NEET Biology Anatomy of Flowering Plants Important Questions Set 02

These Class 11 NEET Biology important questions on Anatomy of Flowering Plants give 23 questions with step-by-step answers, arranged as very short, short and long answer types, taken from a model test paper. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. Which phloem element is absent in most of the monocotyledons?
Answer: Phloem parenchyma

Question 2. Name the waxy layer that often covers the epidermis.
Answer: Cuticle

Question 3. Which type of vascular bundles are found in leaves?
Answer: Conjoint type

Question 4. What is the shape of endodermal cells?
Answer: Endodermal cells are barrel-shaped.

Question 5. What is the location of pericycle w.r.t. endodermis in a dicotyledonous stem?
Answer: Pericycle lies on the inner side of the endodermis.

Question 6. Bulliform cells are present in which organ of the grasses?
Answer: Leaves

Question 7. Which cells in the dicotyledonous stems give rise to interfascicular cambium?
Answer: Cells of primary medullary rays.

Question 8. Name the cells that rupture the epidermis and result in formation of lenticels in most woody trees.
Answer: Complementary cells

Short Answer Type Questions

Question 9. What do you understand by permanent tissue? Give two examples.
Answer: Permanent cells are also called mature cells. They are formed following divisions of the cells in primary and secondary meristems. These are structurally and functionally specialised cells that have lost the ability to divide. For example, parenchymatous cells, sclerenchymatous cells, etc.

Question 10. Name various phloem elements in gymnosperms.
Answer: Gymnosperms have albuminous cells, sieve cells, phloem fibres and phloem parenchyma. They lack sieve tubes and companion cells. Sieve cells are not arranged in linear rows and possess sieve plates on their lateral walls. Sieve cells conduct the water and minerals.

Question 11. What are stomata?
Answer: Stomata are the structures present in the epidermis of leaves. Each stoma is composed of two bean-shaped cells called guard cells which enclose the stomatal pore. Stomata regulate the process of transpiration and gaseous exchange.

Question 12. Discuss the zonation of a dorsiventral leaf.
Answer: The vertical section of a dorsiventral leaf through the lamina shows three main parts, namely, epidermis, mesophyll and vascular system. The epidermis covers both upper and lower surfaces of the leaf. The tissue between the upper and lower epidermis is called mesophyll.

Question 13. Define intrafascicular and interfascicular cambium.
Answer: The cells of cambium present between primary xylem and primary phloem or within the vascular bundle comprise the intrafascicular cambium. Also called fascicular cambium. The cells of cambium present in between the vascular bundles, formed by the division of cells of primary medullary rays, comprise the interfascicular cambium.

Question 14. Why do primary and secondary phloems get gradually crushed during the secondary growth of dicot stems?
Answer: Secondary xylem and secondary phloem are produced by the cambial ring. The cambial ring is generally more active on the inner side than on the outer. As a result, the amount of secondary xylem produced is more than secondary phloem. The primary and secondary phloems get gradually crushed due to the continued formation and accumulation of secondary xylem as phloem is a weak tissue.

Question 15. From where does the cork cambium arise in dicot roots and what happens to the layers peripheral to phellogen during secondary growth?
Answer: Cork cambium, in dicot roots, originates from the cells of pericycle and all the tissues lying outside or peripheral to phellogen (cork cambium), i.e., primary cortex and epidermis die and completely slough off due to the increasing pressure on them as a result of continued activity of cork cambium.

Short Answer Type Questions

Question 16. Discuss about phloem fibres and also explain their commercial use, if any.
Answer: Phloem fibres are made up of sclerenchymatous cells. These are much elongated, unbranched cells that have pointed, needle-like apices. The cell walls of fibres is quite thick. At maturity, these fibres lose their protoplasm and become dead. Phloem fibres of jute, flax and hemp are used commercially to form bags, ropes, paper, textile fabrics for clothes, etc.

Question 17. Differentiate between epidermis, hypodermis and endodermis.

Answer:

Epidermis Hypodermis Endodermis
(i) It is the outermost layer of (i) It is the outer zone of the (i) It is the innermost layer of the primary plant body. cortex. the cortex.
(ii) It is present in both stems (ii) This zone is absent in the (ii) It is present in both stems and roots. roots. and roots.
(iii) E p i d e r m i s p r o v i d e s (iii) It is also protective in (iii) It acts like the dam between

Question 18. Differentiate dicotyledonous and monocotyledonous roots on the basis of stele.

Answer:

All tissues on the inner side of the endodermis such as pericycle, vascular bundles and pith constitute the stele. Dicot and monocot roots can be differentiated on the basis of stele as follows :

Component of stele Dicot root Monocot root
(i) Pericycle Gives rise to both lateral roots and Gives rise to lateral rootsonly. vascular cambi um during secondary growth.
(ii) Vascular bundles Diarch to hexarch as usually 2 to 6 Polyarch as usually more than 6 xylem bundles are present xylem bundles are present.
(iii) Pith Small and inconspicuous. Large and well developed.

Question 19. The heartwood is more durable than sapwood. Why?
Answer: The heartwood is more durable because it is resistant to the attacks of microorganisms and insects. This resistance is derived due to the deposition of organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils in their vessels and tracheids. These substances prevent the easy decay of heartwood. On the other hand, younger layers of secondary xylem, i.e., sapwood does not possess the above mentioned organic compounds and hence is less durable than heartwood.

Question 20. Fill in the blanks :
(a) The parenchymatous cells which lie between the xylem and the phloem are called ________ in root.
(b) Hypodermis is ________ in dicot stems while ________ in monocot stems.
(c) Bark is a non-technical term that refers to all tissues exterior to the ________.
Answer: (a) Conjuctive tissue
(b) Collenchymatous, sclerenchymatous
(c) Vascular cambium

Question 21. Explain
(a) Early wood and late wood
(b) Early bark and late bark
Answer: (a) Early wood : Also called spring wood. It is produced due to the more activity of vascular cambium in spring season. It has a large number of xylary elements having vessels with wider cavities. Late wood : Also called autumn wood. It is produced due to less activity of vascular cambium in winter season. It has fewer xylary elements having narrow vessels.
(b) Early bark : Bark that is formed early in the season is called early bark. It is also called soft bark. Late bark : Bark that is formed late in the season is called late bark. It is also called hard bark.

Long Answer Type Questions

Question 22. Differentiate between monocotyledonous and dicotyledonous stem. OR Diagrammatically explain the process of secondary growth in dicot roots.

Answer:

Character Dicotyledonous stem Monocotyledonous stem
(i) Ground tissue Differentiated into cortex and pith. Not differentiated into cortex and pith.
(ii) Hypodermis Collenchymatous Sclerenchymatous.
(iii) Endodermis Single layered Absent
(iv) Pericycle Made up of parenchymatous and / Absent or sclerenchymatous cells.
(v) Vascular bundles  Arranged in a ring.  Scattered  Conjoint and open.  Conjoint and closed.  Bundle sheath absent.  Bundle sheath present.  Phloemparenchyma present.  Phloemparenchyma absent.  Water-containing cavities are  Present absent.
(vi) Pith Present and well developed. Absent
(vii) Medullary rays Present Absent OR

Secondary growth in dicot roots : The secondary growth in dicot roots is the result of activities of vascular and cork cambium.

(a) Origin and activity of vascular cambium : In dicot roots, the arrangement of vascular bundles is radial and exarch.

Cambium is absent but develops at the time of secondary growth. First of all, parenchyma cells interior to phloem (towards pith) become meristematic, thus, in a tetrach root, four separate strips of cambia are formed. Later these strips become continuous laterally as a result of tangential divisions of the cells of pericycle opposite to each protoxylem. Thus, a wavy continuous cambium ring is produced. This cambium ring later becomes circular and cuts off secondary xylem internally and secondary phloem externally.

Epiblema Cortex Pericycle Endodermis Cambium Primary phloem Secondary phloem A Primary xylem B Secondary xylem Cork Phellogen

Primary phloem Medullaryray

Primary xylem Secondary xylem Primary C phloem Cambium D Secondary phloem

(b) Origin and activity of cork cambium : Cork cambium arises as a result of the tangential divisions of the outer cells of pericycle. The activity of cork cambium is similar to that found in dicot stem so it produces cork cells on the outer side and parenchyma (secondary cortex) on the inner side.

The cork cells become suberized and become dead due to further suberin deposition. As the cork cambium in dicot root originates from the cells of pericycle so all tissues lying outside the cork (primary cortex, epidermis) are completely sloughed off.

Question 23. (a) Write short notes on the following :
(i) Conjoint type of vascular bundles
(ii) Starch sheath
(b) How phellogen gives rise to the lenticels?
OR
(a) Write short notes on the following :
(i) Cuticle
(ii) Spongy parenchyma
(b) How do bulliform cells minimise the water loss?

Answer:

(a) (i) Conjoint type of vascular bundles : The xylem and the phloem together constitute vascular bundles. In conjoint type of vascular bundles, the xylem and phloem are situated at the same radius of vascular bundles. Such vascular bundles are common in stems and leaves. These may further be divided into open and closed type on the basis of presence or absence of vascular cambium, respectively.

(ii) Starch sheath : Endodermis is called the starch sheath. It is the innermost layer of the cortex in dicot stem. The cells of the endodermis are rich in starch grains as they store these grains in them. These starch grains are produced as a result of photosynthesis in leaves.

(b) Lenticel is a small portion of periderm. Lenticels are produced at the places where the activity of phellogen is more than elsewhere which produces loosely arranged, thin-walled cells with numerous intercellular spaces, instead of thick-walled suberized cork cells. These thin-walled cells are called complementary cells. As the number of complementary cells increases, it creates pressure on the epidermis forming small protuberance. These protuberances burst the epidermis to form lenticels. Lenticels permit the exchange of gases between the plant and outer atmosphere and are responsible for loss of water vapour also.

OR

(a) (i) Cuticle : Cuticle is the protective, waxy covering on the outer walls of cells of epidermis. Cuticle minimises the water loss. It also prevents the entry of pathogens due to its waxy secretion. The main structural component of cuticle is cutin. Cuticle is absent in roots.

(ii) Spongy parenchyma : Spongy parenchyma lies below the palisade parenchyma in the dicotyledonous leaves. It is the part of mesophyll. It comprises of oval or round shaped cells. Spongy parenchyma extends below to the lower epidermis. There are numerous large spaces and air cavities between the cells of spongy parenchyma.
(b) Bulliform cells are the specialised epidermal cells in grasses. Certain adaxial epidermal cells or the cells present on upper epidermis along the veins of leaves modify themselves into large, empty and colourless cells called bulliform cells. These minimise the water loss. When they have absorbed the water and are turgid, the leaf surface is exposed. This occurs during ample water supply to the plant. But when the plant suffers from the water stress, these cells become flaccid by losing water, they make the leaves curl inwards so that the latter are not exposed hence water loss is minimised.