RBSE Solutions Class 11 Biology Chapter 17 Root External Morphology

RBSE Class 11 Biology Chapter 17 Multiple Choice Objective Questions

Question 1. From which part of plant, root arises?
(a) Plumule
(b) Radicle
(c) Seed coat
(d) Seed embryo
Answer: (b) Radicle
In simple words: The radicle is the first part of a plant embryo that emerges from the seed during germination and develops into the primary root.

🎯 Exam Tip: Remember that the radicle is the embryonic root, while the plumule is the embryonic shoot, which develops into the stem and leaves.

Question 2. The root arises from other then radicle is called which root
(a) Tap root
(b) Fibrous root
(c) Lateral root
(d) Adventitious root
Answer: (d) Adventitious root
In simple words: Adventitious roots grow from parts of the plant other than the radicle, such as stems or leaves.

🎯 Exam Tip: Know the different types of root systems, including tap roots, fibrous roots, and adventitious roots, and how they form.

Question 4. The shape of root of carrot is
(a) Conical
(b) Tuberous
(c) Napiform
(d) Fusiform
Answer: (a) Conical
In simple words: A carrot root has a conical shape, meaning it is wide at the top and tapers downwards.

🎯 Exam Tip: Be familiar with common examples of root modifications and their characteristic shapes for storage, such as conical (carrot), fusiform (radish), and napiform (turnip).

Question 5. Lateral roots originate from
(a) Pericycle
(b) Epidermis
(c) Peribleme
(d) Xylem bundles
Answer: (a) Pericycle
In simple words: Lateral roots, which are side branches, begin to grow from a layer inside the root called the pericycle.

🎯 Exam Tip: Understand the internal structure of roots and the function of different tissues, especially the pericycle in initiating lateral root growth.

Question 6. Out of the following which plant part cannot be considered as root
(a) Radish
(b) Colocassia
(c) Sweet potato
(d) Dahelia
Answer: (b) Colocassia
In simple words: Colocassia (Arbi) is a corm, which is a modified stem, while radish, sweet potato, and dahlia have modified roots for storage.

🎯 Exam Tip: Distinguish between modified roots and modified stems that store food, as they often look similar but originate from different plant parts.

Question 7. In banyan tree, following is found
(a) Prop roots
(b) Stilt roots
(c) Mycorrhiza root
(d) Parasitic root
Answer: (a) Prop roots
In simple words: Banyan trees have prop roots that grow downwards from branches to provide extra support to the large tree.

🎯 Exam Tip: Learn the different types of aerial roots and their specific functions in various plants, such as prop roots for support in banyan trees.

Question 8. Hygroscopic roots are found in
(a) Mangroove trees
(b) Epiphytic roots
(c) Aquatic roots
(d) Xerophytes
Answer: (a) from nodes of stem
In simple words: Hygroscopic roots are found on epiphytes, which are plants that grow on other plants and absorb moisture from the air.

🎯 Exam Tip: Understand the adaptations of plants in different habitats; hygroscopic roots are a key feature for epiphytes to survive without direct soil contact.

Question 9. Parasitic roots are found in
(a) Maize
(b) Potato
(c) mistletoe
(d) Teak
Answer: (b) Epiphytic roots
In simple words: Parasitic roots, also known as haustoria, are found in plants like mistletoe that draw nutrients from a host plant.

🎯 Exam Tip: Be aware of various root modifications beyond basic functions, including parasitic roots which are specialized for nutrient absorption from other organisms.

Question 10. Parasitic roots are found in
(a) Maize
(b) Potato
(c) mistletoe
(d) Teak
Answer: (c) mistletoe
In simple words: Mistletoe uses special roots called haustoria to grow on other plants and take water and nutrients from them.

🎯 Exam Tip: Recall examples of plants with specialized roots, such as parasitic plants like mistletoe which use their roots to absorb resources from host plants.

RBSE Class 11 Biology Chapter 17 Very Short Answer Questions

Question 1. Respiratory roots are found in which plants?
Answer: Respiratory roots are found in plants that grow in marshy areas, such as Mangrove plants. These roots, called pneumatophores, grow upwards from the soil to help the plant get oxygen.
In simple words: Plants in muddy, watery places like mangroves have roots that grow up into the air to breathe.

🎯 Exam Tip: Remember pneumatophores are a unique adaptation for plants in oxygen-poor, waterlogged soils.

Question 2. Hygroscopic root are found in epiphytic roots?
Answer: Yes, hygroscopic roots are found in epiphytic plants. These roots are also called aerial absorbing roots. They are specialized to absorb moisture directly from the atmosphere, helping epiphytes survive without soil.
In simple words: Epiphytic plants, which grow on other plants, have special roots that can take water right out of the air.

🎯 Exam Tip: Focus on the "hygroscopic" characteristic, which means "water-absorbing," and its importance for epiphytic plant survival.

Question 3. What are the function of Root cap/calyptra?
Answer: The root cap, also known as calyptra, has several functions:
• It protects the root meristem, which is the growing tip of the root, as it pushes through the soil.
• It secretes mucilage, a slimy substance that lubricates the root tip, making it easier to penetrate hard soil.
• It helps the root sense gravity, guiding its growth downwards.
• It helps in balancing the root structure.
In simple words: The root cap acts like a protective helmet for the root's growing tip, helping it push through soil, sensing down, and staying balanced.

🎯 Exam Tip: Highlight the protective and navigational roles of the root cap for full marks.

RBSE Class 11 Biology Chapter 17 Short Answer Questions

Question 1. How many types of root are there? Write the names of them.
Answer: Roots are mainly of two types based on how they originate: tap roots and adventitious roots.
(a) Tap root: This root system develops from the radicle of a seed. The radicle grows into a main primary root, which then produces smaller lateral roots (secondary and tertiary roots). This system is typical in dicot plants.
(b) Adventitious root: These roots grow from any part of the plant other than the radicle, like stems or leaves. In monocot plants, the tap root is short-lived and is replaced by adventitious roots. Adventitious roots can be of three types based on their origin:
• Fibrous roots: These are a cluster of similar, thread-like roots that grow from the base of the stem (e.g., rice, wheat, maize) or from nodes of horizontal stems (e.g., grass).
• Foliar roots: These roots grow from the petiole or veins of a leaf, often due to injury. Examples include Pogostemon and Bryophyllum.
• True adventitious roots: These roots grow from the nodes and internodes of the stem, such as the prop roots of banyan trees and stilt roots.
In simple words: There are two main kinds of roots: tap roots, which grow straight down from the seed, and adventitious roots, which can grow from other parts of the plant like the stem or leaves. Adventitious roots can be thin and spread out (fibrous), grow from leaves (foliar), or grow directly from the stem (true adventitious roots).

🎯 Exam Tip: Clearly define tap and adventitious roots based on their origin and give relevant examples for each type and subtype.

Question 2. What are the function of root?
Answer: Roots perform two main kinds of functions: primary and secondary.
(A) Primary functions of roots: These are essential for all roots.
1. Anchorage: Roots firmly fix the plant to the soil, providing strong mechanical support to the plant's upper parts.
2. Absorption: Roots absorb water and minerals from the soil. This is a very important function for most land plants.
3. Conduction of water and minerals: Roots move the absorbed water and minerals upwards to other parts of the plant. Root pressure plays a role in this movement.
4. Translocation of organic nutrients: Roots are not green and cannot make food. Sugar made in the leaves through photosynthesis is transported downwards to the root tissues, where it is used.
(B) Secondary functions of roots: These are specialized functions performed by modified roots.
1. Food storage: Many fleshy roots store food materials. Examples include carrot, radish, sweet potato, and turnip.
2. Additional mechanical support: Some roots are modified to give extra support to the plant. Examples are prop roots (banyan), stilt roots (maize, sugarcane), and buttress roots.
3. Symbiotic nitrogen fixation: In leguminous plants, roots have nodules with bacteria that fix atmospheric nitrogen, making it usable for the plant.
4. Floating and balancing: Some aquatic plant roots store air, helping the plant float and stay balanced (e.g., Jussiaea).
5. Hygroscopic roots: Aerial roots in epiphytic plants (e.g., orchids) absorb moisture from the air.
6. Reproduction: Some modified roots have buds that can grow into new plants, helping with vegetative propagation (e.g., sweet potato).
7. Climbing: Weak-stemmed plants develop climbing roots that help them attach to supports (e.g., money plant).
In simple words: Roots mainly hold the plant in the ground and soak up water and food from the soil. They also help move water up the plant. Some roots have special jobs like storing food, giving extra support, helping plants float, absorbing air moisture, or helping new plants grow.

🎯 Exam Tip: Organize your answer by primary and secondary functions, providing a brief explanation and one clear example for each secondary function.

Question 3. Differentiate between Tap root and adventitious roots?
Answer:

🎯 Exam Tip: For differentiation questions, use a table format to clearly show contrasting points between the two types of roots.

RBSE Class 11 Biology Chapter 17 Essay Type Questions

Question 1. Write in detail how the roots are modified as mechanical tissue with help of well labelled diagram?
Answer: Roots are modified to provide mechanical support to plants, especially in specific environmental conditions. These modifications act as mechanical tissues.
1. Prop Roots: In large tropical trees like the banyan (Ficus benghalensis), horizontal branches produce aerial roots. These roots grow vertically downwards from the branches, much like hanging strings. Once they reach the soil and anchor, they thicken, becoming strong pillars. These prop roots support the heavy horizontal branches, and over time, they can even replace the main trunk if it dies. For example, the great banyan tree in the Indian Botanical Garden is supported by hundreds of prop roots.
2. Stilt Roots: These roots are found in shrubs and small trees that grow in unstable soils, such as screw-pine (Pandanus foetidus) found near marshes. Short roots grow obliquely downwards from the base of the stem, acting like stilts. They provide additional support and anchorage. Stilt roots are also seen in maize plants, growing from the lower nodes of the stem, and in mangrove plants like Rhizophora.
3. Root Buttresses: In some very large trees, instead of thin stilt roots, broad plank-like roots radiate from the tree's base, resembling wings. These buttresses are partly root and partly stem. They help stabilize very tall and heavy trees against strong winds, for example, in old Bombax ceiba and Ficus species.
4. Climbing Roots: Certain climbing plants develop adventitious roots from their nodes that help them climb up supports. These roots wrap around and cling to the support, like hands holding on. Examples include the betel vine and Scindapsus officinalis.
5. Clinging Roots: Epiphytes, like orchids, have special clinging roots that help them attach to the surfaces of other plants or tree bark. These roots enter small cracks and provide firm anchorage, even though their primary role is not absorption.
6. Haptera or Holdfasts: In plants like Podostemaceae or some algae, the main plant body is thalloid (flat and undifferentiated). Special root processes, called holdfasts or haptera, stick the plant firmly to rocks. Adhesive discs of climbers like Ficus repens also act as holdfasts, flattening to stick to their supports.
7. Contractile or Pull Roots: Plants with underground stems (like rhizomes, bulbs, tubers) have contractile roots. These roots can shorten or swell, pulling the aerial shoot or underground parts deeper into the soil. This keeps the plant at a proper level and protects it from environmental changes. Examples include Canna, Crocus, and Lilium.
8. Floating Roots: Aquatic plants like Jussiaea repens have specialized floating roots that grow from their nodes. These roots are spongy and filled with air, providing buoyancy to keep the plant afloat. They dry out quickly if removed from water and also aid in aerating the submerged parts of the plant.
9. Root - Thorns: In some palms (like Acanthorhiza) and aroids, adventitious roots from the stem's base become hard, pointed, and thorn-like. These root-thorns help protect the plants from grazing animals.
In simple words: Roots can change their shape and structure to help plants in many ways. Some grow like pillars (prop roots) or stilts to hold up heavy plants. Others spread out like planks (buttresses) at the base of big trees. Some roots help plants climb (climbing roots) or stick to surfaces (clinging roots and holdfasts). There are also roots that pull the plant deeper into the soil (contractile roots) or help it float (floating roots), and even some that become sharp like thorns to protect the plant.

🎯 Exam Tip: When describing root modifications, always state the function clearly and provide a specific plant example for each type.

Question 2. How tap root and adventitious roots are modified for storage function with help of well labelled diagram?
Answer: Both tap roots and adventitious roots can be modified to store food materials. These storage roots become swollen and take on various shapes.
Modifications for Storage in Tap Roots:
In some plants, the primary tap root becomes thick and fleshy to store food. The smaller secondary roots usually remain thin and continue to absorb water and minerals. These storage tap roots often have distinct shapes:
• Conical: These roots are broad at the top and gradually taper downwards, forming a cone shape. Example: Carrot.
• Fusiform: These roots are swollen in the middle and narrow towards both the base and the apex, giving them a spindle shape. Example: Radish.
• Napiform: These roots are almost spherical or globular at the base and suddenly taper towards the apex, giving them a top-like shape. Example: Turnip and Beet.
• Tuberous: These are storage roots that do not have a definite shape. Example: Mirabilis jalapa (4 O'clock plant).
• Nodulated: These roots have small swellings (nodules) at their tips due to the accumulation of stored food. Example: Ginger.
Modifications of Adventitious Roots for Storage:
Some adventitious roots also store food, becoming swollen. They can grow singly or in clusters:
• Tuberous roots: These are adventitious roots that store food and swell up, but they do not have a fixed shape and grow individually. Example: Sweet potato (Ipomoea batata). These roots can also have adventitious buds, making them reproductive roots.
• Fasciculated roots: These are tuberous adventitious roots that grow in clusters at the base of the stem. Examples: Dahlia and Asparagus. In asparagus, these fleshy roots appear at regular intervals on the normal roots.
• Annulated roots: These thickened roots appear as if they are made of a series of discs stacked one on top of another. Example: Ipecac (Psychotria ipecacuanha).
In simple words: Both main roots (tap roots) and roots growing from stems or leaves (adventitious roots) can get big and fat to store food. Tap roots can be shaped like cones (carrot), spindles (radish), or tops (turnip). Adventitious roots can be single, shapeless big roots (sweet potato), or they can grow in bunches (dahlia), or look like stacked rings (ipecac).

🎯 Exam Tip: Clearly distinguish between tap root and adventitious root modifications, providing specific shapes and plant examples for each category.

Question 3. Explain the different zones of root apex with help of well labelled diagram?
Answer: A typical root apex, the tip of a root, can be divided into several distinct regions or zones, starting from the very end.
1. Root Cap Zone:
This is the outermost protective layer at the very tip of the root.
Function:
• It shields the delicate root meristem from damage as the root grows through abrasive soil particles.
• It secretes mucilage, a slimy substance that helps lubricate the root tip, making it easier for the root to penetrate the soil.
• It plays a role in perceiving gravity, helping the root grow downwards (geotropism).
2. Growing point or Meristematic Zone (Zone of Cell Division):
Located just behind the root cap, this zone is typically 0.25 - 1.0 mm long.
• It consists of rapidly dividing cells (meristematic cells) that are responsible for the growth in length of the root.
• The shape of this zone resembles an inverted concave dome.
• In its center is a region called the quiescent center, where cells divide less frequently but are vital for root regeneration.
Function:
• This zone continuously produces new cells, adding them to both the root cap and the region behind it, contributing to root elongation.
3. Zone of Elongation:
This zone is found immediately above the meristematic zone and is usually 1 - 10 mm long.
• Cells in this region do not divide but rapidly increase in size, especially in length.
• This elongation of cells is the primary factor responsible for pushing the root tip deeper into the soil.
• The external cells in this zone are capable of absorbing water and minerals from the soil.
4. Root Hair Zone or Zone of Differentiation (Zone of Maturation):
Located above the zone of elongation, this region is typically 1 - 6 cm long.
• In this zone, cells mature and differentiate into specialized tissues like epiblema (root epidermis), cortex, endodermis, pericycle, xylem, and phloem.
• Many epiblema cells elongate outwards to form unicellular root hairs.
• As the root grows, new root hairs develop closer to the tip, while older ones further up shrivel and die off.
Function:
• Root hairs significantly increase the surface area of the root, which greatly enhances the absorption of water and minerals from the soil.
• Radial differentiation of tissues in this zone leads to the formation of vascular bundles, allowing for transport.
In simple words: The root tip has different parts. The root cap is like a shield at the very end. Behind it is the growing part (meristematic zone) where new cells are made. Above that, the cells stretch out and make the root longer (zone of elongation). Finally, in the root hair zone, cells become special, and tiny hairs grow to soak up water and nutrients.

🎯 Exam Tip: Clearly label and describe each zone of the root apex, emphasizing its distinct cellular activity and primary function for thorough understanding.