RBSE Solutions Class 11 Biology Chapter 19 Leaf External Morphology

RBSE Class 11 Biology Chapter 19 Multiple Choice Objective Questions

Question 1. Leaf Blade or lamina modified in peas
(a) Thoms
(b) scales
(c) Tendrils
(d) Stem
Answer: (c) Tendrils
In simple words: In peas, the flat part of the leaf, called the lamina or blade, changes shape to become thin, coiling tendrils. These tendrils help the pea plant climb.

🎯 Exam Tip: Remember specific plant examples for leaf modifications, as they are commonly tested. Peas are a classic example of tendrils for support.

Question 2. Swollen leaf base is called
(a) Pulvinus
(b) Sheathing
(c) Auriculate
(d) Pinnate
Answer: (a) Pulvinus
In simple words: The base of a leaf can sometimes be swollen, and this swollen part is known as a pulvinus. It helps in leaf movements in some plants.

🎯 Exam Tip: Know the different parts of a leaf and the specific terms used for any modifications, like the pulvinus for a swollen leaf base.

Question 4. In Pitcher plant, pitcher is modified of which part of leaf?
(a) Leaf apex
(b) Leaf Lamina
(c) petiole
(d) axis
Answer: (b) Leaf Lamina
In simple words: For a Pitcher plant, the pitcher part, which catches insects, is actually a changed form of the flat, main part of the leaf, called the lamina.

🎯 Exam Tip: Be aware that insectivorous plants show interesting leaf modifications. For Pitcher plants, specifically, the lamina forms the pitcher. For others, it might be different parts.

Question 5. Phyllode is modification of-
(a) Petiole
(b) Leaf Base
(c) leaf apex
(d) stem
Answer: (a) Petiole
In simple words: A phyllode is when the stalk of a leaf, called the petiole, becomes flat and green, acting like a leaf blade. This helps reduce water loss.

🎯 Exam Tip: Phyllodes are an adaptation to dry conditions. Know that the petiole, not the lamina, is the part that gets modified into a leaf-like structure.

Question 6. Multipinnate compound or decompound leaf is an example of-
(a) Neem
(b)Babool
(c) Tamarind
(d) carrot
Answer: (d) carrot
In simple words: A carrot plant has leaves that are divided many times, making them very complex and fern-like. This kind of leaf is called multipinnate or decompound.

🎯 Exam Tip: Understand the differences between simple, pinnately compound, and palmately compound leaves, and specific examples for each type. Multipinnate refers to leaves that are repeatedly divided.

Question 7. Leaflet tendril is an example of –
(a) Pea
(b) Cauliflower
(c) Carrot
(d) Potato
Answer: (a) Pea
In simple words: In pea plants, some of the small leaf parts, called leaflets, change into thin, coiling structures known as tendrils. These tendrils help the plant climb up for support.

🎯 Exam Tip: Differentiate between different types of tendrils, such as whole leaf tendrils, leaf tip tendrils, petiole tendrils, and leaflet tendrils, and know which plants exhibit them.

Question 8. Al
(a) In hydrophytes
Answer: (a) In hydrophytes
In simple words: Without the full question, it is hard to be precise, but if "Al" refers to adaptations or a specific feature of Alisma or other aquatic plants, it would relate to hydrophytes. Hydrophytes are plants that grow in water.

🎯 Exam Tip: Pay attention to the full context of questions, especially when they appear incomplete. Hydrophytes have unique adaptations for living in water, such as floating leaves or reduced root systems.

RBSE Class 11 Biology Chapter 19 Very Short Answer Type Questions

Question 1. Reticulate venation is found in which plants?
Answer: Reticulate venation is a pattern where leaf veins form a net-like structure. This type of venation is a special feature of dicotyledons, such as Peepal (Ficus religiosa) and Hibiscus.
In simple words: Plants like Peepal and Hibiscus have veins in their leaves that look like a tiny net. This is called reticulate venation and is common in plants with two seed leaves.

🎯 Exam Tip: When asked about venation, remember to name both the type and provide specific plant examples, highlighting key features like dicotyledons or monocotyledons.

Question 2. Swollen spongy petiole is found in?
Answer: A swollen and spongy petiole (leaf stalk) is found in plants like Nasturtium, also known as Jal kumbhee. This modification often helps aquatic plants to float.
In simple words: The swollen, soft leaf stalk of plants like Nasturtium (Jal kumbhee) helps them float on water.

🎯 Exam Tip: Relate leaf modifications to their functions. Swollen petioles often indicate an adaptation for buoyancy in aquatic environments.

Question 3. Which part of the plant, food storage part of onion is?
Answer: The food storage part of an onion is primarily its fleshy scale leaves, which are actually modified leaf bases. These leaves develop from a very short, flattened stem (the basal plate of the onion).
In simple words: The onion stores food in its thick, juicy leaves, which grow from a tiny stem at its bottom. These leaves are like special storage leaves.

🎯 Exam Tip: For questions on plant parts, specify the exact modification. In onions, it's the fleshy scale leaves (modified leaf bases) that store food, supported by a reduced stem.

Question 4. Explain different parts of leaf with help of well labelled diagram?
Answer: The main parts of a leaf are the leaf base, the petiole, and the leaf blade (lamina). The leaf base connects the leaf to the stem and often has small, leaf-like structures called stipules. The petiole is the stalk that holds the leaf blade away from the stem, allowing it to catch sunlight and air. The leaf blade is the broad, flat green part where most photosynthesis happens. It has veins that transport water and nutrients.

In simple words: A leaf has three main parts: the base (which attaches to the stem, sometimes with small leaves called stipules), the stalk (called the petiole), and the wide, flat part (called the lamina or blade) where it makes food using sunlight.

🎯 Exam Tip: Clearly label all three main parts of a leaf: lamina (blade), petiole, and leaf base. Also, mention accessory structures like stipules if present and their typical functions.

RBSE Class 11 Biology Chapter 19 Short Answer Type Questions

Question 1. Differentiate between Stem branch and Compound leaf?
Answer: Here is a table differentiating between a stem branch and a compound leaf:

In simple words: A stem branch is a full part of the plant with leaves growing on it, while a compound leaf is a single leaf made of many smaller parts called leaflets. The key difference is where buds appear and how the parts are arranged.

🎯 Exam Tip: When differentiating, use a clear table format. Focus on key distinguishing features like the presence/absence of axillary buds and the developmental origin of the structures.

Question 2. Write about different types of leaf?
Answer: A typical leaf consists of three main parts that are usually well-defined:
1. The leaf base: This is the part that attaches the leaf to the stem. It is often provided with a pair of small, leaf-like outgrowths called stipules.
2. The petiole: This is the stalk of the leaf. It connects the leaf blade to the stem and holds it in a position to get enough sunlight.
3. The leaf blade or lamina: This is the broad, flat, green part of the leaf. It is the primary site for photosynthesis. It contains veins and veinlets that form patterns to support the leaf and transport materials.
In simple words: A leaf has three main parts: the base (connecting to the stem), the petiole (the stalk), and the lamina (the flat, green part). Sometimes, there are small stipules near the base.

🎯 Exam Tip: When describing leaf parts, provide a brief function for each. Also, ensure you use the correct terminology (leaf base, petiole, lamina) for full marks.

Question 3. What is heterophylly? Explain it with help of well labeled diagram?
Answer: Heterophylly is when a single plant produces more than one shape of leaves. This phenomenon is common in certain amphibious plants, like Limnophila heterophylla. It serves as an adaptive advantage for the plant, allowing it to survive in different environments, such as submerged and aerial conditions. For example, a plant might have finely divided leaves underwater and broad, undivided leaves in the air to better suit each environment.
In simple words: Heterophylly means one plant grows different shapes of leaves. This helps the plant live in various conditions, like having different leaves for water and air.

🎯 Exam Tip: Define heterophylly clearly and provide an example. Emphasize that it is an adaptive feature, and if a diagram is requested, ensure it clearly shows the different leaf forms on the same plant.

Question 4. Differentiate between Opposite decussate and opposite superposed?
Answer: Both opposite decussate and opposite superposed are types of opposite phyllotaxy, where a pair of leaves arises at each node on opposite sides of the stem.
- In opposite superposed phyllotaxy, all pairs of leaves on a branch grow in the same plane. This means only two vertical rows of leaves are formed, as seen in plants like Jamun and Guava.
- In opposite decussate phyllotaxy, each pair of leaves at a node grows at a right angle to the pair immediately above or below it. This arrangement creates four vertical rows of leaves on the stem, as found in plants like Calotropis, Zinnia, and Tulsi.
In simple words: In opposite superposed leaves, all leaf pairs align vertically. In opposite decussate leaves, each pair turns 90 degrees from the one above or below it, making four vertical lines of leaves.

🎯 Exam Tip: Clearly state that both are forms of opposite phyllotaxy. The key to differentiating them lies in the orientation of successive leaf pairs: same plane for superposed, right angles for decussate.

Question 5. Differentiate between Free lateral stipules and Adnate Stipules.
Answer: Stipules are small, leaf-like outgrowths at the base of the petiole. They can be classified into different types:
1. Free lateral stipules: These are two small, green stipules found on both sides of the leaf base. They are completely separate from the petiole. Examples include Hibiscus rosa sinensis and Gossypium.
2. Adnate stipules: These are two lateral stipules that are fused (attached) to the petiole for some distance. However, their front part remains free. Examples include Rose, groundnut, and Lupin.
In simple words: Free lateral stipules are separate from the leaf stalk, like in Hibiscus. Adnate stipules are partly joined to the leaf stalk, as seen in roses.

🎯 Exam Tip: When differentiating stipule types, highlight whether they are attached to the petiole or completely free, and always include characteristic plant examples.

RBSE Class 11 Biology Chapter 19 Long Answer Type Questions

Question 1. Explain various modifications of Petiole with help of well labelled diagram?
Answer: The petiole, also known as the leaf stalk or mesopodium, is a cylindrical or slightly cylindrical structure that connects the leaf blade (lamina) to the stem. Its main role is to hold the lamina up to sufficient light and air for photosynthesis. Leaves with petioles are called petiolate (e.g., Peepal, mango, guava, Hibiscus), while those without are sessile (e.g., wheat, rice).
Petioles can be modified in several ways to perform additional functions:
1. Winged petiole: In this modification, the petiole becomes flattened and leaf-like, enabling it to perform photosynthesis, similar to a leaf blade. This is often found in compound leaves, such as those of Citrus and orange.
2. Phyllode: Here, the lamina of some compound leaves falls off early, and the petiole changes into a flat, green, leaf-like structure to synthesize food. Phyllodes usually grow vertically to minimize sunlight exposure, which helps reduce transpiration. Australian acacia and Parkinsonia are examples.
3. Tendrillar petiole: In some plants with weak stems, the petioles are modified into tendrils. These coiling structures help the plant climb for support, as seen in Clematis and Nepenthes.

In simple words: The leaf stalk, called the petiole, can change in different ways. It can become flat and leaf-like (winged petiole), or turn into a flat green structure when the leaf blade falls off (phyllode), or even become a coiling tendril to help the plant climb.

🎯 Exam Tip: Clearly define the petiole and then list each modification with its specific characteristics and a plant example. Ensure your diagram clearly illustrates each modified type of petiole.

Question 2. What is venation? Explain different types of venation?
Answer: Venation refers to the specific arrangement or pattern of veins and veinlets within the lamina (leaf blade) of a leaf. These veins contain vascular tissues (xylem and phloem) that transport water, minerals, and prepared food throughout the leaf. They also provide structural support to the leaf blade.
There are two main types of venation:
1. Reticulate venation: In this type, the veinlets are irregularly distributed, forming a complex network. This pattern is characteristic of dicotyledonous plants, such as Peepal (Ficus religiosa) and Hibiscus.
(a) Unicostate (Pinnate reticulate): There is a single main vein (midrib) from which lateral branches arise and form a network. Examples: Peepal, Mango.
(b) Multicostate (Palmate reticulate): Several main veins of similar thickness arise from the leaf base and branch out to form a network.
(i) Convergent: Main veins converge towards the apex of the lamina. Examples: Smilax, Zizyphus, Nux vomica.
(ii) Divergent: Main veins diverge towards the margins of the lamina. Examples: Papaya, Cucurbita, Grape vine.
2. Parallel venation: In this type, the veins run parallel to each other and do not form a network. This pattern is characteristic of monocotyledonous plants.
(a) Unicostate (Pinnate parallel): A single main vein runs from the leaf base, with numerous lateral veins running parallel to it towards the margin. Examples: Banana, Canna.
(b) Multicostate (Palmate parallel): Several main veins run parallel to each other.
(i) Convergent: Main veins run parallel and converge at the apex of the lamina. Examples: Maize, Sugarcane, Wheat, Bamboos, Grasses.
(ii) Divergent: Main veins spread out towards the margins of the lamina. Example: Fan palm (Borassus flabellifer).

In simple words: Venation is how veins are arranged in a leaf. There are two main kinds: reticulate, where veins form a net (like in mango leaves), and parallel, where veins run side-by-side (like in grass). Each kind has unicostate (one main vein) and multicostate (many main veins) sub-types.

🎯 Exam Tip: When explaining venation, always start with a clear definition, then describe the two main types (reticulate and parallel), including their sub-types and characteristic plant examples. A simple diagram is excellent for illustrating the patterns.

Question 3. Difference between simple leaf and compound leaf? Explain different types of compound leaf with help of well labelled diagram?
Answer:
**Difference between Simple Leaf and Compound Leaf:**

**Types of Compound Leaves:**
Compound leaves are characterized by the lamina being divided into distinct units called leaflets, which are attached to a common axis (rachis) or petiole.
**1. Pinnate Compound Leaves:** In these leaves, leaflets are arranged along a common axis called the rachis, which is an extension of the petiole.
- **Unipinnate:** The leaflets are directly attached to the main rachis.
- **Paripinnate:** Even number of leaflets, borne in pairs, with no terminal leaflet. Examples: Tamarindus indica, Cassia.
- **Imparipinnate:** Odd number of leaflets, with a single unpaired leaflet at the apex of the rachis. Examples: Neem, Rose.
- **Bipinnate:** The main rachis divides into secondary rachises (rachillae), and leaflets are borne on these secondary rachillae. Example: Acacia nilotica.
- **Tripinnate:** The secondary rachis further divides into tertiary rachises, with leaflets borne on them. The leaf is thrice pinnate. Example: Moringa (Sahijan).
**2. Palmate Compound Leaves:** In these leaves, all leaflets radiate from a single point at the tip of the petiole, like fingers from the palm of a hand.
- **Unifoliate:** Only one leaflet is present, appearing as a simple leaf, but it is articulated to the petiole. Example: Citrus.
- **Bifoliate:** Two leaflets arise from the tip of the petiole. Example: Balanites roxburghii.
- **Trifoliate:** Three leaflets arise from the tip of the petiole. Example: Oxalis, Clover.
- **Quadrifoliate:** Four leaflets arise from the tip of the petiole. Example: Paris quadrifolia.
- **Multifoliate:** Five or more leaflets arise from the tip of the petiole. Example: Bombax malabarica.

In simple words: A simple leaf has one whole blade, even if it's cut, while a compound leaf has many small leaf parts called leaflets. Compound leaves can be pinnate (leaflets along a central stem) or palmate (leaflets spread out from one point like fingers).

🎯 Exam Tip: When differentiating, clearly state the key difference: whether the lamina is completely divided or not. For types of compound leaves, describe both pinnate and palmate forms, including their sub-types, and use accurate diagrams to illustrate. Always mention the presence or absence of axillary buds as a key distinguishing feature.

Answer:
2. Palmate Compound Leaves: In these leaves, the leaflets spread out like fingers from a single point on a very short main stalk (rachis). These leaflets might have a small stem (petiolate) or be directly attached (sessile). These types of leaves include:
1. Unifoliate: Here, a palmate compound leaf has only one leaflet, which is attached at the top of the petiole. Examples are Citrus (Khatta) and Lemon.
2. Bifoliate: This leaf type has two leaflets growing next to each other at the end of the petiole. Examples are Balanites roxburghii and Hardwickia binnata.
3. Trifoliate: These leaves have three leaflets attached at the very end of the petiole. Examples include Aegle marmelos (wood apple), Oxalis corniculata, and Trifolium (Clover). These are different from other three-leaflet compound leaves because all three leaflets join at the tip of the petiole.
4. Quadrifoliate: This leaf has four leaflets joined at the tip of its petiole, like in Paris quadrifolia.
5. Multifoliate: A palmately compound leaf with five or more terminal leaflets, arranged like fingers spreading from a palm. Examples are Bombax malabarica and Cleome viscosa. In simple words: In palm-shaped compound leaves, all the small leaf parts grow from one point at the end of the main stem, like fingers. These can have one, two, three, four, or many leaflets depending on the plant.

🎯 Exam Tip: Remember the key difference for palmately compound leaves: all leaflets connect at a single point, resembling fingers on a palm, unlike pinnate leaves where leaflets connect along a central axis.

Question 4. Explain in detail various functions of leaf?
Answer: Leaves perform several important functions for a plant:
(A) Primary functions:
1. Photosynthesis: Green leaves are the main site where plants make their food using sunlight, water, and carbon dioxide. This process is called photosynthesis.
2. Gaseous exchange: Leaves have tiny pores called stomata on their surface, guarded by two kidney-shaped cells. These stomata allow gases like carbon dioxide and oxygen to move in and out, which is necessary for photosynthesis and respiration.
3. Transpiration: Plants lose water vapor mainly through the stomata and the surface of their leaves. This process, called transpiration, helps keep the plant cool and aids in moving water up from the roots.
4. Protection of bud: Leaves protect the young buds at the tips and sides of branches from drying out and physical damage.
5. Conduction: The veins and leaf stalks (petioles) of leaves contain tubes (vascular bundles) that transport food made in the leaves to other parts of the plant (phloem) and carry water and minerals from the roots to the leaves (xylem).
(B) Secondary functions:
1. Storage: Some desert plants (like Aloe, Agave) have thick, juicy leaves that store water, sticky substances, and food to survive dry periods. Onion bulbs store food in their fleshy leaf bases. Aquatic plants (like Eichhornia) have leaves that store air, helping them float. Some epiphytic plants (like Dischidia) have leaves modified into pitchers to collect rainwater.
2. Protection: In some plants (like Barberry, Opuntia), leaves or parts of them turn into sharp spines to protect the plant from animals grazing on them. In some dry-habitat plants, leaves are very small or modified into phyllodes to reduce water loss and protect the plant.
3. Support: In some climbing plants, parts of the leaf change into thin, coiled structures called tendrils, which help the plant climb onto other objects for support.
4. Nitrogen nutrition: Leaves of some insect-eating plants are modified into various types of traps. For example, Nepenthes and Sarracenia have leaves shaped like pitchers to catch insects. Utricularia has sac-like traps called bladders. These plants digest the trapped insects to get the nitrogen they need. In simple words: Leaves mainly make food for the plant using sunlight, breathe, and release water. They also help store food and water, protect the plant from harm, help it climb, and even catch insects for food.

🎯 Exam Tip: When explaining functions, categorize them into primary (essential for life) and secondary (special adaptations) to show a comprehensive understanding.

Question 5. Explain the modifications of leaf in insectivorous plants?
Answer: Leaves can change their shape and structure to perform special functions. Here are some modifications:
1. Storage Leaves: Some plants in salty or dry places, or members of the Crassulaceae family, have thick or swollen leaves. These juicy leaves store water, sticky substances, or food, helping the plant survive dry conditions. Examples include Aloe, Agave, Bryophyllum, and Sedum.
2. Leaf Tendrils: In some plants, the whole leaf or part of it changes into a tendril. Tendrils are long, thin, flexible, and coiled climbing parts that are very sensitive to touch and wrap around supports. Leaf tendrils can be of different types:
• Whole leaf tendrils: The entire leaf changes into a tendril, like in Lathyrus aphaca (wild pea). The small leaf-like parts (stipules) become larger to perform the job of normal leaves.
• Leaf tip tendril: The tips of the leaves become long and change into tendrils, as seen in Gloriosa superba (Glory Lily).
• Leaflet tendrils: In plants like Pisum sativum (pea) and Lathyrus odoratus (sweet pea), the upper few leaflets of the compound leaves change into tendrils.
• Petiole tendrils: In some plants, the leaf stalks (petioles) become long and change into tendrils, helping the plant climb. Examples are Clematis and Garden Nasturtium.
• Rachis tendril: In some plants, the tip of the main leaf stalk (rachis) or the whole rachis changes into a tendril.
3. Leaf Spines: In some plants, leaves or parts of them change into spines. These spines protect the plants from grazing animals and also help reduce water loss in dry environments. Leaf spines can be:
• In Barberry, the leaves on the main stem become spines.
• In Opuntia, the leaves from the buds in the leaf axils become spines.
• In Phoenix and Yucca, the tips of the leaves become spines.
• In Argemone, the edges of the leaf blade become spines.
• In Ulex, the leaves become spines, and the branches in their axils turn into thorns.
4. Leaf Hooks: Some plants have leaves modified into hook-like structures that help them climb. For example, in Bignonia unguis-cati, the three end leaflets of the compound leaf turn into stiff, claw-like hooks (like a cat's nails). These hooks firmly grip supports, helping the plant climb.
5. Phyllodes: Phyllodes are flat, green, leaf-like changes of petioles (leaf stalks) or rachis. The actual leaflets or leaf blades are very small or fall off early. Phyllodes perform photosynthesis and other leaf functions. They are an adaptation for dry conditions to reduce water loss. Examples include Australian Acacia and Parkinsonia. In Parkinsonia, the leaves are doubly compound, and the first main stalk is short and becomes a spine. The secondary stalks turn into phyllodes. In Australian Acacia, phyllodes hang downwards and have few stomata to reduce water loss.
6. Insect-catching leaves: In some insect-eating plants, leaves or parts of them are modified into special organs to catch insects. They digest these insects and absorb nitrogen to meet their needs. Some examples are:
1. Pitchers: In Nepenthes and Sarracenia, leaves are modified into pitcher-shaped traps to catch and digest insects. In Nepenthes, the pitcher itself is the modified leaf blade, and the leaf tip becomes a lid.
7. Pitcher of epiphytic plant: In the epiphytic climber Dischidia rafflesiana, the whole leaf becomes a pitcher with an opening at the base. These pitchers collect rainwater and debris, which are then absorbed by special roots called adventitious or nest roots.
8. Cataphylls (or scale leaves): These leaves are either dry and thin like paper or fleshy. They do not perform photosynthesis and mainly protect the plant.
9. Floral leaves: Floral parts such as sepals, petals, stamens, and carpels are all modified leaves. Sepals and petals look like leaves and protect the flower, but are not essential for reproduction. Petals are often colorful to attract insects for pollination. Stamens are modified leaves that bear pollen (microsporophylls), and carpels are modified leaves that bear ovules (megasporophylls). Both stamens and carpels are essential reproductive parts. In simple words: Leaves can change their shape for many reasons. They can store food or water, turn into climbing tendrils, become sharp spines for protection, form hooks to climb, flatten into phyllodes to reduce water loss, or even become traps to catch insects for nutrients. Some leaves also form the parts of a flower.

🎯 Exam Tip: When asked about leaf modifications, remember to classify them by function (storage, support, protection, nutrition) and provide specific plant examples for each.