouse because they make most of the energy, called ATP, that the cell needs to work.

🎯 Exam Tip: Always associate mitochondria with energy production (ATP synthesis) through cellular respiration.

 

Question 5. The vascular bundle with protoxylem facing centre of the stem is:
(a) exarch
(b) endarch
(c) tetrarch
(d) polyarch
Answer: (b) endarch
In simple words: In an endarch vascular bundle, the smallest xylem part faces the middle of the stem.

🎯 Exam Tip: Distinguish endarch (protoxylem inward, typical of stems) from exarch (protoxylem outward, typical of roots) based on the orientation of protoxylem and metaxylem.

 

Question 6. This is the first step of both Aerobic and Anaerobic respiration _____
(a) Electron transport chain
(b) Respiratory Quotient
(c) Glycolysis
(d) Kreb's Cycle.
Answer: (c) Glycolysis
In simple words: Glycolysis is the very first step in breaking down sugar for energy, whether a cell uses oxygen or not.

🎯 Exam Tip: Remember that glycolysis is universal across almost all forms of life and is the starting point for all glucose metabolism pathways for energy production.

 

Question 7. The vascular bundle in the leaf is:
(a) collateral and open
(b) collateral and closed
(c) bicollateral and open
(d) collateral and exarch
Answer: (b) collateral and closed
In simple words: Leaf vascular bundles have xylem and phloem next to each other (collateral) and do not have cambium, so they can't grow thicker (closed).

🎯 Exam Tip: Understand that most leaves have closed vascular bundles because they do not undergo secondary growth, unlike many stems which have open bundles.

 

Question 8. Photosynthesis takes place in:
(a) mitochondria
(b) peroxisomes
(c) chloroplast
(d) ribosomes
Answer: (c) chloroplast
In simple words: Photosynthesis happens only in the chloroplasts, which are the green parts inside plant cells.

🎯 Exam Tip: Always associate chloroplasts as the primary site for photosynthesis in plant cells, similar to how mitochondria are the sites for respiration.

 

Question 9. The dark reaction of photosynthesis were discovered by:
(a) Embden and Meyer
(b) Melvin and Calvin
(c) Kreb
(d) Pamas
Answer: (b) Melvin and Calvin
In simple words: The dark reactions of photosynthesis, which make sugar, were found by scientists named Melvin and Calvin.

🎯 Exam Tip: Remember Melvin Calvin's contribution to understanding the light-independent reactions (Calvin cycle) and carbon fixation.

 

Question 10. __________ is the organelle of cell respiration.
(a) mitochondria
(b) chloroplast
(d) cell wall
Answer: (a) mitochondria
In simple words: Mitochondria are the cell parts where breathing happens to make energy.

🎯 Exam Tip: Clearly distinguish the functions of mitochondria (respiration) from chloroplasts (photosynthesis) within eukaryotic cells.

 

Question 11. The hypodermis of monocot stem consists of:
(a) Collenchyma
(b) Sclsrenchyma
(c) Angular collenchyma
(d) Parenchyma
Answer: (b) Sclsrenchyma
In simple words: The hypodermis in a monocot stem is made up of sclerenchyma cells, which are tough and provide support. It's like the strong outer layer beneath the skin of the stem.

🎯 Exam Tip: Remember that monocot stems have a sclerenchymatous hypodermis, while dicot stems typically have a collenchymatous hypodermis, a key difference for identification.

 

Question 12. The layer that is morphologically similar to the endodermis found in the root is:
(a) periderm
(b) epidermis
(c) starch sheath
(d) mesophyll tissue
Answer: (c) starch sheath
In simple words: The starch sheath is a layer in stems that is similar in structure and function to the endodermis found in roots. Both layers help control what goes into the inner parts of the plant.

🎯 Exam Tip: Understanding homologous structures helps in comparing plant parts and their functions across different organs like roots and stems.

 

Question 13. Pericycle is absent in:
(a) dicot stem
(b) monocot root
(c) dicot root
(d) monocot stem
Answer: (d) monocot stem
In simple words: The pericycle, which is usually found in roots and some stems, is not present in monocot stems. This is one of the key differences in their internal structure.

🎯 Exam Tip: Knowledge of the presence or absence of specific tissues like the pericycle is crucial for distinguishing between monocot and dicot structures.

 

Question 14. Which of the following is not a characteristic feature of spongy parenchyma?
(a) Gaseous exchange
(b) Photosynthesis
(c) Irregular
(d) Closely arranged
Answer: (d) Closely arranged
In simple words: Spongy parenchyma cells are usually irregularly shaped and have many air spaces, which is opposite to being closely arranged. They are important for gas exchange and photosynthesis.

🎯 Exam Tip: Spongy parenchyma cells have large intercellular spaces that facilitate gas diffusion, a distinct feature compared to palisade parenchyma which is more compact.

 

Question 15. Which of the following is not applicable to a dicot stem?
(a) wedge shaped
(b) endarch
(c) collateral
(d) closed
Answer: (d) closed
In simple words: Dicot stems have open vascular bundles, meaning they contain cambium for secondary growth, unlike closed bundles found in monocots. The other options are typically found in dicot stems.

🎯 Exam Tip: Remember that "open" vascular bundles (with cambium) allow for secondary growth in dicots, while "closed" bundles (without cambium) prevent it in monocots.

II. Application Based Question:

 

Question 1. In the given flow chart showing different layers of a monocot root, what are A and B?
(a) A – Hypodermis, B – Vascular bundle
(b) A – Cortex, B – Vascular bundle
(c) A – Cortex, B – Xylem
Answer: (b) A – Cortex, B – Vascular bundle
In simple words: In the flow of layers in a monocot root, 'A' represents the cortex, which is just inside the epidermis. 'B' represents the vascular bundle, found inside the pith and pericycle.

🎯 Exam Tip: Understanding the correct sequence of tissue layers in roots is fundamental for identifying monocot versus dicot structures and their functions.

 

Question 2. Casparian strips are a characteristic feature of A (endodermis) and are made up of B. What are A and B respectively?
(a) shoot, suberin
(b) root, lignin
(c) root, suberin
(d) root and shoot, suberin
Answer: (c) root, suberin
In simple words: Casparian strips are special bands found in the endodermis of roots. They are made of suberin, a waxy substance, which helps control water movement.

🎯 Exam Tip: Casparian strips play a vital role in the apoplastic pathway of water transport in roots, forcing water to enter the symplast.

 

Question 3. Which of the following is present in monocot leaves?
A. Bulliform cell
B. Leaf base
C. Bundle sheath
D. Resin gland
E. Water cavity
(a) A, B, C, E
(b) A, B, D, E
(c) A, B, E
(d) A, B, C
Answer: (d) A, B, C
In simple words: Monocot leaves have special bulliform cells, a clear leaf base, and a bundle sheath around their veins. These features help them adapt to their environment.

🎯 Exam Tip: Bulliform cells help in the rolling and unrolling of leaves to reduce water loss, a key adaptation in monocots.

 

Question 4. A vascular bundle in which phloem is on both sides of the xylem is said to be:
(a) Collateral open
(b) Bicollateral open
(c) Concentric
(d) Bicollateral closed
Answer: (b) Bicollateral open
In simple words: When a vascular bundle has xylem in the middle with phloem on both its inner and outer sides, it's called a bicollateral vascular bundle. If it also has cambium, it's an 'open' type.

🎯 Exam Tip: Bicollateral vascular bundles are a specific type, often found in plants like Cucurbitaceae (cucumber family), indicating a more complex arrangement of vascular tissues.

 

Question 5. Presence of cuticle is a common character of:
A. Monocot stem
B. Dicot stem
C. Monocot root
D. Dicot root
E. Monocot leaf
F. Dicot leaf
(a) A, B, E, F
(b) B, F
(c) A, B, C, D, E, F
(d) A, E, F
Answer: (a) A, B, E, F
In simple words: A cuticle, which is a protective waxy layer, is commonly found on the outer surfaces of both monocot and dicot stems, as well as on monocot and dicot leaves. It helps prevent water loss.

🎯 Exam Tip: The cuticle is a crucial adaptation for land plants, reducing water evaporation from plant surfaces and protecting against pathogens.

III. Fill in the Blanks:

 

Question 1. .......... is known as "Father of Plant Anatomy".
Answer: Nehemiah Grew
In simple words: Nehemiah Grew is considered the "Father of Plant Anatomy" because he was a pioneer in studying the internal structure of plants. His detailed work laid the foundation for this field.

🎯 Exam Tip: Knowing key historical figures in science helps understand the development of biological fields and the origins of our current knowledge.

 

Question 2. .......... are the group of cells that are similar or dissimilar in structure and origin, but perform similar function.
Answer: Tissues
In simple words: Tissues are groups of cells that work together to do a specific job, even if they look a little different. They are the building blocks of organs in plants and animals.

🎯 Exam Tip: Defining tissues as groups of cells with a common function is a fundamental concept in biology, essential for understanding organismal structure.

 

Question 3. Based on the ability to divide, tissues are classified into ........... and ........... tissue.
Answer: Meristematic and Permanent
In simple words: Plant tissues are split into two main kinds: meristematic, which are always dividing and growing, and permanent, which have stopped dividing and do fixed jobs.

🎯 Exam Tip: Differentiating between meristematic and permanent tissues is crucial for understanding plant growth patterns and development.

 

Question 4. .......... is the outermost layer.
Answer: Epidermis
In simple words: The epidermis is the outer protective layer of a plant, like skin, covering stems, roots, and leaves. It helps protect the plant from harm and water loss.

🎯 Exam Tip: The epidermis acts as the first line of defense for plants, making its structural and protective functions very important in survival.

 

Question 5. The main function of vascular tissue system are transport of .......... and ..........
Answer: Water and Food
In simple words: The vascular tissue system in plants works like a transport system, carrying water from the roots up to the leaves and moving food made in the leaves to other parts of the plant.

🎯 Exam Tip: The vascular tissue system, primarily xylem (water) and phloem (food), is essential for the survival and growth of all higher plants.

 

Question 6. .......... and .......... forms the ground tissue system.
Answer: inner
In simple words: The ground tissue system, which makes up most of the plant body, is found in the inner part of the plant structure. It performs functions like storage, support, and photosynthesis.

🎯 Exam Tip: The ground tissue system is versatile, forming the bulk of the plant and supporting various metabolic processes beyond just structural support.

 

Question 7.
Answer: Cortex, Endodermis, Pericycle and Pith
In simple words: The stele, which is the central part of the root, contains these important tissues: cortex, endodermis, pericycle, and pith. They work together for transport and support.

🎯 Exam Tip: Understanding the components of the stele is fundamental to plant anatomy and helps in differentiating root types.

 

Question 8. Epiblema is also known as ......... or ..........
Answer: Rhizodermis or Piliferous layer
In simple words: Epiblema, the outermost layer of roots, is also called rhizodermis or piliferous layer because it often has root hairs. It helps in absorbing water and minerals.

🎯 Exam Tip: The terms "rhizodermis" and "piliferous layer" emphasize the root-specific functions and structures associated with the outermost layer.

 

Question 9. ........... helps in the movement of water and dissolved salts from cortex into xylem.
Answer: Casparian strips
In simple words: Casparian strips are waxy bands that control how water and minerals move from the cortex into the xylem. They ensure water passes through cells, not just between them.

🎯 Exam Tip: Casparian strips are critical for regulating the entry of water and dissolved nutrients into the vascular cylinder, acting as a selective barrier.

 

Question 10. The tissue present between xylem and phloem is called ..........
Answer: Conjunctive tissue
In simple words: The tissue found between the xylem and phloem in a plant's vascular bundle is called conjunctive tissue. It helps to connect these two important transport tissues.

🎯 Exam Tip: Conjunctive tissue is a parenchymatous tissue that fills the spaces between the vascular bundles and can sometimes differentiate into cambium.

 

Question 11. All the tissues inner to endodermis constitute ..........
Answer: Stele
In simple words: The stele is the central part of the stem or root, containing all the tissues located inside the endodermis. This includes vascular tissues and sometimes pith.

🎯 Exam Tip: The stele is a fundamental concept in plant anatomy, representing the primary vascular structure and its associated ground tissues.

 

Question 12. The tissue present between the upper and lower epidermis is called ..........
Answer: Hypodermis
In simple words: In some plant stems, the tissue directly below the epidermis is called the hypodermis. It often provides support or protection to the stem.

🎯 Exam Tip: The hypodermis is an extra protective layer in many plants, offering mechanical support and sometimes helping to store water.

 

Question 13. Reaction centres and the accessory pigments together are called ..........
Answer: Photosystems
In simple words: In photosynthesis, reaction centers and other helper pigments team up to form structures called photosystems. These systems capture light energy.

🎯 Exam Tip: Photosystems are complex structures embedded in the thylakoid membranes where light energy is converted into chemical energy.

 

Question 14. Light reaction takes place in .......... membrane of the chloroplast.
Answer: Thylakoid lumen
In simple words: The light-dependent reactions of photosynthesis happen within the thylakoid membranes inside the chloroplasts. This is where sunlight is turned into chemical energy.

🎯 Exam Tip: Thylakoid membranes contain chlorophyll and other pigments that absorb light energy, initiating the process of photosynthesis.

 

Question 15. Kreb cycle is also known as ..........
Answer: Tricarboxylic Acid Cycle (TCA)
In simple words: The Krebs cycle, an important part of respiration, is also called the Tricarboxylic Acid Cycle or TCA cycle. It helps break down food to release energy.

🎯 Exam Tip: Knowing alternative names for metabolic cycles like the Krebs cycle (also called citric acid cycle) is useful for broader biological understanding.

 

Question 16. Glycolysis take place in .......... of the cell.
Answer: Cytoplasm
In simple words: Glycolysis, the first step in breaking down glucose for energy, happens in the cytoplasm of a cell. This process doesn't need oxygen.

🎯 Exam Tip: Glycolysis is a universal metabolic pathway, occurring in almost all organisms and representing the initial stage of glucose breakdown.

 

Question 17. Krebs cycle occurs in .......... matrix.
Answer: Mitochondria
In simple words: The Krebs cycle takes place in the matrix of the mitochondria, which are like the powerhouses of the cell. This is where more energy is extracted from food molecules.

🎯 Exam Tip: The localization of metabolic pathways (like glycolysis in cytoplasm, Krebs cycle in mitochondrial matrix) is crucial for understanding cellular respiration.

 

Question 18. The gas evolved during photosynthesis is ..........
Answer: Oxygen
In simple words: During photosynthesis, plants use sunlight to make food and release oxygen gas into the air. This oxygen is vital for most living things.

🎯 Exam Tip: Oxygen is a crucial byproduct of photosynthesis, making this process fundamental to sustaining aerobic life on Earth.

 

Question 19. The first step in aerobic respiration is ..........
Answer: Glycolysis
In simple words: Glycolysis is the very first step in aerobic respiration, where glucose is broken down into smaller molecules. It happens before oxygen is even used.

🎯 Exam Tip: While glycolysis doesn't require oxygen, it's the initiating step for both aerobic and anaerobic respiration pathways.

 

Question 20. Energy currency of cells is ...........
Answer: ATP
In simple words: ATP (Adenosine Triphosphate) is like the energy money for cells. Cells use ATP to power almost all their activities, from moving to building new parts.

🎯 Exam Tip: ATP is often called the "energy currency" because it provides readily usable energy for various cellular processes.

 

Question 21. Major functions of epiblema is ..........
Answer: Protection
In simple words: The main job of the epiblema, the outer layer of roots, is protection. It shields the inner tissues from harm and helps in absorbing water and minerals.

🎯 Exam Tip: The protective function of outer tissue layers like the epiblema (in roots) or epidermis (in stems/leaves) is essential for plant survival in harsh environments.

IV. Match the Following:

Answer:
A. (iv) Nicotinamide Adenine Dinucleotide phosphate
B. (iii) Absence of light
C. (i) Anaerobic
D. (v) Collenchyma
E. (ii) Monocot
In simple words: This section matches biological terms from Column I with their correct descriptions or related terms from Column II. For example, NADP is a key molecule in photosynthesis, the Calvin cycle is a light-independent process, and ground tissue is often made of collenchyma.

🎯 Exam Tip: When matching, carefully read both columns and identify key terms or definitions to ensure accurate pairing, especially for technical biological terms.

V. Answer in a Sentence:

 

Question 1. What are the functions of Epidermis?
Answer:

• The epidermis protects the inner surface.
• Stomata help in transpiration.
• Root hairs help in absorption of water and minerals.

This outermost layer of cells plays crucial roles in safeguarding the plant and facilitating essential life processes.
In simple words: The epidermis is the outer protective layer of a plant. It keeps the inside safe, helps with water release (transpiration) through stomata, and root hairs help absorb water.

🎯 Exam Tip: When listing functions, use clear bullet points for readability and remember to include a range of functions such as protection, gas exchange, and absorption.

 

Question 2. Name the factors which affect photosynthesis.
Answer: The process of photosynthesis is affected by both internal and external factors. Internally, pigments, leaf age, carbohydrate accumulation, and hormones play a role. Externally, light, carbon dioxide, temperature, water, and minerals are key influences. Understanding these factors helps us see how plants optimize their food production.
In simple words: Photosynthesis is affected by things inside the plant like how old its leaves are or how many pigments it has. It's also affected by outside things like sunlight, carbon dioxide in the air, temperature, water, and minerals.

🎯 Exam Tip: When discussing factors affecting biological processes, it's good practice to categorize them (e.g., internal vs. external) for a comprehensive answer.

 

Question 3. What are Oxysomes?
Answer: Oxysomes are minute, regularly spaced, tennis racket-shaped particles found on the inner mitochondrial membrane. They are involved in the synthesis of ATP (adenosine triphosphate), the energy currency of the cell. These tiny structures are essential for producing energy efficiently within the mitochondria.
In simple words: Oxysomes are tiny, racket-shaped parts on the inner lining of mitochondria. They are like small energy factories, helping cells make ATP, which is their main form of energy.

🎯 Exam Tip: When defining cellular structures, include their location, shape/appearance, and primary function for a complete description.

 

Question 4. What is Cortex?
Answer: The cortex is the region located below the epidermis in a plant stem or root. Its primary function is to store starch, providing a reserve of energy for the plant. This layer forms a significant part of the ground tissue system.
In simple words: The cortex is the layer found just under the outer skin (epidermis) of plant stems and roots. Its main job is to store food like starch for the plant.

🎯 Exam Tip: Clearly defining anatomical terms by their location and primary function is essential for accurate answers in botany questions.

 

Question 5. What is Pericycle?
Answer: The pericycle is the outermost layer of the stele, which is the central vascular cylinder of a plant. It is composed of a single layer of thin-walled cells. This layer is crucial because it gives rise to lateral roots. This tissue plays a vital role in root development.
In simple words: The pericycle is the outer layer of the central part (stele) of a root. It is made of thin cells and is where new side roots grow from.

🎯 Exam Tip: Emphasize the pericycle's role in the formation of lateral roots, as this is its most distinctive and important function.

 

Question 6. What are the functions of chloroplasts?
Answer:

• Photosynthesis
• Storage of starch
• Synthesis of fatty acids
• Storage of lipids
• Formation of chloroplasts (self-replication)

Chloroplasts are the primary sites for these vital processes, particularly photosynthesis, which sustains plant life.
In simple words: Chloroplasts do many jobs. They make food using sunlight (photosynthesis), store starch, make fats, store fats, and even make more chloroplasts.

🎯 Exam Tip: When listing functions, a comprehensive answer should include both the primary (photosynthesis) and secondary (synthesis/storage) roles of the organelle.

 

Question 7. Where are passage cells located and what is their function?
Answer: Passage cells are specialized endodermal cells located opposite the protoxylem. They have thin walls and lack Casparian strips. Their main function is to facilitate the entry of water from the cortex into the xylem. These cells provide a direct pathway for water transport.
In simple words: Passage cells are special cells in the endodermis of roots, found across from the protoxylem. They have thin walls and no Casparian strips, making it easy for water to move from the outer part of the root into the water-carrying tubes (xylem).

🎯 Exam Tip: Highlighting the absence of Casparian strips in passage cells is key, as this structural feature directly enables their function in water transport.

 

Question 8. What is protoxylem lacuna?
Answer: In a mature vascular bundle, especially in monocot stems, the lowest protoxylem vessels often disintegrate, forming a cavity. This cavity is called a protoxylem lacuna. For example, it is seen in monocot stems. This feature helps in identifying monocots.
In simple words: A protoxylem lacuna is a small empty space or gap that forms in the vascular bundles of some plants, like monocot stems. It happens when the earliest-formed xylem cells break down.

🎯 Exam Tip: Protoxylem lacuna is a diagnostic feature for identifying monocot stems in anatomical studies.

VI. Short Answer Questions:

 

Question 1. Name the three types of plastids.
Answer:
1. Chloroplasts: These are green-colored plastids that help in photosynthesis, producing food for the plant.
2. Chromoplasts: These are yellow, red, or orange-colored plastids that give color to flowers and fruits, attracting pollinators and seed dispersers.
3. Leucoplasts: These are colorless plastids primarily responsible for storing food, such as starch, oils, and proteins. Plastids are vital organelles for various plant functions.
In simple words: The three types of plastids are chloroplasts (green, make food), chromoplasts (red/yellow/orange, color flowers), and leucoplasts (no color, store food).

🎯 Exam Tip: When differentiating plastids, remember to associate each type with its characteristic color (or lack thereof) and primary functional role within the plant cell.

 

Question 2. List out the functions of chloroplast.
Answer:
1. Photosynthesis: Chloroplasts are the primary sites where plants convert light energy into chemical energy, producing glucose.
2. Synthesis of fatty acids: They are involved in the production of fatty acids, essential components of cell membranes.
3. Storage of lipids: Chloroplasts can store lipids, which serve as energy reserves.
4. Storage of starch: They also store starch granules, the main storage form of carbohydrates in plants. These functions make chloroplasts critical for plant metabolism.
In simple words: Chloroplasts do many things: they make food through photosynthesis, create fatty acids, and store both fats and starch.

🎯 Exam Tip: While photosynthesis is the main function, mentioning other roles like synthesis and storage of organic molecules demonstrates a deeper understanding of chloroplast biology.

 

Question 3. What are Concentric bundles? Explain its types.
Answer: Concentric vascular bundles are a type of vascular bundle where either the xylem completely surrounds the phloem or the phloem completely surrounds the xylem. They are of two types:
1. Amphivasal: In this type, the xylem completely surrounds the phloem. An example is Dracaena. The xylem forms a ring around the phloem.
2. Amphicribral: Here, the phloem completely surrounds the xylem. An example is Ferns. The phloem creates a sheath around the xylem.
In simple words: Concentric bundles are when one water-carrying tissue completely wraps around the other. In amphivasal, xylem wraps phloem (like in Dracaena). In amphicribral, phloem wraps xylem (like in Ferns).

🎯 Exam Tip: When defining vascular bundle types, clearly state the arrangement of xylem and phloem and provide distinct examples for each type to illustrate the concept.

 

Question 4. What are photosynthetic pigments?
Answer: Photosynthetic pigments are substances involved in photosynthesis that absorb light energy. There are two main categories:
1. Primary pigment: This pigment, primarily chlorophyll 'a', traps solar energy and converts it into electrical and chemical energy. It is the core molecule for light capture.
2. Accessory pigments: These pigments (like chlorophyll 'b', carotenoids, and xanthophylls) absorb light energy at different wavelengths and pass this absorbed energy to the primary pigment. They broaden the range of light used for photosynthesis. They are crucial for efficient energy capture.
In simple words: Photosynthetic pigments are special colors in plants that catch sunlight. The main one is chlorophyll 'a', which starts the energy making. Other helper pigments gather more light and give it to chlorophyll 'a'.

🎯 Exam Tip: Differentiate between primary and accessory pigments, explaining their specific roles in capturing and transferring light energy during photosynthesis.

 

Question 5. (a) Differentiate between Palisade parenchyma and spongy parenchyma.

Answer: Palisade parenchyma cells are elongated and tightly packed under the upper epidermis, rich in chloroplasts for photosynthesis. Spongy parenchyma cells are irregularly shaped with large air spaces, located below the palisade layer, and primarily aid in gaseous exchange, with fewer chloroplasts. Both are vital for leaf function, but their structure suits different roles.
In simple words: Palisade cells are long and tightly packed at the top of a leaf, full of green parts for making food. Spongy cells are rounder, have gaps, and are at the bottom, helping air move around for breathing.

🎯 Exam Tip: When comparing tissue types, focus on key structural differences (shape, packing, spaces) and their corresponding functional adaptations (photosynthesis vs. gas exchange).

 

Question 5. (b) Differentiate between Monocot leaf and Dicot leaf.

Answer: Monocot leaves are often isobilateral, meaning their upper and lower sides are similar, with palisade parenchyma on both sides and spongy parenchyma centrally located. Dicot leaves are dorsiventral, having distinct upper and lower surfaces, with mesophyll clearly differentiated into palisade and spongy layers. These differences reflect their evolutionary adaptations.
In simple words: Monocot leaves usually look the same on both sides (like grass) and have palisade cells everywhere. Dicot leaves (like sunflower) have a clear top and bottom, with different cell layers for making food and air exchange.

🎯 Exam Tip: When distinguishing monocot and dicot leaves, focus on symmetry (isobilateral vs. dorsiventral) and the organization of the mesophyll tissue.

 

Question 6. Define stele.
Answer: The stele is the central part of the plant stem or root, located inner to the endodermis. It is comprised of the pericycle and the entire vascular system (xylem and phloem). Essentially, the stele contains all the primary vascular tissues. This central core is responsible for transport and often for structural support.
In simple words: The stele is the central core of a plant's root or stem. It includes the pericycle and all the tubes that carry water and food (vascular bundles).

🎯 Exam Tip: Clearly define the stele as encompassing the pericycle and vascular tissues, emphasizing its central location and role in transport.

 

Question 7. Where is the respiratory cavity located?
Answer: The respiratory cavity, also known as the substomatal cavity, is an air space found immediately adjacent to the stomata in plant leaves. This cavity allows for the diffusion of gases like carbon dioxide and oxygen between the atmosphere and the internal cells of the leaf. Its presence is vital for efficient gas exchange.
In simple words: The respiratory cavity is an air space right under the stomata (small holes) in a leaf. It helps gases like carbon dioxide and oxygen move in and out of the leaf easily.

🎯 Exam Tip: Emphasize the proximity of the respiratory cavity to stomata and its role in facilitating efficient gas exchange, which is crucial for photosynthesis and respiration.

 

Question 8. What is an isobilateral leaf? Give an example.
Answer: An isobilateral leaf is a type of leaf in which the mesophyll tissue is not differentiated into distinct palisade parenchyma and spongy parenchyma. Instead, it is composed of only spongy or palisade parenchyma, or both layers are arranged similarly on both sides of the leaf. This results in the upper and lower surfaces of the leaf appearing structurally similar. An example is Grass (Monocot leaf). This structural uniformity is a key characteristic.
In simple words: An isobilateral leaf looks the same on both its top and bottom sides. Its inner tissue (mesophyll) doesn't have two distinct layers like other leaves. Grass is an example of an isobilateral leaf.

🎯 Exam Tip: The lack of clear differentiation between palisade and spongy parenchyma is the defining characteristic of isobilateral leaves, typically found in monocots.

 

Question 9. What is dorsiventral leaf? Give an example.
Answer: A dorsiventral leaf is a type of leaf where the mesophyll tissue is clearly differentiated into palisade parenchyma on the upper (adaxial) side and spongy parenchyma on the lower (abaxial) side. This structural differentiation results in distinct upper and lower surfaces, which often differ in appearance and function. An example is a Dicot leaf. This specialized structure optimizes photosynthesis and gas exchange.
In simple words: A dorsiventral leaf has a clear top and bottom side that look different. The inner tissue is split into two layers: a dense palisade layer on top and a airy spongy layer below. Dicot leaves are examples of this type.

🎯 Exam Tip: Understanding the structural differentiation of mesophyll in dorsiventral leaves helps explain their efficient light capture and gas exchange mechanisms.

 

Question 10. Define tetrarch xylem.
Answer: Tetrarch xylem refers to a condition in a plant's vascular tissue where the xylem forms four distinct groups or arms radiating from the center. The number of protoxylem points (the earliest formed xylem elements) is four. This arrangement is a common characteristic seen in Dicot roots. This pattern is important for distinguishing root types.
In simple words: Tetrarch xylem means that the water-carrying part (xylem) in a plant's root has four distinct arms or groups. This is a special pattern often seen in dicot roots.

🎯 Exam Tip: The number of xylem bundles (e.g., tetrarch, polyarch) is a key anatomical feature used to classify roots as monocot or dicot.

 

Question 11. What are generally called as accessory pigments?
Answer: Accessory pigments are photosynthetic pigments other than chlorophyll 'a' that assist in capturing light energy for photosynthesis. Examples include chlorophyll 'b', carotenoids, and xanthophylls. These pigments absorb light at different wavelengths than chlorophyll 'a' and then transfer that energy to chlorophyll 'a' to broaden the spectrum of light usable for photosynthesis. They are crucial for efficient energy capture.
In simple words: Accessory pigments are extra color molecules in plants, like carotenoids or xanthophylls. They help the main green pigment (chlorophyll 'a') catch more sunlight for making food.

🎯 Exam Tip: Emphasize that accessory pigments broaden the spectrum of light absorbed, thereby increasing the efficiency of photosynthesis in varying light conditions.

 

Question 12. Write any three significance of photosynthesis.
Answer:
1. It is the source of all our food and fuel: Photosynthesis produces glucose, which is the primary source of energy for most life forms on Earth, directly or indirectly. It forms the base of almost all food chains.
2. It drives all other processes of biological and a biological world: The energy captured by photosynthesis powers virtually all ecological systems and biological cycles, including growth, reproduction, and ecosystem dynamics.
3. It is responsible for the growth and sustenance of our biosphere: By producing oxygen and consuming carbon dioxide, photosynthesis maintains the atmospheric composition vital for aerobic life and supports the entire biomass of the planet. It keeps the Earth's ecosystem balanced.
In simple words: Photosynthesis is very important because it makes all our food, gives energy to almost all living things, and keeps the air fresh by making oxygen and using carbon dioxide.

🎯 Exam Tip: When listing the significance of a process, provide points that highlight its impact on life, ecosystems, and global cycles to show a comprehensive understanding.

 

Question 13. What are the functions of epidermal tissue system?
Answer:
1. Epidermis protects the inner tissues: It forms a protective outer layer against physical damage, pathogens, and excessive water loss.
2. Stomata helps in transpiration: Small pores called stomata, located in the epidermis, regulate the exchange of gases and the release of water vapor.
3. Root hairs help in absorption of water and minerals: Specialized epidermal extensions on roots, known as root hairs, significantly increase the surface area for efficient uptake of water and nutrients. This system ensures overall plant health and survival.
In simple words: The epidermis protects the plant inside. Stomata (small openings) help the plant breathe and release water. Root hairs on roots soak up water and food from the soil.

🎯 Exam Tip: When explaining the epidermal tissue system, include its key components (epidermis, stomata, root hairs) and their specific contributions to protection, regulation, and absorption.

 

Question 14. Differentiate between monocot and dicot stem.

Answer: Monocot stems have scattered, closed vascular bundles and undifferentiated ground tissue, often showing protoxylem lacuna. Dicot stems, conversely, feature open vascular bundles arranged in a ring, with clearly differentiated ground tissue into cortex, endodermis, pericycle, and pith, and typically lack protoxylem lacuna. These distinct structural differences aid in their classification and function.
In simple words: Monocot stems have their water and food tubes scattered and closed, and the inside tissue is all the same. Dicot stems have their tubes in a circle, and the inside tissue is split into different parts.

🎯 Exam Tip: When differentiating monocot and dicot stems, focus on the arrangement and nature of vascular bundles and the organization of ground tissue, as these are primary distinguishing characteristics.

VII. Long Answer Questions:

 

Question 1. Explain Epidermal tissue system.
Answer: The epidermal tissue system forms the outermost protective covering of plants. It consists primarily of the epidermis, which is a single layer of cells covering the entire plant body. Associated with the epidermis are specialized structures like epidermal outgrowths, stomata, and root hairs. Epidermis cells are closely packed to form a barrier. Stomata are minute pores, often interrupted by guard cells, that regulate gas exchange and transpiration. Root hairs are extensions of epidermal cells on roots, increasing the surface area for water and mineral absorption. Additionally, the epidermis is covered by a waxy cuticle in aerial parts to check water evaporation. This complex system ensures protection, gas regulation, and nutrient uptake, vital for plant survival and growth.
In simple words: The epidermal tissue system is like the plant's skin. It includes the outer layer (epidermis) which protects the plant, tiny holes (stomata) for breathing and releasing water, and root hairs that soak up water and nutrients from the soil. It also has a waxy coat (cuticle) to stop water loss.

🎯 Exam Tip: A comprehensive explanation of the epidermal tissue system should cover its main components (epidermis, stomata, root hairs, cuticle) and their collective roles in protection, regulation, and absorption.

 

Question 2. Explain the types of Vascular bundle.
Answer: Vascular bundles are structures containing xylem and phloem, arranged in various ways within a plant. They are crucial for transporting water and nutrients. There are three main types:
1. Radial Vascular Bundle: In this type, xylem and phloem are arranged on different radii, alternating with each other. This arrangement is characteristic of roots. For example, roots have radial vascular bundles, ensuring efficient water and nutrient uptake.
2. Conjoint Vascular Bundle: Here, xylem and phloem are arranged side-by-side on the same radius. These are further divided into two types:
    (a) Collateral Vascular Bundles: In collateral bundles, xylem and phloem are arranged on the same radius, with the phloem typically towards the outside and xylem towards the inside. These are common in stems and leaves. Collateral bundles can be:
        i. Open collateral vascular bundle: This type includes cambial tissue between the xylem and phloem, allowing for secondary growth. An example is the Dicot stem.
        ii. Closed collateral vascular bundle: This type lacks cambium between the xylem and phloem, thus preventing secondary growth. An example is the Monocot stem.
    (b) Bicollateral Vascular Bundle: In bicollateral bundles, phloem is present on both the outer and inner sides of the xylem. This arrangement is seen in plants like Cucurbita. It's a more complex form of collateral bundle.
3. Concentric Vascular Bundle: In these bundles, one vascular tissue completely surrounds the other. They are of two types:
    (a) Amphivasal: The xylem completely surrounds the phloem. An example is Dracaena.
    (b) Amphicribral: The phloem completely surrounds the xylem. An example is Ferns. These arrangements ensure specialized transport needs.
In simple words: Vascular bundles are like tubes that carry water and food in plants. They come in three main kinds: radial (xylem and phloem side by side but on different lines, like in roots), conjoint (xylem and phloem on the same line, like in stems), and concentric (one wraps around the other). Conjoint bundles can be open (with growth tissue) or closed (no growth tissue), and some are bicollateral (phloem on both sides of xylem).

🎯 Exam Tip: When describing vascular bundles, it's crucial to explain the relative positions of xylem and phloem for each type and provide specific plant examples to illustrate the concept.

 

Question 3. Explain the Primary structure of Monocot root.
Answer: The internal structure of a monocot root includes several layers. These layers are Epiblema/Rhizodermis, Cortex, Endodermis, and Stele.

🎯 Exam Tip: When explaining anatomical structures, always list the main layers or parts first before describing each in detail to provide a clear overview.

 

The structure of monocot root can be described as follows:
1. Epiblema/Rhizodermis:
• This is the outermost layer of the monocot root. It protects the root.
• It is made of a single layer of thin-walled, parenchymatous cells.
• Root hairs grow from this layer, helping in the absorption of water and minerals from the soil.
• Stomata and cuticle (a waxy protective layer) are not present on the root, as its main job is absorption.
• Its main function is to protect the inner tissues.
2. Cortex:
• This region lies just below the epidermis. It is a wide area.
• It is made up of only parenchymatous cells, which have spaces between them (intercellular spaces).
• The cortex is a multi-layered structure.
• Its main function is to store water and food material for the plant.
3. Endodermis:
• This is the innermost layer of the cortex. It separates the cortex from the central vascular tissue.
• It forms a complete ring around the stele, which includes special Casparian strips and Passage cells.
• Casparian strips are band-like thickenings made of suberin, which control water and nutrient movement into the stele.
4. Stele:
• This is the central part of the root, found inner to the endodermis. It contains the essential transport systems.
• It includes the pericycle, vascular bundles, and pith.
(a) Pericycle:
• This is the outermost layer of the stele. It is made of a single layer of tightly arranged parenchymatous cells.
• Its main function is to help in the origin of lateral roots.
(b) Vascular bundles:
• The vascular tissue (xylem and phloem) is arranged in a radial pattern.
• The xylem is exarch (protoxylem towards the periphery) and polyarch (many xylem bundles).
• The conjunctive tissue, located between the xylem and phloem, is sclerenchymatous (has thick walls for support).
(c) Pith:
• This is a large central part, made of parenchyma cells with intercellular spaces.
• Its function is to store starch. Monocot roots usually have a large and well-developed pith.
In simple words: A monocot root has layers like an outer skin (epiblema), a middle fleshy part (cortex), a boundary layer (endodermis), and a central core (stele). The stele has the water and food pipes (vascular bundles) and a storage center (pith). Each part helps the root grow and absorb things.

🎯 Exam Tip: Remember that monocot roots typically have a well-developed pith and polyarch xylem arrangement, distinguishing them from dicot roots.

 

Question 4. Draw the structure of Dicot root.
Answer: Refer to the diagram below.
In simple words: The question asks for a drawing of a dicot root's internal structure. You need to sketch its different layers like the epidermis, cortex, endodermis, and vascular bundles.

🎯 Exam Tip: When drawing, focus on clear labeling of all parts, especially the tetrarch xylem and absence of a prominent pith, which are key features of dicot roots.

 

Question 5. Describe the Primary structure of T.S of Monocot stem.
Answer: The primary structure of a monocot stem, when cut across (T.S.), shows different layers and arrangements. These include the epidermis, hypodermis, ground tissue, and vascular bundles.
(i) Epidermis:
• This is the outermost protective layer of the monocot stem.
• It is made up of a single layer of tightly packed parenchyma cells.
• A few stomata (small pores) are present in the epidermis, allowing for gas exchange.
• Multicellular hairs are typically absent in monocot stems.
(ii) Hypodermis:
• This layer is located directly below the epidermis.
• It is made up of sclerenchymatous cells, which provide mechanical support and strength to the stem.
• This layer might be interrupted by chlorenchyma (cells with chloroplasts) in some areas.
(iii) Ground tissue:
• Unlike dicot stems, monocot stems do not have distinct cortex, endodermis, pericycle, or pith.
• Instead, there is an undifferentiated mass of parenchyma cells that forms the entire central part of the stem.
• This ground tissue helps in storage and some basic metabolic functions.
(iv) Vascular bundles:
• The vascular bundles (xylem and phloem) are scattered throughout the ground tissue, rather than being arranged in a ring.
• Each vascular bundle is surrounded by a sclerenchymatous bundle sheath, which provides protection.
• These bundles are conjoint (xylem and phloem together), collateral (xylem and phloem side-by-side), endarch (protoxylem towards the center), and closed (no cambium for secondary growth).
• Xylem contains both metaxylem (larger vessels) and protoxylem (smaller vessels). In mature bundles, the lowest protoxylem often disintegrates, forming a cavity called a protoxylem lacuna.
• Phloem contains sieve tubes and companion cells, which transport food.
(v) Pith:
• The pith is not clearly differentiated as a separate region in monocot stems; it is part of the general ground tissue.
In simple words: A monocot stem has a protective outer layer (epidermis), a strengthening layer beneath it (hypodermis), and a large, undivided central part called the ground tissue. Inside this ground tissue, the water and food pipes (vascular bundles) are scattered and not in a neat ring.

🎯 Exam Tip: Key features to highlight for monocot stem structure are the scattered vascular bundles, the sclerenchymatous hypodermis, and the undifferentiated ground tissue.

 

Question 6. Write a short note on structure of chloroplast.
Answer: Chloroplasts are special green structures within plant cells where photosynthesis takes place. They are vital for plant survival.
(i) Chloroplasts are the actual sites where photosynthesis happens, turning sunlight into energy.
(ii) These are green plastids (a type of organelle) because they contain a green pigment called chlorophyll.
(iii) A chloroplast mainly consists of an outer envelope, an inner stroma, and internal structures called thylakoids and grana.
Envelope: The chloroplast is surrounded by two membranes: an outer and an inner envelope membrane, with a space between them.
Stroma: This is the fluid-filled space (matrix) inside the inner membrane. It contains DNA, ribosomes (70S type), and other molecules needed for making proteins and carrying out the dark reactions of photosynthesis.
Thylakoids: These are flattened, disc-like sacs inside the stroma. The space inside a thylakoid is called the thylakoid lumen. Thylakoids are where the light-dependent reactions of photosynthesis occur. Some thylakoids are stacked on top of each other to form structures called grana (singular: granum). These grana are connected by other membranes called stromal lamellae or fret channels.
In simple words: Chloroplasts are like tiny green factories in plants. They have two main parts: a watery space called stroma and stacks of small discs called grana (made of thylakoids). The green color comes from chlorophyll, which helps plants use sunlight to make food.

🎯 Exam Tip: Remember the three main parts of a chloroplast (envelope, stroma, thylakoids/grana) and their roles in light-dependent and light-independent reactions for a complete answer.

 

Question 7. Explain the primary structure of T.S Dicot stem.
Answer: The internal structure of a dicot stem, when viewed in a transverse section (T.S.), shows distinct arrangements of tissues.
(i) Epidermis :
• This is the outermost protective layer of the dicot stem.
• Its outer wall is covered by a thick cuticle, which helps to prevent water loss through transpiration.
• It has a few stomata (pores) and multicellular hairs (trichomes) present on its surface.
(ii) Cortex :
The cortex in a dicot stem is well-differentiated into three main zones:
• Hypodermis: This is the layer just below the epidermis. It is made up of a few layers of collenchymatous cells, which provide mechanical strength and flexibility to the young stem.
• Middle cortex: This part, inner to the hypodermis, consists of a few layers of chlorenchymatous tissue. These cells contain chloroplasts and can perform photosynthesis.
• Inner cortex: This innermost layer of the cortex is made of parenchyma cells, which store food materials. The innermost layer of the cortex is also called the endodermis. These cells are compactly arranged in barrel-shaped cells and often contain starch grains, so this layer is also called the starch sheath.
(iii) Stele :
The stele is the central vascular cylinder, located inner to the endodermis. It includes the pericycle, vascular bundles, and pith.
• Pericycle: A few layers of sclerenchyma cells are found in patches outside the phloem in each vascular bundle. These cells provide support.
• Vascular bundle: Vascular bundles in a dicot stem are arranged in a ring. They are conjoint (xylem and phloem together), collateral (xylem and phloem side-by-side), endarch (protoxylem towards the center), and open (with cambium between xylem and phloem, allowing for secondary growth).
• Pith: This is the large, central part of the stem, composed of parenchyma cells with intercellular spaces. Its main function is to store food.
In simple words: A dicot stem has an outer skin (epidermis), a middle part (cortex) with strengthening cells and food-making cells, and a central core (stele). In the stele, the water and food pipes (vascular bundles) are neatly arranged in a ring, and there's a storage center called the pith.

🎯 Exam Tip: When describing dicot stem, always mention the distinct ring arrangement of vascular bundles, the presence of cambium for secondary growth, and the differentiated cortex layers.

 

Question 8. Describe the structure of T.S of dicot leaf.
Answer: A dicot leaf, when cut in transverse section (T.S.), shows distinct differences between its upper and lower sides, making it dorsiventral.
The T.S. of a dicot leaf contains three main parts:
(i) Epidermis – Upper and Lower:
• Upper Epidermis: This is the outermost layer on the upper side of the leaf. It is made up of a single layer of tightly packed parenchyma cells. A thicker cuticle covers this layer to reduce water loss.
• Lower Epidermis: This is the outermost layer on the lower side of the leaf. It is also made of a single layer of parenchymatous cells, but with a thinner cuticle. Stomata are more numerous in the lower epidermis compared to the upper epidermis. These stomata are used for transpiration (water vapor release) and gaseous exchange.
(ii) Mesophyll :
The region between the upper and lower epidermis is called mesophyll. This tissue is specialized for photosynthesis and is differentiated into two types of parenchyma:
• Palisade parenchyma: These cells are located directly below the upper epidermis. They are elongated and arranged compactly, without intercellular spaces. They contain a high number of chloroplasts, making them the primary site of photosynthesis.
• Spongy parenchyma: These cells are located above the lower epidermis. They are irregularly shaped and have large intercellular spaces between them. They contain fewer chloroplasts than palisade cells. Their primary function is gaseous exchange, facilitated by the air spaces.
(iii) Vascular bundles :
• Vascular bundles are the veins of the leaf, containing xylem and phloem for transport. They are conjoint, collateral, and closed.
• These bundles are surrounded by a compact layer of parenchymatous cells called the bundle sheath. This sheath helps to protect the vascular tissue.
• The xylem is typically located towards the upper (adaxial) epidermis, while the phloem is towards the lower (abaxial) epidermis.
In simple words: A dicot leaf has an outer skin (epidermis) on both top and bottom. Inside, there's a middle layer called mesophyll, which has two types of cells: long palisade cells on top for making food, and spongy cells below them with air pockets for breathing. Small pipes (vascular bundles) run through the leaf to carry water and food.

🎯 Exam Tip: Remember that dicot leaves are dorsiventral, meaning they have distinct upper and lower sides due to the differentiation of mesophyll into palisade and spongy layers.

 

VIII. Higher Order Thinking Skills (Hots)

 

Question 1. The cells of endodermis show band like thickening on their radial and inner tangential walls called casparian strips. Why?
Answer: The Casparian strips are present in the endodermis cells to prevent the re-entry of water into the cortex once water has moved into the xylem tissue. They act like a barrier, ensuring that all water and dissolved minerals must pass through the endodermal cells' cytoplasm, allowing the plant to regulate what enters its vascular system.
In simple words: Casparian strips stop water from leaking back into the outer part of the root. They make sure water has to go through special cells to reach the center, giving the plant control over what it absorbs.

🎯 Exam Tip: Emphasize that Casparian strips enforce the apoplastic pathway block, forcing water and solutes into the symplastic pathway for selective absorption.

 

Question 2. Do plants like Croton, with non-green leaves have chlorophyll and do they perform photosynthesis?
Answer: Yes, plants like Croton, even with their non-green leaves, do have chlorophyll and perform photosynthesis. The chlorophyll is present in the Croton leaves but is often hidden by other colored pigments like carotenoids (yellow, orange) and anthocyanin (red, purple). These additional pigments assist or help the pigment chlorophyll in the process of photosynthesis by absorbing different wavelengths of light.
In simple words: Croton plants have green chlorophyll, even if their leaves look red or yellow. Other colors just cover up the green. They still use sunlight to make food because chlorophyll is still working inside.

🎯 Exam Tip: Remember that accessory pigments, while providing color, also aid photosynthesis by capturing light energy and passing it to chlorophyll.

 

Question 3. How do we see beautiful colours in Autumn and enjoy the fall?
Answer: We see beautiful colors in autumn because of changes happening in the leaves. Chlorophyll is the pigment that gives plants their green color and is essential for photosynthesis. During the warmer months (spring and summer), plants have plenty of light and actively produce chlorophyll, which is why leaves appear green.
However, as autumn approaches, the days get shorter and cooler. This means there isn't enough sunlight for photosynthesis to happen as much. So, plants stop making new chlorophyll. The existing green chlorophyll starts to break down and fade away. As the green color disappears, other pigments that were already present in the leaves, but were hidden by the dominant green, become visible. These include yellow and orange colors from carotenoids. Additionally, as photosynthesis stops, sugars trapped in the leaves cause the production of new red and purple pigments called anthocyanins. It's this combination of different colors becoming visible that creates the beautiful yellows, oranges, and reds we enjoy during the fall.
In simple words: In autumn, trees stop making green color (chlorophyll) because there is less sunlight. The hidden yellow and orange colors then show up. New red colors are also made from trapped sugars. All these colors together make autumn leaves look beautiful.

🎯 Exam Tip: Explain that fall colors are due to the breakdown of chlorophyll revealing existing pigments (carotenoids) and the production of new pigments (anthocyanins).