Class 11 Biology Chapter 5 Questions & Answers

Important Questions Class 11 Biology Chapter 5: Morphology of Flowering Plants

Biology is an interesting subject. It involves the study of different forms of life, their classification, origin, and features and helps develop better awareness and understanding of life around us. It also prepares us for taking up a career in life sciences in our later life.

Chapter 5 of CBSE Class 11 Biology is about the morphology of flowering plants. Some of the key things that we will learn in this chapter include the root, the stem, the leaf, the inflorescence, the flower, the fruit, and the seed. We will also study the semi-technical description of a typical flowering plant as well as the description of some important flowering plant families. The chapter is exciting and very informative. Students must read and practise questions thoroughly from this chapter to score full marks in exams.

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Class 11 Biology Chapter 5 Important Questions with Solutions

Our subject matter experts believe that students should practise questions to write concise and better answers quickly without getting stressed. For this purpose, they have prepared Chapter 5 and Class 11 Biology Important Questions. They have collated these questions from NCERT textbooks, CBSE sample papers, Exemplar guides, and from the reference books. Apart from that, they have written the answers following the CBSE guidelines and exam pattern. The Important Questions from Class 11 Biology Chapter 5 include all the possible questions from this chapter.

Below are some of the questions and their answers from our question bank. Students can register on the Extramarks website to get full access to our Important Questions for Class 11 Biology Chapter 5.

Q1. Describe the various functions of the root system.

Answer 1:

Root systems help in maintaining the proper balance of water. The major functions of the root system are described as follows:

(a) Water absorption and minerals from the soil via diffusion.

(b) To provide proper anchorage to the plant parts.

(c) To store reserve food material

(d) Synthesise and generate the plant growth regulators.

Q2. Write a short note on different types of root systems.

Answer 2:

(a) In most dicotyledonous plants, direct elongation of the radicle occurs, leading to the formation of primary roots. This primary root grows inside the soil. Further, The primary roots and their branches constitute the taproot system, for example-mustard plants.

(b) In most monocotyledonous plants, the primary root is short-lived and is mostly replaced by many roots. Further, the primary roots originate from the base of the stem and constitute the fibrous root system

For example, wheat plants.

(c) In other plants, the roots arise from parts of the plant other than the radicle. Such a type of root is called adventitious root—for example, grass, banyan trees etc.

Q3. Write a short note on the stem.

Answer 3- 

The stem is also called the ascending part of the axis as it bears branches, leaves, flowers, and fruits. It originates from the plumule of the embryo, which belongs to a germinating seed. The stem bears internodes and nodes. Nodes are the region of the stem where leaves are born, while on the other hand the internode is the portion between two nodes. The stem is generally green when it’s young and later matures to woody and dark brown.

Q4. What are the main functions of the stem?

Answer 4 – 

The main functions of the stem are  as follows –

(a) Spreading out the branches that bear leaves, flowers, and fruits.

(b) They help to conduct water and mineral transportation. They also help in photosynthesis.

(c) The majority of the stems perform the function of food storage and support. They also provide protection and help in vegetative propagation.

Q5. Describe the important parts of a leaf.

Answer 5-

The leaf consists of three main parts: leaf base, petiole, and lamina.

(a) Leaf base: The leaf base is the part where the leaf is attached to the stem.

(b) Petiole: The petiole gives structural support to the blade.

(c) Lamina: Lamina is the green expanded part of the leaf with veins and veinlets.

Q6. What are the different functions of the petiole and lamina?

Answer 6 –

The major functions of the petiole are 

(a) The petiole helps to hold the blade.

(b) It allows the leaf blades to flutter in the wind, thereby decreasing its temperature and cooling the leaf, which occurs when fresh air is attached to the leaf’s surface.

The functions of the lamina are-

(a) The veins of the lamina help to provide rigidity to the leaf blade.

(b) It acts as a channel that helps to transport water, minerals, and food materials through the plant.

Q7. What do you mean by venation?

Answer 7- 

Venation is the term that describes the arrangement of veins and the veinlets in the lamina of the leaf. The veinlets form a network called reticulate venation, and parallel venation is described when the veins run parallel to each other within a lamina. Dicotyledonous plants mostly possess reticulate venation, while monocotyledonous plants usually possess parallel venation in the lamina of the leaf.

Q 8. Explain the two major types of compound leaves present in plants.

Answer 8 –

The two major types of compound leaves are described:

(a) Pinnately compound leaf: Pinnately compound leaves are present in plants with several leaflets on a common axis called the rachis, which represents the leaf’s midrib as in common plant neem.

(b) Palmately compound leaves: Palmately compound leaves are present in plants where the leaflets are attached at a common point, which is usually present at the tip of the petiole, as in a common plant, silk cotton.

Q9. Describe the term phyllotaxy.

Answer 9 – 

Phyllotaxy is described as the pattern of arrangement of leaves on the stem or branch of a plant.

It is the majority of three main types:

(a) Alternate: Alternate phyllotaxy is when a single leaf arises at each node alternately, the most common example being China rose.

(b) Opposite: Opposite phyllotaxy is when a pair of leaves arise at each node and lie opposite each other. The most common example is Calotropis and guava plants.

(c) Whorled: Whorled phyllotaxy is when more than two leaves arise at a node and form a whorl. The most common example is Alstonia.

Q10. Describe the functions of leaves.

Answer 10 –

(a) Help in the process of photosynthesis. 

(b) Conversion of leaves into tendrils for climbing as seen in peas.

(c) Conversion of leaves into spines for defence as seen in cacti

(d)Storing of food as seen in onion and garlic.

Q 11. Describe the term inflorescence. Name two major types of inflorescences.

Answer 11 –

The inflorescence is the arrangement of flowers on the floral axis of the plant. 

The two major types of inflorescences are – 

(a) Racemose: In racemose inflorescence, the main axis grows, and the flowers grow laterally in acropetal succession.

(b) Cymose: In the cymose inflorescence, the main axis terminates in the flower, and the flowers grow in a basipetal order.

Q 12. What is a flower? How do you describe it?

Answer 12 – 

The flower is classified as the reproductive unit in the angiosperms. It is the primary means for the process of sexual reproduction. A typical flower has four major kinds of whorls arranged successively on the swollen end of the stalk, also known as the pedicel. The four kinds of whorls are calyx, corolla, androecium, and Gynoecium. The androecium and Gynoecium are male and female reproductive organs, while the calyx and corolla are classified as accessory organs.

Q 13. Write a short note on the symmetry of the flower.

Answer 13-

The flower is classified as actinomorphic, which comes in radial symmetry or zygomorphic, which comes in bilateral symmetry. 

(a) Actinomorphic Symmetry: A flower is said to be actinomorphic when divided into two equal radical halves in any radical plane that passes through the centre. Its most common examples are mustard, datura and chilli.

(b) Zygomorphic Symmetry: A flower is said to be zygomorphic when the flower divides into two halves only in one vertical plane, like peas, beans, and cassia.

Q14. Write a short note on the fruit and explain it in detail.

Answer 14 – 

Fruit is classified as a natural or ripened Ovary which develops after fertilisation.

Fruit is also called parthenocarpic fruit because it is formed without the fertilisation of the Ovary.

The fruit consists of a wall, also known as a pericarp and different types of seeds. The pericarp is classified as dry or fleshy. Based on the thickness of the pericarp, it is differentiated into three parts. The outer part is called an epicarp, the middle part is called a mesocarp, and the inner part is known as an endocarp.

Q15. Write a short note on the dicotyledonous seed.

Answer 15 – 

The seed coat is the outermost covering of a seed that helps in protection. The seed coat has two main layers, the outer layer called testa and the inner layer known as tegmen. The developing seeds are attached to the fruit utilising a scar known as the hilum, which is present on the seed coat. The inner region of the seed coat consists of the embryo, which contains an embryonal axis and two cotyledons. These cotyledons are fleshy and filled with reserved food materials. The radicle and the plumule are at the end of the embryonal axis. A small pore called the micropyle is situated above the hilum.

Q16. Write a note on the different regions of the root.

Answer 16 –

At the apex of the root, it is covered by a thumb-like structure called a root cap. The main function of the root cap is the protection of the tender apex of the root that penetrates the soil. The region of meristematic is situated a few millimetres above the root cap. The cells in the meristematic region are small, thin-walled and contain dense protoplasm.

The cells adjacent to this region undergo rapid elongation and enlargement, which are also responsible for the growth of the root. This region responsible for growth is called the region of elongation. The cells in this region gradually differentiate and mature. So, the zone adjacent to the elongation region is called the region of maturation, and root hairs are adjacent to the region of maturation. Root hair consists of epidermal cells that are very fine, delicate, and thread-like structures. The main functions of these root hairs are the absorption of water and minerals from the soil.

Q17. Write a note on different types of leaves and phyllotaxy.

Answer 17- 

A leaf is classified as simple when the lamina of the leaf is incised or entire, and the incisions do not touch the midrib. On the other hand, a leaf is said to be compound when the incisions of the lamina reach up to the midrib and break it into several leaflets. In both simple and compound leaves, a bud is present in the axil of the petiole. However, a bud is not present in the axil of leaflets of the compound leaf.

There are majorly two types of compound leaves; these leaves are classified are:

(a) Pinnately compound leaf

(b) Palmately compound leaf

In a pinnately compound leaf, the number of leaflets is present on a common axis called the rachis, which represents the midrib of the pinnately compound leaf. On the other hand, in palmately compound leaves, the leaflets are attached at a common point, that is, the tip of the petiole.

Phyllotaxy is described as the pattern of arrangement of leaves on the stem or branch of a plant.

It is the majority of three main types:

(a) Alternate: Alternate phyllotaxy is when a single leaf arises at each node in an alternate manner, the most common example being the China rose.

(b) Opposite: Opposite phyllotaxy is when a pair of leaves arise at each node and lie opposite each other. The most common examples are Calotropis and guava plants.

(c) Whorled: Whorled phyllotaxy is when more than two leaves arise at a node and form a whorl. The most common example is Alstonia.

Q18. Write in detail about a  flower.

Answer 18- 

 A flower is classified as the reproductive unit in the angiosperms. It is the primary means for the process of sexual reproduction. A typical flower has four major kinds of whorls arranged successively on the swollen end of the stalk, also known as the pedicel. The four kinds of whorls are calyx, corolla, androecium, and gynoecium. The androecium and gynoecium are male and female reproductive organs, while the calyx and corolla are classified as accessory organs.

The four different whorls are classified as calyx, corolla, androecium, and gynoecium.

(a) Calyx: Calyx is the outermost whorl of the flower containing sepals. Majorly the sepals are green in colour and have a leaf-like structure that protects the flower in the bud stage. The calyx may be gamosepalous, where the sepals are united. Or it can be polysepalous, where the sepals are free. 

(b) Corolla: Corolla is composed of petals that are usually coloured, which attract insects for the process of pollination. The shape of the corolla depends on the structure. It can be tubular, bell-shaped, funnel-shaped, or wheel-shaped.

(c) Aestivation: Aestivation is defined as the arrangement pattern of sepals or petals in the floral bud. The pattern of arrangement depends on the other members of the same whorl. The four main types of aestivations are valvate, vexillary, twisted, and imbricate

(d) Androecium: Androecium is composed of stamens, commonly known as a flower’s male reproductive organ. Each stamen consists of a slender stalk, also called a filament and anther. Each anther is usually bilobed (two lobes). And two chambers (pollen sacs) are present in each lobe. Pollen sacs help in the production of pollen grains. The position of floral parts on the thalamus are Hypogynous, Perigynous and Epigynous

(e) Gynoecium: Gynoecium is the female reproductive part of the flower, which contains the Ovary. It is made up of one or more carpels. A carpel is classified as Ovary, stigma, and style. The stigma is present at the tip of the style, and pollen grains land there. The Ovary is an enlarged structure present in the basal part. The third part, style, connects Ovary to the stigma. Through style, the pollen grain travels. Each Ovary bears an ovule attached to a flattened, cushion-like structure known as the placenta.

A flower may be trimerous, tetramerous or pentamerous, depending on the arrangement of floral appendages.

The flowers are described as hypogynous, perigynous and epigynous on the calyx, corolla, and androecium position. 

Q19. The mature seeds of plants like grams and peas do not possess endosperm. Why?

1. These plants are not classified as angiosperms
2. Double fertilisation does not take place.
3. The Endosperm is not generated in the mature seeds. 
4. During seed development, the endosperm gets used up by the developing embryo.

Answer: Option (d) is the right answer.

Explanation – After fertilisation, the endosperm gets used by the embryo for seed development. 

Q20. In Opuntia, the stem is modified into a flattened green structure that performs the function of photosynthesis. Give two other examples of modifications of the plant parts for the process of photosynthesis.

Answer 20 –

In the plant Australian Acacia, the petiole copies the shape of the leaf and turns green to perform the process of photosynthesis.

In Asparagus, the stem, i.e., about one Internode long, modifies into a leaf-like structure to carry out photosynthesis.

Q21. Differentiate between the following terms –

1. Bracteole and Bract
2. Petiole and Pulvinus
3. Peduncle and Pedicle
4. Spadix and Spike
5. Staminoid and Stamen
6. Pollenium and Pollen

Answer 21 –

1. A bract is always present at the base of the pedicle, whereas on the other hand, a bracteolate is always present between the bract and flower.
2. Pulvinus is the swollen leaf base part present in leguminous plants, whereas, on the other hand, a petiole is a sub-cylindrical stalk that connects the leaf base with the lamina of the leaf.
3. The pedicle is the stalk part of the flower, whereas the peduncle is a stalk part of a whole inflorescence.
4. Spike is the term referred to when the flowers are sessile that develop on an elongated peduncle in acropetal succession, whereas spadix is covered by one of the few large bracts called spates
5. Stamen represents a male reproductive organ, whereas the sterile stamen is called stamina.
6. Pollen is a male gametophyte of angiosperms, whereas polonium is a group of pollen grains.

Q22. Why is a sunflower not a flower? Explain.

Answer 22 –

A sunflower is not classified as a flower because it is a type of inflorescence called a capitulum. In the capitulum, the receptacle is flat, and the whole cluster of florets gets surrounded by bracts. Which are known as an involucre. There are two kinds of florets that are recognised in sunflowers, 

(i) Ray Florets – The Ray Florets are arranged on the rim of the receptacle, which has distinct yellow and strap-shaped petals. These florets are female and sterile. Also, they are always zygomorphic and may be arranged in one or more whorls.

(ii) Disc florets – The Disc Florets are grouped in the centre, bisexual and actinomorphic.

Q23. Define the following terms:

(a) aestivation

(b) placentation

(c) actinomorphic

(d) zygomorphic

(e) superior Ovary

(f) perigynous flower

(g) epipetalous stamen

Answer 23:

1. a) Aestivation is the arrangement pattern of sepals or petals in the floral bud. The pattern of arrangement depends on the other members of the same whorl. The four main aestivation types are valvate, twisted, imbricate and vexillary.

Twisted – The twisted Type of Aestivation occurs when one margin of the appendage overlaps the adjacent one, it can either be clockwise or anti-clockwise. Like in cotton

Valvate – The valvate Type of Aestivation occurs in a whorl when the petals or sepals touch each other at the margin and do not overlap. Like in Calotropis

Imbricate – Imbricate Aestivation occurs when petals or sepals overlap but not in any definite direction. It is mostly found in Gulmohar.

Vexillary Aestivation occurs when the largest petal overlaps the two lateral petals, which in turn overlap the two smallest anterior peels. As seen in the bean flower. 

1. b) Placentation is defined as the arrangement of ovules within the ovary. They are five main types –

Marginal Placentation – In this type, the placenta forms a ridge along the ventral suture of the Ovary, so the ovules are borne on the ridge to form two rows. Example – Pea

Axile Placentation – Placenta is axial, and ovules are attached to it in a multilocular ovary. Example – lemon

Parietal Placentation – In this Type, the ovules develop on the inner wall of the Ovary or the peripheral wall. It is mostly single-chambered, but due to the formation of a false septum, it becomes two-chambered. Example- Mustard

Basal Placentation – The placenta develops at the base of the Ovary, wherein a single ovule is attached to it. Example – Marigold.

Free central Placentation – In this Type, the ovules are borne on the central axis, and the septa are absent. One common example is primrose.

1. C) Actinomorphic flowers are flowers which can be divided into two halves by any vertical plane. Example – Chilli
2. d) Flower, which has bilateral symmetry and can be divided into two halves only in one plane, is known as a zygomorphic flower. Example – Gulmohar
3. e) In the Hypogynous flower, the Gynoecium occupies the highest position while other parts remain below it. The Ovary in such a flower is known as the superior Ovary. Example – Brinjal

f)A perigynous flower is one in which the gynoecium is situated in the centre, and other parts of the flower are located on the rim of the thalamus. The Ovary is half inferior. Example – Rose

1. g) Epipetalous stamen – Instead of directly being inserted over the thalamus, it has a stamen borne over a petal. Example – Brinjal

Q24.Describe the arrangement of floral members about their insertion on the thalamus.

Answer 24 – Flowers may be explained into three kinds based on the position of the calyx, corolla & androecium in respect of ovaries on the thalamus. 

(a). HYPOGYNOUS FLOWERS:- Gynoecium located at highest position & rest whorls of flower lies below it. e.g., mustard, China rose. 

(b). PERIGYNOUS FLOWERS: – The Gynoecium is situated in the centre. Other parts of the flower lie on the rim of the thalamus, almost at the same level. The Ovary is half inferior, e.g., plum rose.

 (C)EPIGYNOUS FLOWERS: – The margins of the thalamus grow upwards, enclosing the Ovary fully & getting to it. The rest of the flower rises above the Ovary. i.e., Ovaries are inferior to these flowers. E.g., guava, sunflower, cucumber.

Q25. How do various leaf modifications help plants?

Answer 25 

The normal functions of leaves are photosynthesis, respiration & transpiration. Besides these functions, the leaves must perform other functions. Hence, they modify themselves in different ways:

(i)TENDRIL: – In some plants, the entire leaf or part is modified to a coiled thread-like structure called tendrils. Tendrils Help Plants to climb up, e.g., peas and clematis.

 (ii)SPINES: – In many plants, the leaves or their apices are modified into thin sharp & pointed structures known as spines. They help in defence. Opuntia, yucca. etc.

 (iii)SCALE LEAVES: – In onions, mostly all the leaves are in the form of fleshy scale leaves. 

(iv)PITCHER:- It is the modification of a leaf in an insectivorous plant in which the lamina takes the form of the pitcher, the apex the form of a lid to trap the insects. There are several digestive glands in the inner walls of the pitcher—these Gland Secrete Fluid Which Digests insects, e.g., Nepenthes. 

(v)PHYLLODE: -The petiole becomes green, flattened leaf-like is called phyllode, e.g. Australian Acacia.

Q26. Describe the sub-aerial modifications of the stems.

Answer 26: The main function of sub-aerial modification of stems is vegetative propagation. They are of the following types:

(i)Runners: – They contain stems that are long & thin with branches which creep along the ground & develop roots at the nodes. The mother plant produces many branches that are spread out in all directions. They can break off and get classified as independent plants. The most common plant is oxalis, doob grass. 

(ii)STOLON: – This is also a thin lateral branch arising from the stem’s base. It grew upward and bent down again, developing roots at the tip & producing a bud. The bud grows into a new plant, e.g., mint and strawberry.

(iii)OFFSET: – This is a thickened horizontal branch arising in the axil of a lower leaf. It is a short branch which produces a cluster of leaves above & tufts of roots below. The offset can break off from the mother plant & start living an independent life: E.g. Water lettuce, water hyacinth.

(iv)SUCKER: – The sucker is a lateral branch that develops from the stem’s underground part. It grows upward in an oblique manner & directly gives rise to new plants.

Q27. What are the various modifications of adventitious roots? Explain it with examples.

Answer 27- 

 MODIFICATIONS OF ADVENTITIOUS ROOTS:

(i)Tuberous Adventitious root: – It is a swollen root which does not have a definite shape. The most common example is sweet potato. 

(ii)Fasciculated Adventitious root: – When several tuberous roots arise from the same place in a cluster, they are termed fasciculated roots. The most common example is the dahlia, Asparagus. 

(iii)Beaded Adventitious root: – These roots frequently contain swollen parts, like in portulaca and Vitis.

 (iv)Prop roots: – Prop roots are pillars-like roots hanging vertically downward from the aerial branch of the plant. The most common example is the Banyan tree.

 (v)Stilt roots: – Stilt roots are short and grow obliquely from near the base of the main stem. They provide anchorage & support to the stem. The most common examples are sugarcane, maise, and sorghum.

(vi) Parasitic Roots: – These roots penetrate the host cells & absorb nutrients from the host tree, e.g. Cuscuta.

 (vii)ASSIMILATORY ROOTS: – Adventitious roots in certain plants become green to carry out photosynthesis & are called assimilatory roots, e.g. Tinospora, trapa.

Q28. Roots obtain Oxygen from the air for the process of respiration. In the absence or deficiency of Oxygen, the root growth gets restricted and stops completely. So how do the plants growing in marshlands or swamps obtain the Oxygen required for root respiration?

Answer 28 –

The plants that grow in marshlands or swamps generate vertical growth from their roots. These roots are hollow from within, and thus air enters through these roots. These roots are known as pneumatophores. These pneumatophores assist the plants in swamps and marshland areas in acquiring oxygen for root respiration.

Q29. Rearrange the following zones as observed in the vertical section of the roots and choose the correct option.

1. Root hair zone
2. Zone of meristems.
3. Rootcap zone
4. Zone of maturation
5. The zone of elongation

The following options are – 

(a) C, B, E, A, D

(b) A, B, C, D, E

(c) D, E, A, C, B

(d) E, D, C, B, A

Answer 29 – The correct answer is an option (a) C, B, E, A, D

Explanation: The root cap is present at the tip, followed by a zone of meristematic tissue. This is further followed by the zone of elongation and then by the root hair zone. The zone of maturation comes after all of them at the base. 

Q30. Give two examples of roots that develop from different parts of the angiosperms plant other than the radicle.

Answer 30 –

Adventitious roots are used when the roots develop from different plant parts in angiosperms. Two examples of adventitious roots are: –

Prop Roots of Banyan: The roots of a banyan tree are an example of prop roots. These prop roots penetrate deeply into the soil and help the tree maintain balance and support itself.

Stilt Roots in Maise: The roots in maise plants exemplify stilt roots. These stilt roots enter the ground and are developed from the nodes just above the ground; they provide extra support and hoist the main plant.

Q31. The essential functions of roots are anchorage and absorption of water and minerals in the terrestrial plant. What functions are associated with the roots of aquatic plants? How are the roots of aquatic plants and terrestrial plants different?

Answer 31- 

The most important function of roots is to provide anchorage and also help the plant absorb water and minerals. Since the availability of water is not an issue for aquatic plants, the roots are not properly developed in most aquatic plants. In these aquatic free-floating plants, the roots are very few and are in a structure of fine hairs. Roots play an important role in anchorage in the plants that are submerged.

Q32. How can you differentiate between free central and axile placentation?

Answer 32-

Placentation is considered free central when the septa are absent, and the ovules are born on the central axis.

Placentation is regarded as axile when the placenta is axial, and the ovules are attached to the placenta in a multilocular ovary.

Q33. Tendrils are found in the following plants. Identify whether they are stem tendrils or leaf tendrils.

1. Cucumber
2. Peas
3. Pumpkins
4. Grapevine
5. Watermelons

Answer 33 –

1. Cucumber – Stem tendrils
2. Peas – Leaf tendrils
3. Pumpkins – stem tendrils
4. Grapevines – stem tendrils
5. Watermelons – stem tendrils

Q34. Describe various stem modifications associated with food storage, climbing and protection.

Answer 34 –

The various stem modifications that help with food storage, climbing, and protection are as follows: –

For food storage, underground stems of ginger, turmeric, potato, and colocasia are modified. These stems also function as organs of perennation that help gets over unfavourable growth conditions.

Developed from axillary buds, stem tendrils are spirally coiled and slender, which helps the plants to climb. Some examples include grapevines, pumpkins, cucumbers, watermelons etc.

It is possible for the axillary buds of the stems to be modified into straight, woody and pointed thorns. Some famous examples are Citrus and Bougainvillaea. Thorns help to protect plants from animals.

Q35. What is meant by the term modification of root? What type of modification of root is found in the following examples?

(a) Banyan tree

(b) Turnip

(c) Mangrove trees

Answer 35 – 

Primarily, there are three types of root systems found in plants: the tap root system, adventitious root system and fibrous root system. In the majority of dicotyledonous plants, direct elongation of the radicle takes place, which leads to the formation of primary roots, and this primary root grows inside the soil. Further, the primary roots and their branches constitute the taproot system, for example-mustard plants.

In most monocotyledonous plants, the primary root is short-lived and is majority replaced by many roots. Further, the primary roots originate from the base of the stem and constitute the fibrous root system. For example, wheat plants. In other plants, the roots arise from parts of the plant other than the radicle. Such a type of root is called adventitious root—for example, grass, banyan tree etc.

Roots and their modifications in various plants:

(a) Banyan tree

The banyan tree, scientifically called Ficus benghalensis, has massive pillar-like adventitious roots arising from the aerial part of the stem towards the ground. They provide support to the tree, and such roots are called prop roots.

(b) Turnip

The roots of turnip, which is scientifically called Brassica rape, help in food storage. Similar types of these food-storing roots are found in radishes, carrots, and sweet potatoes.

(c) Mangrove tree

The plants that grow in marshlands or swamps, like a mangrove tree, have vertical growths generated from their roots. These vertical roots are hollow from within, and thus air enters through these roots. These roots are known as pneumatophores. These pneumatophores assist the plants in swamps and marshland areas in acquiring oxygen for root respiration.

Q36. Differentiate between the following terms-

(a) Cymose and Racemose Inflorescence

(b) Adventitious and Fibrous roots

(c) Syncarpous and Apocarpous Ovary

Answer 36- 

(a) In the racemose inflorescence, the younger flowers are present at the tip, while the older flowers are arranged at the base of the inflorescence. Such an arrangement is classified as acropetal succession. And the main axis in racemose inflorescence continues to grow and produce flowers laterally. While in a cymose inflorescence, the younger flowers are at the base of the inflorescence, and the older flowers are at the top. Such an arrangement is classified as basipetal succession. The main axis in cymose inflorescence has limited growth, which later terminates into a flower.

(b) In most monocotyledonous plants, the primary root is short-lived and is mostly replaced by many roots. Further, the primary roots originate from the base of the stem and constitute the fibrous root system

For example, wheat plants.

In other plants, the roots arise from parts of the plant other than the radicle. Such Types of roots are called adventitious roots—for example, grass, banyan tree etc.

(c) In the Apocarpous Ovary, the flowers have more than one carpel, and these carpels are free-living. It is commonly observed in lotus and rose flowers. 

While on the other hand, the flowers with syncarpous Ovaries also contain more than one carpel, but these carpels are fused, as seen in tomato and mustard. 

Q37. Describe different modifications of the stem.

Answer 37 – 

The stem is also called the ascending part of the axis, as it bears branches, leaves, flowers, and fruits. It originates from the plumule of the embryo, which belongs to a germinating seed. The stem bears internodes and nodes. Nodes are the region of the stem where leaves are born, while on the other hand the Internode is the portion between two nodes. The stem is generally green when it’s young and later matures to woody and dark brown. The stems are generally modified into four main parts: Underground stems or storage stems, supportive stems, and protective and photosynthetic stems. 

The main functions of the stem are stated as follows –

(a) Spreading out the branches that bear leaves, flowers, and fruits.

(b) They help to conduct water and mineral transportation. They also help in photosynthesis.

(c) The majority of the stems perform the function of food storage and support. They also provide protection and help in vegetative propagation.

Q 38. Take a flower each from the families of Fabaceae and Solanaceae and then write its semi-technical description.

Answer 38 – 

(1) Family Fabaceae/Papilionaceous (pea plant)

Fabaceae, also called Papilionaceous, is a sub-family classified under the Leguminosae family.

Vegetative features of Family Fabaceae:

Pinnately compound leaf type alternately arranged with leaf tendrils with the Pulvinus present at the leaf base along fallacious stipules. It is classified under the tap root system with root nodules.

Floral features are described as follows:

Inflorescence: Racemose Inflorescence, generally axial than terminal

 Zygomorphic and bisexual flowers contain five gamosepalous sepals, and the aestivation is imbricate.

Corolla: It contains five petals, i.e., polypetalous with vexillary aestivation.

Androecium: The Androecium consists of ten anthers diadelphous with dithecous anthers. At the same time, the Gynoecium contains a monocarpellary superior Ovary, unilocular with marginal placentation.

Fruit: Legume pod with non-endospermic seeds

Economic importance: The most common example is Peas, used as vegetables for various culinary preparations.

2) Flowers of Solanum nigrum (Family Solanaceae)

Vegetative features of Family Solanaceae:

It contains an erect, herbaceous plant with simple, exstipulate leaves that contain reticulate venation. 

It has an erect stem that has numerous branches.

Floral features are classified as:

Solitary and axillary inflorescence with actinomorphic, bisexual flowers containing calyx composed of five sepals which are united and persistent. The aestivation is valvate, and the corolla consists of five united petals.

Androecium: The Androecium consists of five epipetalous stamens, while the other hand, Gynoecium consists of a carpellary syncarpous superior Ovary with axile placentation.

The most common example is Berry

Seeds: Numerous endosperms

Economic importance: Used for medicinal purposes.

Q 39. Please describe aerial modifications of the stem which are highlighted in Biology Class 11 Chapter 5.

Answer 39. Aerial modifications of the stem could be any of the ones as follows: –

1. a) Stem Tendril: – Stem tendrils are very thin and slender-like, sometimes spirally coiled structures that develop from axillary buds. They are found in the plants such as cucumber, watermelon, grapevine etc. and they help these plants to climb.
2. b) Stem Thorn: – Axillary buds may sometimes grow into hard, woody straight & pointed structures which are also called thorns. The thorns arise in the axil of the leaf or at the tip of the branch. Sometimes thorn bears leave also as can be seen in Citrus plants as well as in Bougainvillaea etc.
3. c) Phylloclade: – This is the green flattened or cylindrical stem which looks and performs the function of the leaf. They contain chlorophyll & also carry out photosynthesis. They have many nodes & internodes and have scaly leaves or shortened spines. These are mostly found in xerophytic plants like opuntia, epiphyllum etc. 
4. d) Cladode: – This is a phylloclade of limited growth which develops, from the node of the stem or branch and in the axil of a scale leaf. Cladodes are green flat and leaf-like structures that carry on photosynthesis. Example: – Asparagus, Ruscus, etc.
5. e) Bulbils: – This is a modified vegetative or floral bud meant to produce a new plant. It detaches itself from its mother plant and grows into an independent plant. Example: – Oxalis, Agave americana, Lilium.

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