Samacheer Kalvi Class 9 Science Solutions Chapter 19 Plant Physiology

I. Choose the correct answer :

Question 1. The tropic movement that helps the climbing vines to find a suitable support is
(a) phototropism
(b) geotropism
(c) thigmotropism
(d) chemotropism
Answer: (c) thigmotropism
In simple words: When climbing plants, like vines, grow, they need something to hold onto. Thigmotropism is how they move and wrap around a support, like a pole or another plant, to help them climb upwards.

🎯 Exam Tip: Remember that "thigmo-" relates to touch, which helps distinguish thigmotropism from other tropisms like photo- (light) or geo- (gravity).

Question 2. The chemical reaction occurs during photosynthesis is .
(a) CO₂ is reduced and water is oxidized
(b) water is reduced and CO₂ is oxidized
(c) both CO₂ and water are oxidized
(d) both CO₂ and water are produced
Answer: (a) CO₂ is reduced and water is oxidized
In simple words: During photosynthesis, carbon dioxide takes in electrons (gets reduced) and water loses electrons (gets oxidized). This process helps plants make food using sunlight.

🎯 Exam Tip: Recall that "reduction" means gaining electrons or hydrogen, and "oxidation" means losing electrons or hydrogen. In photosynthesis, water gives up electrons to CO₂, making water oxidized and CO₂ reduced.

Question 3. The bending of root of a plant in response to water is called
(a) Thigmonasty
(b) Phototropism
(c) Hydrotropism
(d) Photonasty
Answer: (c) Hydrotropism
In simple words: Hydrotropism is the way plant roots grow specifically towards water sources. Roots need water to survive and grow, so they naturally bend to find it.

🎯 Exam Tip: The prefix "hydro-" always refers to water, making it easy to remember that hydrotropism is about a plant's response to water.

Question 4. A growing seedling is kept in the dark room. A burning candle is placed near it. The seedling bends towards the burning candle. This is an example of
(a) Chemotropism
(b) Geotropism
(c) Phototropism
(d) Thigmotropism
Answer: (c) Phototropism
In simple words: Phototropism is when a plant part moves or grows towards light. Even if the light comes from a candle in a dark room, the seedling will bend towards that light source.

🎯 Exam Tip: The main energy source for plants is light, so phototropism ensures that plant shoots grow towards light to maximize photosynthesis.

Question 5. The root of the plant is
i) positively phototropic but-negatively geotropic
ii) positively geotropic but negatively phototropic
iii) negatively phototropic but positively hydrotropic
iv) negatively hydrotropic but.positively phototropic
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: (b) (ii) and (iii)
In simple words: Plant roots typically grow downwards, pulled by gravity (positive geotropism), and grow away from light (negative phototropism). They also grow towards water (positive hydrotropism).

🎯 Exam Tip: Remember the primary functions of roots: anchorage and water absorption. Their responses to stimuli are geared towards these roles.

Question 6. The non-directional movement of a plant part in response to temperature is called.
(a) Thermotropism
(b) Thermonasty
(c) Chemotropism
(d) Thigmonasty
Answer: (b) Thermonasty
In simple words: Thermonasty is when a plant part moves because of temperature changes, but the direction of movement does not depend on where the temperature is coming from. For example, some flower petals open or close depending on how warm or cool it is.

🎯 Exam Tip: Nastic movements are non-directional (e.g., flowers opening/closing), while tropic movements are directional (e.g., stems growing towards light).

Question 7. Chlorophyll in a leaf is required for
(a) photosynthesis
(b) tropic movement
(c) transpiration
(d) nastic movement
Answer: (a) photosynthesis
In simple words: Chlorophyll is the green substance in plant leaves. Its main job is to capture sunlight, which is the energy plants need to make their own food through a process called photosynthesis.

🎯 Exam Tip: Chlorophyll absorbs light energy, primarily red and blue light, and reflects green light, which is why most leaves appear green.

Question 8. Transpiration takes place through
(a) fruit
(b) seed
(c) flower
(d) stomata
Answer: (d) stomata
In simple words: Transpiration is when plants release water vapor into the air. This mostly happens through tiny holes on their leaves called stomata.

🎯 Exam Tip: Stomata are important for gas exchange (taking in CO₂ and releasing O₂) as well as for water release, which helps pull water up the plant from the roots.

II. Fill in the blanks :

Question 1. The shoot system grows upward in response to light.
Answer: light
In simple words: The part of the plant above the ground, like the stem and leaves, grows upwards to reach sunlight.

🎯 Exam Tip: This upward growth towards light is a type of tropism called phototropism, which is essential for photosynthesis.

Question 2. Root is positively hydrotropic as well as positively geotropic.
Answer: root
In simple words: A plant's root grows towards water (hydrotropic) and also grows downwards into the soil because of gravity (geotropic).

🎯 Exam Tip: Roots growing towards water helps the plant absorb essential nutrients, while growing downwards provides stability.

Question 3. The green pigment present in the plant is chlorophyll.
Answer: chlorophyll
In simple words: Plants are green because of a special color substance called chlorophyll. This substance is very important for making food.

🎯 Exam Tip: Chlorophyll's green color comes from it absorbing most light colors except green, which it reflects.

Question 4. The solar tracking of sunflower in accordance with the path of sun is due to phototropism.
Answer: phototropism
In simple words: Sunflowers turn their heads to follow the sun's path across the sky. This movement is called phototropism, which means "light turning."

🎯 Exam Tip: This tracking helps the sunflower capture as much sunlight as possible for photosynthesis throughout the day.

Question 5. The response of a plant part towards gravity is geotropism.
Answer: geotropism
In simple words: When a part of a plant grows either towards or away from the pull of gravity, this kind of movement is known as geotropism. Roots grow down with gravity, and stems grow up against it.

🎯 Exam Tip: Geotropism ensures that roots grow into the soil for water and nutrients, and shoots grow upwards for sunlight.

Question 6. Plants take in carbon dioxide for photosynthesis but need oxygen for their living.
Answer: oxygen
In simple words: Plants use carbon dioxide to make food, but just like animals, they also need to breathe in oxygen to stay alive.

🎯 Exam Tip: This highlights that plants perform both photosynthesis (making food) and respiration (breathing) like other living organisms.

III. Match column A with column B

Answer:
1. Roots growing downwards into soil - Positive geotropism
2. Shoots growing towards the light - Positive phototropism
3. Shoots growing upward - Negative geotropism
4. Roots growing downwards away from light - Negative phototropism
In simple words: This table matches how different parts of a plant respond to things like gravity and light. For example, roots grow down because of gravity (positive geotropism), and shoots grow towards light (positive phototropism).

🎯 Exam Tip: Remember that "positive" means growing towards a stimulus, and "negative" means growing away from it. "Geotropism" is gravity, "phototropism" is light.

IV. State whether true or false. If false, write the correct statement:

Question 1. The response of a part of plant to the chemical stimulus is called phototropism.
Answer: False.
Correct statement: The response of a plant part to the chemical stimulus is called chemotropism.
In simple words: Plants can respond to chemicals, and that movement is called chemotropism, not phototropism, which is about light.

🎯 Exam Tip: Be careful not to confuse different types of tropisms. Each prefix (photo-, geo-, hydro-, chemo-, thigmo-) points to a specific stimulus.

Question 2. Shoot is positively phototropic and negatively geotropic.
Answer: True.
In simple words: The shoot (stem and leaves) of a plant grows towards light, which is positive phototropism. It also grows upwards, against gravity, which is negative geotropism.

🎯 Exam Tip: This dual response helps the shoot optimize its position for photosynthesis by reaching sunlight while standing upright.

Question 3. The petals of moon flower open up in morning and closes in the evening. This is called photonasty.
Answer: False.
Correct statement: The petals of moon flower open up in the evening and close in the morning. This is called photonasty.
In simple words: Moonflowers open their petals when it's dark, in the evening, and close them when the sun comes out in the morning. This light-related movement is photonasty.

🎯 Exam Tip: Photonasty is a nastic movement (non-directional) triggered by changes in light intensity, like the opening and closing of certain flowers.

Question 4. Photosynthesis produces glucose and carbon dioxide.
Answer: False.
Correct statement: Photosynthesis produces glucose and oxygen.
In simple words: Plants make their food, which is a sugar called glucose, and they also release oxygen gas during photosynthesis. They do not produce carbon dioxide.

🎯 Exam Tip: Always remember the inputs (carbon dioxide, water, sunlight) and outputs (glucose, oxygen) of photosynthesis accurately.

Question 5. Photosynthesis is important in releasing oxygen to keep the atmosphere in balance.
Answer: True.
In simple words: Photosynthesis helps keep the air healthy by giving out oxygen, which is needed by many living things.

🎯 Exam Tip: This highlights the crucial ecological role of photosynthesis in maintaining breathable air on Earth.

Question 6. Plants lose water when the stomata on leaves are closed.
Answer: False.
Correct statement: Plants lose water when the stomata on leaves are open.
In simple words: Water leaves a plant through tiny openings called stomata. If these stomata are closed, the plant cannot lose water vapor.

🎯 Exam Tip: Stomata open during the day to allow carbon dioxide in for photosynthesis, but this also leads to water loss (transpiration).

V. Answer very briefly :

Question 1. What is nastic movement?
Answer: Nastic movements are the non-directional responses of plant parts to a stimulus. This means the direction of the movement is not determined by the direction of the stimulus. For example, a flower opening in the morning is a nastic movement.
In simple words: Nastic movement is when a plant moves in response to something, but the direction it moves does not depend on where the push or pull came from.

🎯 Exam Tip: Contrast nastic movements (non-directional, like folding leaves) with tropic movements (directional, like growing towards light).

Question 2. Name the plant part
a) Which bends in the direction of gravity but away from the light.
b) Which bends towards the light but away from the force of gravity.
Answer:
a) Root system
b) Shoot system.
In simple words: The roots grow down towards gravity and away from light. The shoots (stems and leaves) grow up towards light and away from gravity.

🎯 Exam Tip: Remember that roots primarily seek water and anchorage (influenced by gravity), while shoots seek light for photosynthesis.

Question 3. Differentiate phototropism from photonasty.
Answer:
Phototropism:
1. This is the movement of a plant part towards light. It is a directional growth movement.
2. An example is the shoot of a plant growing towards a light source.
Photonasty:
1. This is a movement of a plant part in response to light intensity, but it is a non-directional movement.
2. An example is the moonflower's petals opening in the evening light and closing in the morning light.
In simple words: Phototropism means a plant part grows towards light in a specific direction. Photonasty means a plant part moves because of light, but not in a specific direction.

🎯 Exam Tip: The key difference is directionality: tropic movements are directional, nastic movements are non-directional.

Question 4. Photosynthesis converts energy X into energy Y.
a) What are X and Y?
b) Green plants are autotrophic in their mode of nutrition. Why?
Answer:
a) X represents light energy, and Y represents chemical energy. Plants transform light energy into chemical energy during photosynthesis.
b) Green plants are considered autotrophic because they have the ability to produce their own food materials through the process of photosynthesis. They use simple inorganic substances like carbon dioxide and water to make complex organic food.
In simple words: a) X is light energy, and Y is chemical energy. b) Green plants make their own food using sunlight, so they are called autotrophs.

🎯 Exam Tip: Autotrophs are self-feeders, producing their own food; heterotrophs consume other organisms for food. Photosynthesis is the prime example of autotrophic nutrition.

Question 5. Define transpiration.
Answer: Transpiration is the process where plants lose water in the form of water vapor from their aerial parts, primarily through tiny pores called stomata on the leaves. This process is essential for water transport and cooling.
In simple words: Transpiration is when plants release water vapor from their leaves into the air.

🎯 Exam Tip: Transpiration creates a "pull" that helps draw water and nutrients from the soil up through the plant stems to the leaves.

Question 6. Name the cell that surrounds the stoma.
Answer: Each stoma (plural: stomata) is surrounded by two specialized cells called guard cells. These cells control the opening and closing of the stomata.
In simple words: Guard cells are the cells that go around each stoma. They control if the stoma is open or closed.

🎯 Exam Tip: Guard cells regulate gas exchange and water loss, making them critical for the plant's survival.

VI. Answer briefly :

Question 1. Give the technical terms for the following :
a) Growth dependent movement in plants.
b) Growth independent movement in plants.
Answer:
a) Tropic movements are growth-dependent movements in plants. These movements involve actual growth in a specific direction.
b) Nastic movements are growth-independent movements in plants. These movements do not involve growth and can be reversible.
In simple words: a) Movements that involve growing in a certain direction are called tropic movements. b) Movements that don't involve growing and can happen quickly are called nastic movements.

🎯 Exam Tip: A good way to remember is that "tropic" movements are usually slow, permanent growth, while "nastic" movements are often rapid, temporary changes (like opening and closing).

Question 2. Explain the movement seen in Pneumatophores of Avicennia.
Answer: In plants like Avicennia, which grow in marshy or waterlogged soils, specialized roots called pneumatophores are observed. These roots grow vertically upwards, out of the soil and water, reaching into the air. They are involved in the respiration of the plant. These roots have tiny holes called lenticels through which they take in gases from the atmosphere, helping the plant breathe in oxygen, which is scarce in waterlogged soil.
In simple words: Avicennia plants live in wet places and have special roots called pneumatophores. These roots grow upwards out of the mud to help the plant get air, like breathing tubes, because there is not much air in the waterlogged soil.

🎯 Exam Tip: Pneumatophores are a unique adaptation for plants in mangrove swamps or other oxygen-poor environments, allowing them to respire effectively.

Question 3. Fill in the blanks:
\( 6CO₂ + 12H₂O \xrightarrow{Sunlight \atop Chlorophyll} C₆H₁₂O₆ + 6H₂O + 6O₂↑ \)
Answer: \( 6CO₂ + 12H₂O \xrightarrow{Sunlight \atop Chlorophyll} C₆H₁₂O₆ + 6H₂O + 6O₂↑ \)
In simple words: This equation shows how plants use carbon dioxide and water with sunlight and chlorophyll to make sugar (their food), water, and oxygen.

🎯 Exam Tip: Memorize the balanced chemical equation for photosynthesis, including the role of sunlight and chlorophyll, as it's fundamental to understanding plant life.

Question 4. What is chlorophyll?
Answer: Chlorophyll is the green pigment found in the chloroplasts of plant cells. It is crucial for photosynthesis as it absorbs light energy from the sun. This absorbed energy is then used to convert carbon dioxide and water into glucose (sugar) and oxygen.
In simple words: Chlorophyll is the green coloring in plants that catches sunlight. This sunlight helps plants make their food.

🎯 Exam Tip: Chlorophyll is the key molecule that makes plants appear green and is the first step in the entire food chain on Earth.

Question 5. Name the part of plant which shows positive geotropism. Why?
Answer: The root of a plant shows positive geotropism. This occurs because the root grows downwards, in the same direction as the gravitational force. This ensures that the root is properly anchored in the soil and can access water and minerals present deep underground.
In simple words: The root of a plant grows downwards because of gravity. This helps the root stay firm in the ground and find water and food.

🎯 Exam Tip: Positive geotropism in roots is vital for plant stability and nutrient absorption, showing how plants adapt to their environment.

Question 6. What is the difference between the movement of flowers in the sunflower plant and the closing of the leaves in the Mimosa pudica?
Answer: The movements in sunflower plants and Mimosa pudica differ in their nature and type of response:
Movement in Sunflower Plant (Phototropism):
The stem tip of a sunflower plant follows the path of the sun from dawn to dusk (East to West) and moves from West to East during the night. This is a growth movement, meaning the plant physically grows in the direction of the light stimulus. It is an example of phototropism, a tropic movement.
Closing of leaves in Mimosa pudica (Thigmonasty/Seismonasty):
The closing of leaves in Mimosa pudica (touch-me-not plant) occurs quickly in response to touch or vibrations. This is not a growth movement; it happens independently of the direction of the stimulus. It is a nastic movement, specifically thigmonasty (response to touch) or seismonasty (response to shock/vibration). This rapid movement is due to changes in turgor pressure within specialized cells.
In simple words: Sunflower flowers slowly turn to face the sun as it moves across the sky; this is a growth movement towards light. Mimosa pudica leaves quickly fold up when touched; this is a fast, non-growth movement caused by changes in water pressure inside cells.

🎯 Exam Tip: Differentiate between tropic movements (slow, growth-related, directional) and nastic movements (fast, non-growth-related, non-directional) using these classic examples.

Question 7. Suppose you have a rose plant growing in a pot, how will you demonstrate transpiration in it?
Answer: To demonstrate transpiration in a rose plant, follow these steps:
1. Take a potted rose plant and water it well.
2. Cover one or more leaves of the plant with a transparent plastic bag. Tie the opening of the bag securely around the stem to prevent water from entering or escaping from the soil.
3. Place the potted plant in sunlight for a few hours.
4. After some time (e.g., 2-3 hours), you will observe small droplets of water condensing on the inner surface of the plastic bag.
This condensation shows that the plant has released water vapor from its leaves, which then cooled and turned into liquid water inside the bag. This process is transpiration.
In simple words: To see transpiration, put a clear plastic bag over a rose plant's leaves and leave it in the sun. After a while, you will see small water drops inside the bag, showing the plant released water.

🎯 Exam Tip: Ensure the plastic bag is clear to allow light for the plant and that it's tied tightly to isolate the leaf area, making the experiment conclusive.

Question 8. Mention the differences between stomatal and lenticular transpiration.
Answer: Transpiration occurs through different plant structures, primarily stomata and lenticels:
Stomatal Transpiration:
1. This is the loss of water from plants through tiny pores called stomata, which are mainly found on the surface of leaves.
2. The majority of transpiration (about 90-95%) in a plant takes place through stomata.
3. It is regulated by guard cells that control the opening and closing of stomata.
Lenticular Transpiration:
1. This is the loss of water from plants as vapor through lenticels. Lenticels are small, porous openings found on the bark of woody stems, branches, and some fruits.
2. Only a very small percentage of water is lost through lenticular transpiration (typically less than 1%).
3. It is a continuous process and cannot be regulated by the plant, unlike stomatal transpiration.
In simple words: Stomatal transpiration is when plants lose most of their water through small holes on leaves called stomata, which can open and close. Lenticular transpiration is when a small amount of water is lost through tiny openings on woody stems called lenticels, which cannot be controlled.

🎯 Exam Tip: Focus on the location (leaves vs. woody stems) and the ability to regulate water loss (stomata controlled, lenticels not) as key differentiating points.

Question 9. To which directional stimuli do (a) roots respond (b) shoots respond?
Answer:
(a) Roots respond to directional stimuli in the following ways:
- Positively geotropic: They grow towards the force of gravity (downwards).
- Negatively phototrophic: They grow away from light.
- Positively hydrotropic: They grow towards water.
(b) Shoots (stems and leaves) respond to directional stimuli as follows:
- Negatively geotropic: They grow against the force of gravity (upwards).
- Positively phototrophic: They grow towards light.
- Negatively hydrotropic: They generally grow away from water, although this response is less pronounced than for roots.
In simple words: a) Roots grow down with gravity and towards water, but away from light. b) Shoots grow up against gravity and towards light, but generally away from water.

🎯 Exam Tip: Understand that roots and shoots often show opposite responses to the same stimuli, which helps the plant optimize its different parts for survival and growth.

VII. Answer in detail :

Question 1. Differentiate between tropic and nastic movements
Answer: The main differences between tropic and nastic movements in plants are:
Tropic Movements:
1. These are directional growth movements in response to a stimulus. The direction of growth is determined by the direction of the stimulus.
2. They are growth-dependent movements, meaning the plant actually grows in a certain direction.
3. They are usually more or less permanent and irreversible, as they involve changes in growth pattern.
4. Tropic movements are commonly found in all higher plants.
5. The action is generally slow, often taking hours or days to be noticeable.
Nastic Movements:
1. These are non-directional movements of plant parts in response to a stimulus. The direction of movement is independent of the direction of the stimulus.
2. They are growth-independent movements, meaning they do not involve permanent growth changes.
3. They are temporary and reversible, often caused by changes in turgor pressure.
4. Nastic movements are typically found only in a few specialized plants, such as the touch-me-not plant.
5. The action can be very fast, sometimes occurring within seconds or minutes.
In simple words: Tropic movements are slow and cause parts of the plant to grow towards or away from something, like light or gravity. Nastic movements are faster, do not involve growth, and the plant part moves without caring where the push or pull came from.

🎯 Exam Tip: Think of tropic movements as long-term adjustments for growth and survival, while nastic movements are often short-term responses to immediate environmental changes.

Question 2. How will you differentiate the different types of transpiration?
Answer: There are three main types of transpiration, each differing in the plant part involved and the extent of water loss:
1. Stomatal Transpiration:
- This is the most common type, accounting for about 90-95% of total water transpired from a plant.
- It occurs through tiny pores called stomata, primarily located on the leaves.
- Stomatal opening and closing are regulated by guard cells, allowing the plant to control water loss and gas exchange.
2. Cuticular Transpiration:
- This is the loss of water directly from the outer surface of the leaves and stems, through a waxy layer called the cuticle.
- It accounts for a smaller percentage of total transpiration, typically around 5-10%.
- The cuticle helps to reduce water loss, but some water still diffuses through it.
3. Lenticular Transpiration:
- This type involves the loss of water vapor through small, raised pores called lenticels, which are found on the bark of woody stems and branches.
- It accounts for a very small percentage of total water loss, often less than 1%.
- Lenticels are not regulated by guard cells, so water loss through them is continuous.
Transpiration is essential for several reasons: It creates a pull in the leaf and stem, which helps in the absorption of water and minerals by roots. It also helps regulate the plant's temperature by evaporative cooling.
In simple words: Plants lose water in three main ways: most water leaves through tiny holes on leaves (stomatal), a little bit escapes through the waxy skin of leaves (cuticular), and a very small amount goes out through small bumps on woody stems (lenticular).

🎯 Exam Tip: Focus on the location and regulatory mechanisms (or lack thereof) for each type of transpiration when differentiating them.

VIII. Higher Order Thinking Skills :

Question 1. While conducting experiments to study the effects of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X however bends " away from stimulus A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to factors related with Earth. Keeping these points in mind, answer the following questions:
(a) What could be stimulus A ?
(b) Name the stimulus seen in B.
(c) What could be stimulus-C?
Answer:
(a) Stimulus A is Water.
(b) Stimulus B is Gravity.
(c) Stimulus C is Light.
In simple words: The roots of the plant grow towards water and gravity but away from light. The stem of the plant grows away from water and gravity but towards light.

🎯 Exam Tip: This question tests your understanding of positive and negative tropisms for both roots and shoots concerning common environmental stimuli.

Question 2. An organism A which cannot move from one place to another makes a simple food B from the substances C and D available in the environment. This food is made in the presence of green coloured substance E present in organs F in the presence of light energy in a process called G. Some of the simple food B also gets converted into a complex food H for storage purposes. This food gives blue-black colour with iodine solution?
(a) What is (i) organism A (ii) food B and food H?
(b) Name (i) green coloured substance E and organ F.
(c) Name the process G.
Answer:
(a) (i) Organism A refers to Green plants.
(ii) Food B is Glucose.
Food H is Starch.
(b) Green coloured substance E is Chlorophyll.
Organ F is Leaves.
(c) Process G is Photosynthesis.
In simple words: a) Organism A is a green plant. Food B is glucose, and food H is starch. b) The green substance E is chlorophyll, found in organ F, which are leaves. c) Process G is photosynthesis.

🎯 Exam Tip: This question summarizes the entire process of photosynthesis, from reactants and products to the organisms and cellular structures involved.

Activity - 1

Intext Activities

Take a glass trough and fill it with sand. Keep a flower pot containing water, plugged at the bottom at the centre of the glass trough. Place some soaked pea or bean seeds around the pot in the sand. What do you observe after 6 or 7 days? Record your observation.

Aim: To demonstrate hydrotropism.

Materials required : Glass trough, sand, flower pot, plugged at the bottom, pea or bean seeds and water.

Procedure:

1. A glass trough is taken and is filled with sand. A flowerpot containing water plugged at the bottom is kept at the centre of the glass trough.

2. Soaked pea or bean seeds are placed around the pot in the sand. It is observed after 6 or 7 days.

Observation: Observed that radicle has grown towards the pot and moisture instead of growing vertically downward.

Inference: It proves that primary root is positively hydrotropic.

Result: Hydrotropism has been demonstrated by showing positive hydrotropism in roots.

Activity - 2

Take pea seeds soaked in water overnight. Wait for the pea seeds to germinate. Once the seedling has grown put it in a box with an opening for light on one side. After few hours, you can clearly see how the stem has bent and grown towards the light.

Aim: To demonstrate phototropism.

Materials required : Box, water, light and pea seeds.

Procedure:

1. Take pea seeds soaked in water overnight. Wait for the pea seeds to germinate.

2. Once the seedling has grown put it in a box with an opening for light on one side.

3. After few hours, you can clearly see how the stem has bent and grown towards the light.

Observation: Observed that movement of a stem of a plant (pea seeds) towards light moist condition. This is the way a new plant develops from a seed.

Inference : Positive phototropism of a plant has been demonstrated.

Activity - 3

Pluck a variegated leaf from Coleus plant kept in sunlight. De-starch it by keeping in dark room for 24 hours. Draw the picture of this leaf and mark the patches of chlorophyll on the leaf. Immerse the leaf in boiling water followed by alcohol and test it for starch using iodine solution. Record your observation.

Aim: To show that chlorophyll is essential for photosynthesis.

Materials required : Plant with variegated leaves, boiling water, alcohol and iodine solution.

Procedure:

Variegated leaf is plucked from Coleus plant kept in sunlight. It is de-starched by keeping it in dark room for 24 hours. The picture of this leaf is drawn and the patches of chlorophyll on the leaf are marked. After immersing the leaf in boiling water followed by alcohol it is tested for starch with iodine solution.

Observation : The patches of the leaf with chlorophyll turn blue-black. The other portions remain colourless.

Inference: The chlorophyll is essential for photosynthesis.

Activity - 4

Place a potted plant in a dark room for about 2 days to de-starch its leaves. Cover one of its leaves with the thin strip of black paper as shown in the picture, make sure that the leaf is covered on both sides. Keep the potted plant in bright sunlight for 4 to 6 hours. Pluck the selected covered leaf and remove the black paper. Immerse the leaf in boiling water for a few minutes and then in alcohol to remove chlorophyll. Test the leaf now with iodine solution for the presence of starch. The covered part of the leaf does not turn blue-black whereas the uncovered part of the leaf turns blue-black colour. Why are the changes in colour noted in the covered and uncovered part of the leaf?

Aim: To show that light is essential for photosynthesis.

Materials required : Covered leaf, boiling water, alcohol and iodine.

1. A potted plant is placed in a dark room for about 2 days to de-starch its leaves.

2. One of its leaves is covered with a thin strip of black paper as shown in the picture.

3. Make sure that the leaf is covered on both sides.

4. The potted plant is kept in bright sunlight for 4 to 6 hours.

5. The selected covered leaf is plucked and the black paper is removed.

6. The leaf is immersed in boiling water for a few minutes and then in alcohol to remove chlorophyll.

7. The leaf is now tested with iodine solution for the presence of starch.

Observation: The covered part of the leaf does not turn blue-black whereas the uncovered part of the leaf turns blue black colour. The covered part of the leaf which did not receive sunlight was unable to synthesize starch.

Inference : The light is essential for photosynthesis.

9th Science Guide Plant Physiology In Animals Additional Important Questions And Answers

I. Choose The Correct Answer :

Question 1. The bending of root of a plant in response to water is called ............
(a) thigmonasty
(b) phototropism
(c) hydrotropism
(d) photonasty
Answer: (c) hydrotropism
In simple words: Hydrotropism is when a plant root bends towards water. This helps the plant get the water it needs to grow.

🎯 Exam Tip: Remember "hydro" means water. Always link the prefix to the stimulus for tropic movements.

Question 2. A growing seedling is kept in the dark room. A burning candle is placed near it for a few days. The top part of the seedling bends towards the burning candle. This is an example of ............
(a) chemotropism
(b) thigmotropism
(c) phototropism
(d) geotropism
Answer: (c) phototropism
In simple words: When a plant seedling bends towards light from a candle, it shows phototropism. Plants naturally move towards light to help them make food.

🎯 Exam Tip: Phototropism is the movement towards light. Even if the light source is unusual (like a candle), the principle remains the same.

Question 3. The root of the plant is ............
(i) positively phototropic but-negatively geotropic
(ii) positively geotropic but negatively phototropic
(iii) negatively phototropic but positively hydrotropic
(iv) negatively hydrotropic but positively phototropic
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: (b) (ii) and (iii)
In simple words: Plant roots grow downwards (positive geotropism) and away from light (negative phototropism). They also grow towards water (positive hydrotropism) and away from light.

🎯 Exam Tip: Always remember that roots grow down (with gravity) and towards water, while shoots grow up (away from gravity) and towards light.

Question 4. The plant part which exhibits negative geotropism is ............
(a) root
(b) stem
(c) branch
(d) leaves
Answer: (b) stem
In simple words: Negative geotropism means growing away from gravity. The stem of a plant always grows upwards, against the pull of gravity.

🎯 Exam Tip: Geotropism refers to the plant's response to gravity. Roots show positive geotropism (grow down), and stems show negative geotropism (grow up).

Question 5. The non-directional movement of a plant part in response to temperature is called...........
(a) thermotropism
(b) thermonasty
(c) chemotropism
(d) thigmonasty
Answer: (b) thermonasty
In simple words: When a plant part moves because of temperature, but the direction of movement doesn't depend on where the temperature change came from, it is called thermonasty. This is different from bending towards or away from a heat source.

🎯 Exam Tip: Nastic movements are always non-directional, meaning the plant responds regardless of the stimulus's direction. Tropisms are directional.

Question 6. Sunflowers open their petals in bright light during the day time but close the petals in dark at night. This response of sunflowers is called ............
(a) geonasty
(b) thigmonasty
(c) chemonasty
(d) photonasty
Answer: (d) photonasty
In simple words: Sunflowers opening and closing their petals based on light is a type of movement called photonasty. It's a non-directional response to light changes, like flowers blooming in the day.

🎯 Exam Tip: Photonasty is a common nastic movement where plants react to changes in light intensity, such as daily opening and closing of flowers.

Question 7. During photosynthesis plants exhale ............
(a) Carbon dioxide
(b) oxygen
(c) hydrogen
(d) helium
Answer: (b) oxygen
In simple words: Plants take in carbon dioxide and water to make their food during photosynthesis. During this process, they release oxygen into the air, which we breathe.

🎯 Exam Tip: Always remember the basic photosynthesis equation: Carbon Dioxide + Water + Light Energy → Glucose + Oxygen. Oxygen is the byproduct exhaled.

Question 8. Chlorophyll in a leaf is required for ............
(a) photosynthesis
(b) transpiration
(c) tropic movement
(d) nastic movement
Answer: (a) photosynthesis
In simple words: Chlorophyll is the green pigment in plants that helps them capture sunlight. This captured energy is then used to make food through photosynthesis.

🎯 Exam Tip: Chlorophyll is vital because it absorbs light energy, making it the primary pigment for photosynthesis. Without it, plants cannot make their own food.

Question 9. A plant is kept in a dark room for about 24 hours before conducting any experiment on photosynthesis in order to ............
(a) remove chlorophyll from the leaf
(b) remove starch from the leaves
(c) ensure that photosynthesis occurred
(d) to prove transpiration
Answer: (b) remove starch from the leaves
In simple words: Plants are kept in the dark before photosynthesis experiments to make sure all the starch already stored in their leaves is used up. This way, any new starch found after the experiment must have been made during the experiment.

🎯 Exam Tip: De-starching is a crucial first step in photosynthesis experiments, ensuring that only newly synthesized starch is detected, providing clear results.

Question 10. Transpiration takes place through ............
(a) fruit
(b) seed
(c) flower
(d) stomata
Answer: (d) stomata
In simple words: Transpiration is when plants release water vapor. This usually happens through tiny holes on their leaves called stomata, which open and close to control gas and water exchange.

🎯 Exam Tip: Stomata are the primary sites for gas exchange and water loss (transpiration) in plants, acting like tiny regulated pores.

Question 11. Thigmonasty can be seen in ............
(a) Mimosa pudica
(b) Taraxacum officinale
(c) Ipomea alba
(d) Rhizophora
Answer: (a) Mimosa pudica
In simple words: Mimosa pudica, also known as the "touch-me-not" plant, shows thigmonasty. Its leaves quickly fold up when touched, which is a rapid, non-directional response to touch.

🎯 Exam Tip: Thigmonasty is a non-directional movement in response to touch or mechanical vibration, famously demonstrated by the Mimosa pudica plant.

Question 12. The venus flytrap plants are examples for ............
(a) chemotropism
(b) thigmonasty
(c) hydrotropism
(d) thigmotropism
Answer: (b) thigmonasty
In simple words: Venus flytrap plants snap shut their leaves when an insect touches them. This fast closing is a non-directional response to touch, which is called thigmonasty.

🎯 Exam Tip: Carnivorous plants like the Venus flytrap use thigmonasty for prey capture, showcasing rapid movements that are not dependent on the direction of the stimulus.

Question 13. ............ flowers bloom as the temperature increases.
(a) Rose
(b) Jasmine
(c) Lilly
(d) Tulip
Answer: (d) Tulip
In simple words: Tulip flowers are known for opening their petals when the temperature rises. This change in their petals based on temperature is a type of movement called thermonasty.

🎯 Exam Tip: Temperature-induced movements in flowers are examples of thermonasty, where the response is to temperature changes rather than its direction.

Question 14. Only green plants have the unique capacity to release ............ into the atmosphere.
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) ozone
Answer: (b) oxygen
In simple words: Green plants are special because they can take carbon dioxide from the air and give out oxygen. This process, called photosynthesis, is crucial for most living things on Earth.

🎯 Exam Tip: Plants are often called the "lungs of the Earth" because they are the primary producers of atmospheric oxygen through photosynthesis, which is essential for aerobic respiration.

Question 15. The end product of photosynthesis is ............
(a) glucose
(b) sucrose
(c) fructose
(d) none of the options
Answer: (a) glucose
In simple words: During photosynthesis, plants convert light energy into chemical energy. The first sugar they make is glucose, which they then use for energy or store as starch.

🎯 Exam Tip: Glucose is the initial and simplest sugar produced during photosynthesis, forming the basis for plant energy and carbohydrate storage.

II. Fill In The Blanks :

Question 1. The minerals like nitrogen, potassium and phosphorus, are required in substantial quantity by the plants are called ............
Answer: macronutrients
In simple words: Plants need certain minerals in large amounts to grow well. These important minerals, like nitrogen, potassium, and phosphorus, are called macronutrients.

🎯 Exam Tip: Macronutrients are essential plant nutrients needed in relatively large quantities for healthy growth and development, playing roles in various metabolic processes.

Question 2. The solar tracking of sunflower in accordance with the path of sun is due to ............
Answer: phototropism
In simple words: Sunflowers turn their heads to follow the sun's path across the sky. This movement towards sunlight is an example of phototropism, helping them absorb more light for photosynthesis.

🎯 Exam Tip: Heliotropism, or solar tracking, is a specific type of phototropism where plants align their leaves or flowers with the sun's direction.

Question 3. The response of a plant part towards gravity is ............
Answer: geotropism
In simple words: When a plant part grows or moves in response to gravity, it's called geotropism. Roots usually grow downwards (positive geotropism), while stems grow upwards (negative geotropism).

🎯 Exam Tip: Geotropism is crucial for plant establishment, ensuring roots anchor the plant and access water and nutrients, while shoots grow towards light.

Question 4. When the leaves of a sensitive plant are touched with a finger, they fold up and when light fades at dusk the petals of a sunflower. These two plants show ............ and ............ movements.
Answer: thigmonastic, photonastic
In simple words: The sensitive plant folds its leaves when touched (thigmonasty), and sunflowers close their petals when it gets dark (photonasty). Both are types of movements that don't depend on the direction of the touch or light.

🎯 Exam Tip: These examples highlight the two main types of nastic movements: thigmonasty (response to touch) and photonasty (response to light intensity).

Question 5. Opening and closing of Moon flower is not a tropism because the movement in this is ............ independent of stimulus
Answer: independent
In simple words: The Moon flower opens and closes its petals, but this movement is called nastism, not tropism. This is because the movement happens regardless of the direction from which the light stimulus comes.

🎯 Exam Tip: Distinguish between tropisms (directional, growth-related) and nastic movements (non-directional, often reversible, not necessarily growth-related) in plant responses.

Question 6. The raw materials for photosynthesis are ............ and ............
Answer: carbon dioxide, water
In simple words: For plants to make food, they need two main ingredients: carbon dioxide from the air and water from the soil. These are their essential raw materials for photosynthesis.

🎯 Exam Tip: Photosynthesis requires carbon dioxide, water, and light energy. Glucose and oxygen are the products of this vital process.

Question 7. When iodine solution is added for testing starch, part of the leaf with ............ turn blue-black colour.
Answer: starch
In simple words: If you add iodine solution to a leaf, any part that contains starch will change color to blue-black. This color change is a clear sign that starch is present.

🎯 Exam Tip: The iodine test is a common and reliable method to detect the presence of starch; a positive result is indicated by a distinct blue-black color.

Question 8. In leaves, the food is stored in the form of ............
Answer: starch
In simple words: After plants make sugar through photosynthesis, they often change it into starch. This starch is then stored in the leaves or other parts of the plant as a way to keep food for later use.

🎯 Exam Tip: Starch serves as the primary energy storage polysaccharide in plants, allowing them to store excess glucose for periods when photosynthesis is not active.

Question 9. Plants may inhale carbon dioxide for photosynthesis but need ............ for their living.
Answer: oxygen
In simple words: Plants breathe in carbon dioxide for making food, but just like animals, they also need oxygen for respiration to get energy for their daily life processes.

🎯 Exam Tip: Remember that while plants produce oxygen during photosynthesis, they also require oxygen for cellular respiration, a process that occurs continuously to release energy from food.

Question 10. Plants utilize only ............% of the absorbed water for photosynthesis and the other activities.
Answer: 1
In simple words: Plants take in a lot of water, but they actually use only a tiny amount, about 1%, for photosynthesis and other functions. Most of the water they absorb is released back into the air.

🎯 Exam Tip: The vast majority of water absorbed by plants is lost through transpiration, with only a small fraction being used for metabolic processes like photosynthesis and maintaining turgor.

Question 11. Plants inhale and exhale continuously through the ............
Answer: stomata
In simple words: Plants take in and let out gases like carbon dioxide and oxygen all the time. This happens through very small pores, mostly on their leaves, called stomata.

🎯 Exam Tip: Stomata are specialized pores on the plant surface that regulate gas exchange and water vapor release, essential for photosynthesis and transpiration.

Question 12. The bending of shoot towards light is due to the hormone ............
Answer: auxin
In simple words: Plant shoots bend towards light because of a special plant hormone called auxin. Auxin helps cells grow longer, and when it moves to the shaded side of the stem, it makes that side grow faster, causing the stem to bend towards the light.

🎯 Exam Tip: Auxins are key plant hormones responsible for cell elongation and play a central role in phototropism, gravitropism, and apical dominance.

Question 13. Heliotropism is a kind of ............
Answer: phototropism
In simple words: Heliotropism is a specific type of phototropism where plants, like sunflowers, move to follow the sun's path. It's their way of responding to light by orienting towards it.

🎯 Exam Tip: While all heliotropism is phototropism, not all phototropism is heliotropism. Heliotropism implies a continuous tracking movement in response to the sun.

Question 14. The ............ plant exhibits one of the fastest known nastic movements.
Answer: Mimosa pudica
In simple words: The Mimosa pudica, often called the "touch-me-not" plant, is famous for its very fast leaf movements. Its leaves quickly fold inwards when touched, which is a type of nastic movement.

🎯 Exam Tip: The rapid folding of Mimosa pudica leaves is a classic example of thigmonasty, a quick, non-directional response to touch, involving changes in turgor pressure.

Question 15. Chlorophyll differs from haemoglobin by the presence of its central molecule ............
Answer: magnesium
In simple words: Chlorophyll, which gives plants their green color, and hemoglobin, which makes our blood red, are similar in structure but have different central metal atoms. Chlorophyll has magnesium at its center, while hemoglobin has iron.

🎯 Exam Tip: Understanding the central metal atom (magnesium in chlorophyll, iron in hemoglobin) is a key point in distinguishing these two vital biological pigments.

Question 16. Plants exchange gases ............ continuously through these stomata.
Answer: CO2 to O2
In simple words: Plants constantly take in carbon dioxide and release oxygen. This exchange of gases, vital for both photosynthesis and respiration, happens through tiny openings on their leaves called stomata.

🎯 Exam Tip: Gas exchange (carbon dioxide intake, oxygen release) is a continuous process in plants, driven by stomatal opening and closing, and is essential for their survival.

Question 17. Guard cells help in regulating the ............
Answer: rate of transpiration
In simple words: Guard cells are special cells that surround the stomata on plant leaves. They control how wide the stomata open and close, which in turn regulates how much water vapor a plant loses, known as the rate of transpiration.

🎯 Exam Tip: Guard cells are crucial for maintaining water balance within a plant by controlling the stomatal aperture, thereby impacting both transpiration and CO2 uptake.

III. Analogy :

Question 1. Towards a stimulus : Positive tropism :: Away from the stimulus : Negative tropism
Answer: Positive tropism
In simple words: If a plant part grows towards something, it's a positive tropism. If it grows away from something, it's a negative tropism. These terms describe the direction of growth in relation to a stimulus.

🎯 Exam Tip: The terms "positive" and "negative" indicate the direction of the plant's growth response relative to the stimulus (towards or away).

Question 2. Hydrotropism : Response towards water :: Phototropism : ............
Answer: Response towards light
In simple words: Hydrotropism is when plants respond to water. Similarly, phototropism is when plants respond to light, often by growing towards it.

🎯 Exam Tip: Each "-tropism" term describes a plant's directional growth response to a specific stimulus; remembering the prefixes (hydro-water, photo-light) is helpful.

Question 3. Photosynthesis : ............ :: Transpiration : Stomata
Answer: Chlorophyll
In simple words: Just as transpiration (water loss) happens through stomata, photosynthesis (food making) relies on chlorophyll. Chlorophyll is the green pigment that captures sunlight for this process.

🎯 Exam Tip: This analogy highlights key components or locations for major plant processes. Chlorophyll is the pigment essential for photosynthesis, just as stomata are the pores for transpiration.

IV. State Whether The Following Statements Are True Or False. If False, Write The Correct Statement :

Question 1. Scientific term used to represent the bending of roots towards water is called geotropism.
Answer: False.
Correct statement: The scientific term used to represent the bending of roots towards water is called hydrotropism.
In simple words: This statement is false. When roots bend towards water, it's called hydrotropism, not geotropism. Geotropism is about responding to gravity.

🎯 Exam Tip: Hydrotropism refers specifically to the growth response to water, while geotropism is the growth response to gravity. Keep these distinct.

Question 2. When the leaves of Mimosa pudica plant are touched with the finger, they fold up quickly.
Answer: True.
Correct statement: This is an example of thigmonasty.
In simple words: This statement is true. The Mimosa pudica plant quickly folds its leaves when touched. This rapid movement is a clear example of thigmonasty.

🎯 Exam Tip: The Mimosa pudica is a classic example of thigmonasty, a non-directional plant movement in response to touch or mechanical stimuli.

Question 3. The petals of moon flower open up in morning and closes in the evening. This is called photonasty.
Answer: False.
Correct statement: The petals of moon flower open in the evening and close in the morning. This is called photonasty.
In simple words: This statement is false. Moonflowers open their petals when it's dark in the evening and close them during the day. This light-dependent movement is indeed called photonasty.

🎯 Exam Tip: Photonasty refers to non-directional movements in response to light, and understanding specific plant examples like the Moonflower's night bloom is important.

Question 4. Photosynthesis produces glucose and carbon dioxide.
Answer: False.
Correct statement: Photosynthesis produces glucose and oxygen.
In simple words: This statement is false. Photosynthesis creates glucose (sugar) for the plant and releases oxygen into the air. Carbon dioxide is used by the plant, not produced.

🎯 Exam Tip: A common misconception is confusing the reactants and products of photosynthesis. Carbon dioxide is consumed, and oxygen is released as a byproduct.

V. Assertion and reason :

Question. 1. Assertion (A) : If the plant part moves in the direction of gravity, it is called positive geotropism.
Reason (R) : Stem shows positive geotropism.
(a) A and R are incorrect
(b) A is incorrect, R is correct
(c) A is correct, R is incorrect
(d) Both A and R are correct
Answer: (c) A is correct, R is incorrect
In simple words: The assertion is true because moving towards gravity is positive geotropism. However, the reason is false because stems usually grow upwards, which is negative geotropism, not positive.

🎯 Exam Tip: Remember that roots show positive geotropism (grow down), while shoots show negative geotropism (grow up), which is a key distinction for these types of questions.

Question. 2. Assertion (A) : The loss of excess water from the aerial parts of the plant in the form of water vapour is known as transpiration.
Reason (R) : Stomata of the leaf perform transpiration.
(a) A and R are incorrect
(b) A is incorrect, R is correct
(c) A is correct, R is incorrect
(d) Both A and R are correct
Answer: (d) Both A and R are correct
In simple words: Both the statement that transpiration is water loss from plants as vapor, and that stomata help in this process, are correct. Transpiration is how plants release extra water into the air, mostly through tiny holes called stomata on their leaves.

🎯 Exam Tip: When evaluating Assertion-Reason questions, first check if each statement is individually true, then check if the reason correctly explains the assertion.

VI. Short answer questions :

Question 1. Write the scientific terms used to represent the following:
(a) Growing of roots towards the gravity.
(b) Bending of roots towards the water.
Answer:
(a) Positive geotropism
(b) Positive hydrotropism. This is crucial for plants to access essential nutrients dissolved in water.
In simple words: When roots grow down towards gravity, it's called positive geotropism. When they grow towards water, it's called positive hydrotropism.

🎯 Exam Tip: Distinguish between 'geotropism' (response to gravity) and 'hydrotropism' (response to water) for roots, always specifying 'positive' for their typical growth direction.

Question 2. Observe the given picture.
(a) Identify this plant. What type of special movement is shown by this plant?
(b) What are the other movements seen in this plant?
Answer:
(a) This plant is Mimosa pudica, also known as the "touch-me-not" plant. It shows seismonasty or thigmonasty, which is a rapid folding of leaves when touched. This movement helps protect the plant from harm.
(b) Other movements seen in this plant include nastic movements (not directed towards stimuli) and the closing of leaves during darkness, which reopens in the presence of light. The rapid leaf movement in Mimosa is unique in the plant kingdom and is linked to changes in turgor pressure.
In simple words: The plant is Mimosa pudica, which quickly folds its leaves when touched (thigmonasty). It also shows other non-directional movements like closing leaves at night and opening them in daylight.

🎯 Exam Tip: When identifying plant movements, remember that 'thigmonasty' is a non-directional response to touch, distinct from 'thigmotropism' which is directional growth in response to touch.

Question 3. What is the end product of photosynthesis?
Answer: The end product of photosynthesis is glucose, which is then changed into starch for storage in different parts of the plant. Starch serves as the plant's main energy reserve.
In simple words: Photosynthesis makes glucose sugar, which plants turn into starch and store for energy.

🎯 Exam Tip: Always remember that glucose is the primary product of photosynthesis, which is then often converted to starch for longer-term storage.

Question 4. Name the minute openings seen on the lower surface of the leaf.
Answer: The minute openings seen on the lower surface of the leaf are called stomata. These tiny pores are essential for gas exchange.
In simple words: Small holes on the bottom of leaves are called stomata.

🎯 Exam Tip: Always specify that stomata are found *mostly* on the lower surface of leaves to avoid losing marks.

Question 5. Give the scientific terms for the following:
(a) Growth dependent movement in plants.
(b) Growth independent movement in plants.
Answer:
(a) Growth dependent movement in plants is called tropic movements. These movements are typically slow and permanent.
(b) Growth independent movement in plants is called nastic movements. These movements are often rapid and temporary.
In simple words: Movements that depend on growth are called tropic movements. Movements that don't depend on growth are called nastic movements.

🎯 Exam Tip: Remember 'tropic' for growth-related, directional movements and 'nastic' for non-growth, non-directional movements, often quicker.

Question 6. Study the pictures below and then complete the table by putting a plus (+) if the shoot or root grows towards the stimulus and a minus (-) if it grows away from it.

🎯 Exam Tip: Remember that shoots generally exhibit positive phototropism and negative geotropism, while roots show negative phototropism and positive geotropism, as they grow towards water and anchor the plant.

Question 7. What is the other name for thigmonasty?
Answer: The other name for thigmonasty is seismonasty. Both terms describe rapid plant movements in response to touch or mechanical shock.
In simple words: Thigmonasty is also called seismonasty.

🎯 Exam Tip: Use 'seismonasty' to accurately describe touch-sensitive movements, especially when talking about plants like Mimosa pudica.

Question 8. Which flowering plant shows photonasty just opposite to that of Dandelion?
Answer: Moonflower shows photonasty just opposite to that of Dandelion. Dandelions open in light and close in dark, while moonflowers open at night and close during the day.
In simple words: Moonflowers show photonasty opposite to Dandelions.

🎯 Exam Tip: Keep examples of plants that exhibit 'photonasty' (light-dependent non-directional movement) clear; some open in day, others at night.

Question 9. Give an example for chemotropism.
Answer: An example of chemotropism is the growth of certain fungal hyphae away from a source of water or moisture. The hyphae move in response to chemical signals in the environment. Note: There are no clear evidences of negative hydrotropism.
In simple words: Fungal parts growing away from water is an example of chemotropism.

🎯 Exam Tip: Chemotropism involves growth in response to chemicals; the pollen tube growing towards the ovule is a classic example.

Question 10. Which gas is evolved during photosynthesis?
Answer: Oxygen gas is evolved during photosynthesis. This oxygen is crucial for the respiration of most living organisms.
In simple words: Plants release oxygen gas during photosynthesis.

🎯 Exam Tip: Always remember that oxygen is a byproduct of photosynthesis, released into the atmosphere.

Question 11. Give an example for micronutrients.
Answer: Zinc is an example of a micronutrient required by plants. Micronutrients are needed in smaller amounts but are still essential for healthy plant growth.
In simple words: Zinc is a micronutrient for plants.

🎯 Exam Tip: Differentiate between macronutrients (like N, P, K) and micronutrients (like Fe, Zn, Cu) based on the quantity required by plants.

Question 12. What does a Mimosa pudica plant do in response to touch? What is the phenomenon known as?
Answer: In response to touch, the leaves of the Mimosa pudica plant fold up and droop. This movement is known as seismonasty or thigmonasty. This rapid response is a defense mechanism.
In simple words: When touched, Mimosa pudica leaves fold. This is called seismonasty or thigmonasty.

🎯 Exam Tip: Clearly state both the plant's action (folding and drooping) and the correct scientific term (seismonasty/thigmonasty) for full marks.

Question 13. (i) What happens to the dandelion flower
(a) During the daytime?
(b) At night?
(ii) What is the phenomenon known as?
Answer:
(i) (a) During the daytime, the dandelion flower opens its petals.
(b) At night, the dandelion flower closes its petals. This ensures protection and optimal conditions for pollination.
(ii) This phenomenon is known as photonasty.
In simple words: Dandelion flowers open in the day and close at night. This movement is called photonasty.

🎯 Exam Tip: For photonasty, always explain how the plant responds to light and dark cycles and state the specific term.

Question 14. Define photosynthesis.
Answer: Photosynthesis is the process where green plants make their own food using light energy. The word 'photo' means light, and 'synthesis' means to build. During photosynthesis, light energy is changed into chemical energy. Green plants are called autotrophic because they produce their own food materials through this process. This is the foundation of almost all food chains.
In simple words: Photosynthesis is how green plants use light to make their food, changing light energy into chemical energy.

🎯 Exam Tip: In your definition, ensure you mention green plants, light energy conversion, and food production for a complete answer.

Question 15. Draw the structure of stomata and label the parts.
Answer: The stomata structure consists of two guard cells that surround a pore (stoma). These guard cells contain chloroplasts and are responsible for opening and closing the stomata. Surrounding the guard cells are epidermal cells. A nucleus is typically present within each guard cell, and a vacuole takes up a large portion of its volume.

🎯 Exam Tip: When describing stomata, always mention the guard cells, the central pore, and their role in gas exchange and transpiration for a comprehensive answer.

Question 16. Complete the following table with the different types of tropism:

🎯 Exam Tip: Master the positive and negative responses of roots and shoots to gravity, light, and water, as this is a common topic in plant physiology.

Question 17. Label the diagram with the raw materials and products of photosynthesis.
Answer: The diagram illustrates the inputs (raw materials) and outputs (products) of photosynthesis. It shows sunlight hitting a leaf.

🎯 Exam Tip: Clearly remember that carbon dioxide and water are the raw materials, and glucose and oxygen are the products of photosynthesis. Light energy drives this entire process.

Question 18. Give an example for the movement of plant part which is very quick and can be observed easily.
Answer: A casual touch is enough to make the leaves of Mimosa pudica fold up and droop. This takes place quickly and can be easily observed. This is a classic example of seismonastic movement.
In simple words: The Mimosa pudica plant quickly folds its leaves when touched, which is easy to see.

🎯 Exam Tip: Mimosa pudica is the go-to example for quick, easily observable plant movements due to touch (thigmonasty).

Question 19. Name the cell that surrounds the stoma.
Answer: Guard cells surround the stoma. These specialized cells regulate the opening and closing of the stomatal pore.
In simple words: Guard cells are the cells around the stoma.

🎯 Exam Tip: Always associate guard cells with stomata, as they are key to controlling gas exchange and water loss in plants.

Question 20. Give an example for chemotropism.
Answer: During fertilization, the pollen tube grows down the style in response to sugars present in the style. This is an example of chemotropism, as the pollen tube is guided by chemical signals to reach the ovule. This ensures successful reproduction in flowering plants.
In simple words: When a pollen tube grows down inside a flower towards the ovule because of chemical signals, that is chemotropism.

🎯 Exam Tip: The growth of a pollen tube towards the ovule is a classic and clear example of chemotropism in plants.

Question 21. Give the overall equation for photosynthesis.
Answer: The overall equation for photosynthesis is:
\[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6H_2O + 6O_2 \]
This equation shows that carbon dioxide and water react in the presence of sunlight and chlorophyll to produce glucose, water, and oxygen. The balanced equation summarizes the entire complex process.
In simple words: The equation for photosynthesis is 6 carbon dioxide molecules plus 12 water molecules, with sunlight and chlorophyll, make 1 glucose molecule, 6 water molecules, and 6 oxygen molecules.

🎯 Exam Tip: Memorize the balanced chemical equation for photosynthesis, ensuring all reactants and products are correctly placed and coefficients are accurate.

Question 22. Guard cells of stomata are green but cannot photosynthesize? Give reason.
Answer: Guard cells are green because they contain chlorophyll. However, they cannot photosynthesize effectively because they lack some of the necessary enzymes required for the complete photosynthetic reactions. This limits their ability to produce food independently, even with chlorophyll.
In simple words: Guard cells are green because they have chlorophyll, but they cannot do photosynthesis because they are missing some special parts (enzymes) needed for the whole process.

🎯 Exam Tip: While guard cells contain chlorophyll, their primary role is regulating stomatal opening, and their photosynthetic efficiency is limited by a lack of other key components.

Question 23. Why do roots of halophytes show negative geotropism?
Answer: The roots of halophytes (plants that grow in salty marshy areas) show negative geotropism, meaning they grow upwards (180° upright) from the soil. This upward growth helps them to obtain oxygen for respiration, as the soil in their habitat is often waterlogged and low in oxygen. These specialized roots are called pneumatophores.
In simple words: Halophyte roots grow upwards, against gravity, to get enough oxygen for breathing because the soil where they live has very little air.

🎯 Exam Tip: Remember that negative geotropism in halophyte roots (pneumatophores) is an adaptation to low-oxygen, waterlogged environments.

Question 24. Why do stems show positive phototropism?
Answer:
- Stems show positive phototropism, meaning they grow upwards and towards light. This allows them to get sufficient sunlight for photosynthesis. Sunlight is vital for plants to produce their own food.
- This also helps display their flowers prominently, attracting pollinators, and increases the chance of spreading their seeds for reproduction.
In simple words: Stems grow towards light to get sunlight for making food. This also helps flowers be seen by insects and spread seeds.

🎯 Exam Tip: Focus on the twin benefits of positive phototropism in stems: maximizing light absorption for photosynthesis and enhancing reproductive success.

Question 25. Mention four factors required for photosynthesis?
Answer: The four factors required for photosynthesis are: Chlorophyll, Water, Carbon dioxide, and Light. Each of these components plays a critical role in the conversion of light energy into chemical energy.
In simple words: Photosynthesis needs four things: chlorophyll, water, carbon dioxide, and light.

🎯 Exam Tip: List all four essential factors for photosynthesis; missing any one will result in incomplete marks.

Question 26. Why is transpiration called as necessary evil?
Answer: Transpiration is often called a "necessary evil" because while it involves the loss of a lot of water from the plant, it is still a very important process with several benefits.
- It creates an absorption force in roots, which helps to suck more water from the soil. This "transpirational pull" helps water move up the plant.
- It regulates the temperature of the plant through evaporative cooling, much like sweating in animals. Without it, plants could overheat in direct sunlight.
Therefore, even though water is lost, transpiration is crucial for plant survival.
In simple words: Transpiration is called a "necessary evil" because plants lose a lot of water through it (evil), but it's needed to pull water up from roots and to keep the plant cool (necessary).

🎯 Exam Tip: When explaining why transpiration is a 'necessary evil', clearly state both the 'evil' (water loss) and the 'necessary' benefits (water transport, cooling).

Question 27. What are stomata?
Answer: Stomata are tiny, microscopic pores found mainly on the surface of plant leaves, although they can also be on stems. These pores allow for the exchange of air (gases) between the plant's internal tissues and the atmosphere. Each stoma is surrounded by two specialized cells called guard cells, which regulate the opening and closing of the pore, controlling gas exchange and the rate of transpiration.
In simple words: Stomata are tiny holes on plant leaves that let gases in and out. Guard cells around them control if they are open or closed.

🎯 Exam Tip: Describe stomata as microscopic pores, primarily on leaves, that facilitate gas exchange and transpiration, and mention their regulation by guard cells.

Question 28. Write the scientific terms used to represent.
Answer: When leaves fold up and droop in the touch-me-not plant (Mimosa pudica), the scientific terms used to represent this are thigmonasty or seismonasty. An example of a plant showing this movement is Brunnichia ovata and Mimosa pudica.
In simple words: When leaves like those of the Mimosa pudica plant fold down when touched, it's called thigmonasty or seismonasty.

🎯 Exam Tip: For movements in Mimosa pudica, 'thigmonasty' or 'seismonasty' are the correct terms, indicating a non-directional response to touch or shock.

VII. Long answer questions :

Question 1. Write a note on Transpiration.
Answer: Transpiration is the process where plants lose water in the form of water vapor from their aerial parts, primarily through the leaves.
- The leaves have tiny, microscopic pores called stomata, which are the main sites for this water loss.
- Water evaporates through these stomata. Each stoma is surrounded by guard cells, which are specialized cells.
- These guard cells play a crucial role in regulating the rate of transpiration by opening and closing the stomata. This mechanism helps plants manage water loss in different environmental conditions. It is an essential part of the plant's water cycle.
In simple words: Transpiration is when plants release water vapor from their leaves into the air. This happens mostly through tiny holes called stomata, which are controlled by guard cells.

🎯 Exam Tip: When writing about transpiration, ensure you explain what it is, where it occurs (stomata), and how it's regulated (guard cells).

Question 2. Write the types of tropism.
Answer: Tropism refers to the growth movement of a plant part in a particular direction in response to an external stimulus. Based on the nature of the stimuli, tropism can be classified as follows:
- **Phototropism**: This is the movement of a plant part towards or away from light. For example, the shoot of a plant grows towards light (positive phototropism), while roots typically grow away from light (negative phototropism).
- **Geotropism**: This is the movement of a plant in response to gravity. Roots grow downwards into the soil (positive geotropism), while the shoot grows upwards, away from gravity (negative geotropism).
- **Hydrotropism**: This is the movement of a plant or a part of a plant towards water. For example, roots grow towards water (positive hydrotropism), which is essential for nutrient absorption.
- **Thigmotropism**: This is the movement of a plant part due to touch. Climbing vines, for instance, coil around a support when they touch it.
- **Chemotropism**: This is the movement of a plant part in response to chemicals. A common example is the growth of a pollen tube towards the ovule in response to sugars present on the stigma.
Generally, tropism is termed positive if growth is towards the signal and negative if it is away from the signal. This directional growth helps plants optimize their position for survival and resource acquisition.
In simple words: Tropism is how plants grow towards or away from things like light, gravity, water, touch, or chemicals. Shoots usually grow towards light and away from gravity, while roots grow towards gravity and water, and away from light.

🎯 Exam Tip: For each type of tropism, define the stimulus, explain the direction of movement (positive or negative), and provide a clear plant example.

VIII. Higher Order Thinking Skills :

Question 1. While conducting experiments to study the effects of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X however bends " away from stimulus A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to factors related with Earth. Keeping these points in mind, answer the following questions:
(a) What could be stimulus A ?
(b) Name the stimulus seen in B.
(c) What could be stimulus-C?
Answer:
(a) Stimulus A could be Water. Roots grow towards water (positive hydrotropism), and stems bend away from water (negative hydrotropism, though often less pronounced than other tropisms).
(b) The stimulus seen in B is Gravity. Roots grow towards gravity (positive geotropism), and it is related to factors of Earth.
(c) Stimulus C could be Light. Roots bend away from light (negative phototropism), and stems bend towards light (positive phototropism). This allows the plant to position itself optimally for growth.
In simple words: A is water (roots grow to it). B is gravity (roots grow down because of it). C is light (stems grow to it, roots grow away from it).

🎯 Exam Tip: When analyzing complex scenarios, break down each response (root and stem) to each stimulus individually, and recall whether the response is positive or negative.

Question 2. An organism A which cannot move from one place to another makes a simple food B from the substances C and D available in the environment. This food is made in the presence of green coloured substance E present in organs F in the presence of light energy in a process called G. Some of the simple food B also gets converted into a complex food H for storage purposes. This food gives blue-black colour with iodine solution?
(a) What is (i) organism A (ii) food B and food H?
(c) Name (1) green coloured substance E and organ F.
(d) What is the process G?
Answer:
(a) (i) Organism A refers to Green plants. They are stationary and produce their own food.
(ii) Food B is Glucose, the simple sugar made during photosynthesis. Food H is Starch, the complex form of sugar stored by plants, which turns blue-black with iodine.
(c) Green coloured substance E is Chlorophyll, the pigment that absorbs light energy. Organ F is Leaves, where photosynthesis mainly occurs.
(d) Process G is Photosynthesis, the overall process of making food from simple substances using light energy. This process is fundamental to life on Earth.
In simple words: Organism A is green plants. Food B is glucose, and food H is starch. E is chlorophyll, found in F, which are leaves. The process G is photosynthesis.

🎯 Exam Tip: This question tests your complete understanding of photosynthesis; ensure you can identify all reactants, products, key components (chlorophyll, leaves), and the main process itself.