CBSE Class 11 Biology Anatomy of Flowering Plants Assignments

Very Short Answer Questions (1 mark each)

Question 1. Name the tissue represented by the jute fibres used for making the ropes.
Answer: Sclerenchyma.
In simple words: Jute fibres are made of sclerenchyma cells, which have thick, lignified walls that provide high tensile strength.

Exam Tip: Remember that mechanical support tissues in plants are mainly collenchyma and sclerenchyma; dead supportive cells with thick secondary walls are sclerenchyma (fibres and sclereids).

Question 2. Which kind of roots have polyarch vascular bundles?
Answer: Monocotyledonous roots.
In simple words: Monocot roots typically contain more than six xylem and phloem bundles, making them polyarch.

Exam Tip: Dicot roots generally have 2 to 5 vascular bundles (diarch to pentarch), whereas monocot roots have polyarch bundles (more than six).

Question 3. What is heart wood?
Answer: The hard central region of a tree trunk made up of dead, non-functional xylem vessels filled with organic compounds such as tannins, resins, and oils.
In simple words: Heartwood is the dark, durable, non-conducting central wood of old trees that provides structural support.

Exam Tip: Contrast heartwood with sapwood: heartwood does not conduct water, whereas sapwood is involved in water and mineral conduction.

Question 4. State the role of pith in stem.
Answer: Pith stores food material and helps in the transport of water and minerals radially.
In simple words: Pith is the central region of parenchymatous tissue that stores nutrients.

Exam Tip: Pith is well-developed in monocot roots and dicot stems, but often absent or very small in dicot roots.

Question 5. Where are bulliform cells found in leaves?
Answer: Bulliform cells are found in the upper epidermis of monocot leaves.
In simple words: These specialized, large, empty-looking epidermal cells help in leaf rolling to minimize water loss during stress.

Exam Tip: Associate bulliform cells directly with grasses and monocot leaves and their role in withstanding water stress.

Question 6. Which meristem does produce growth in length?
Answer: Primary meristem (Apical meristem and intercalary meristem).
In simple words: Apical meristems at the tips of roots and shoots increase the length of the plant body.

Exam Tip: Primary meristems add to primary growth (length), while secondary meristems add to secondary growth (girth/thickness).

Question 7. What forms the cambial ring in a dicot stem during the secondary growth?
Answer: The intrafascicular cambium (present inside vascular bundles) and interfascicular cambium (formed by medullary rays) together form the continuous cambial ring.
In simple words: The cambial ring is created by joining existing cambium inside bundles with newly formed cambium between them.

Question 8. Name the anatomical layer in the root from which the lateral branches of root originate.
Answer: Pericycle.
In simple words: Lateral roots arise endogenously from the pericycle layer.

Exam Tip: Remember that lateral roots are endogenous in origin because they develop from the internal pericycle layer.

Question 9. Which tissue of the leaf contains chloroplast?
Answer: Mesophyll tissue.
In simple words: Mesophyll cells contain numerous chloroplasts and carry out photosynthesis.

Exam Tip: In dorsiventral leaves, mesophyll is differentiated into palisade and spongy parenchyma, both rich in chloroplasts.

Question 10. A plant tissue when stained, showed the presence of hemicellulose and pectin in cell wall of its cells. Name the tissue.
Answer: Collenchyma.
In simple words: Collenchyma cell walls show uneven thickenings due to the deposition of cellulose, hemicellulose, and pectin.

Exam Tip: Cellulose alone = Parenchyma; Cellulose + Hemicellulose + Pectin = Collenchyma; Lignin = Sclerenchyma.

Short Answer Question-II (2 marks each)

Question 11. Give the function of lenticels.
Answer: Lenticels permit the exchange of gases between the internal tissues of woody stems and roots and the external atmosphere.
In simple words: They act as breathing pores in the bark of woody plants.

Exam Tip: Lenticels remain open continuously, unlike stomata which can regulate their opening and closing.

Question 12. The vascular bundles are surrounded by a thick layer of cells. What is the name of the cells?
Answer: Bundle sheath cells.
In simple words: Vascular bundles in leaves and certain stems are enclosed by a protective sheath of cells.

Exam Tip: In C4 plants, bundle sheath cells are prominent and play a key role in Kranz anatomy.

Question 13. Where are casparian strips found?
Answer: Casparian strips are found in the radial and tangential walls of the endodermal cells of roots.
In simple words: They are water-impermeable bands present in root endodermis.

Exam Tip: Casparian strips are composed of suberin, which prevents apoplastic movement of water into the vascular cylinder.

Question 14. Give the function of companion cells.
Answer: Companion cells maintain the pressure gradient in sieve tubes and assist sieve tube elements in loading and unloading of sugars.
In simple words: They control the metabolic activities of the enucleated sieve tube elements.

Exam Tip: Companion cells are specialized parenchymatous cells closely associated with sieve tube elements through pit fields.

Question 15. Why is cambium considered to be lateral meristem?
Answer: Cambium is considered a lateral meristem because it occurs along the lateral sides of stems and roots, appears later than primary meristem, divides periclinally, and increases the thickness (girth) of the plant body.
In simple words: It adds secondary tissues that widen the plant stem or root.

Exam Tip: Examples of lateral meristems include vascular cambium and cork cambium (phellogen).

Question 16. Give any four differences between tracheids and vessels.
Answer:
1. Tracheids are formed from a single cell, whereas vessels are made of a column of many cells joined end-to-end.
2. Tracheid ends are rounded or transverse, whereas vessel ends are generally oblique and tapering or transverse with perforations.
3. Tracheids are comparatively narrower, whereas vessels are comparatively wider.
4. Tracheids have pitted walls without open end plates, whereas vessels have perforated end plates allowing unobstructed water flow.
In simple words: Vessels are more efficient water-conducting tubes made of multiple cells, while tracheids are single-celled tubular elements.

Exam Tip: Both are dead, lignified xylem elements, but vessels are characteristic of angiosperms (though absent in some primitive ones like Winteraceae).

Question 17. How are open vascular bundles differ from closed vascular bundles?
Answer: Open vascular bundles contain a strip of cambium in between xylem and phloem (allowing secondary growth), whereas closed vascular bundles lack cambium and do not undergo secondary growth.
In simple words: Open bundles can form secondary tissues, while closed bundles cannot.

Exam Tip: Dicot stems have open bundles; monocot stems have closed bundles.

Question 18. What are trichomes? State their functions.
Answer: Trichomes are multicellular epidermal outgrowths on the stem, leaves, flowers, or fruits. Functions: They help in protection against herbivores, reduce water loss by transpiration, and sometimes aid in seed dispersal.
In simple words: Hairs on the plant surface that protect against water loss and animals.

Exam Tip: Distinguish between unicellular root hairs and multicellular epidermal trichomes.

Question 19. Given below are the various types of tissue and their functions. Which out of these is not a matching pair and why:
(a) Collenchyma : provides mechanical support to the growing parts of plant.
(b) Sclerenchyma : photosynthesis, storage and secretion.
(c) Chlorenchyma : perform the function of photosynthesis.
Answer: Pair (b) is not a matching pair. Reason: Sclerenchyma consists of dead cells with lignified walls whose primary function is to provide mechanical rigidity and support to plant organs, not photosynthesis, storage, or secretion (which are functions of living parenchyma).
In simple words: Sclerenchyma provides mechanical strength; it does not perform photosynthesis.

Exam Tip: Always match living parenchyma with storage/photosynthesis and dead sclerenchyma with mechanical support.

Short Answer Question-I (3 marks each)

Question 20. Differentiate between endarch and exarch conditions.
Answer:
Endarch condition: Protoxylem lies towards the centre (pith) and metaxylem towards the periphery. It is typically found in stems.
Exarch condition: Protoxylem lies towards the periphery and metaxylem towards the centre (pith). It is typically found in roots.
In simple words: In stems, old xylem is inside and new is outside; in roots, it is the reverse.

Exam Tip: Mnemonics: Exarch = External protoxylem (roots); Endarch = Internal protoxylem (stems).

Question 21. If you are provided with microscopic preparation of transverse section of a meristematic tissue and permanent tissue, how would you distinguish them?
Answer:
1. Meristematic tissue: Cells are actively dividing, small, isodiametric, thin-walled with dense cytoplasm, prominent nuclei, and lack intercellular spaces.
2. Permanent tissue: Cells have lost the capacity to divide, may be living or dead, possess definite shapes and sizes, larger vacuoles, and often have intercellular spaces or thickened secondary walls.
In simple words: Meristematic cells are compact, thin-walled and dividing; permanent cells are differentiated and specialized.

Exam Tip: Key identifying features for meristematic cells: dense cytoplasm and prominent nucleus without large vacuoles.

Question 22. Differentiate between aerenchyma and collenchyma on the basis of their structure and function.
Answer:
Aerenchyma: (a) Parenchymatous tissue containing large air spaces. (b) Thin-walled cells, isodiametric in shape. (c) Provides buoyancy to aquatic plants to help them float.
Collenchyma: (a) Tissue containing deposits of cellulose and pectin at the corners of cells. (b) Consists of oval, spherical, or polygonal living cells without intercellular spaces. (c) Provides mechanical strength and elasticity to growing plant organs.
In simple words: Aerenchyma has air cavities for floating in water plants; collenchyma has corner thickening for flexible mechanical support.

Exam Tip: Aerenchyma is a specialized form of parenchyma adapted for aquatic life (hydrophytes).

Question 23. Are there any tissue elements of phloem which are comparable to those of xylem? Explain.
Answer: Yes, certain phloem elements are comparable to xylem elements:
(a) Sieve elements of phloem are comparable to vessels of xylem because both lack a nucleus at maturity.
(b) Phloem fibres are similar to xylem fibres (wood fibres) because both provide mechanical support and possess thick, lignified walls.
(c) Phloem parenchyma and xylem parenchyma are both living parenchymatous components serving storage functions.
In simple words: Phloem fibres and xylem fibres share mechanical functions, while sieve tubes and vessels both lack nuclei as functional conduits.

Exam Tip: Focus on the analogies: Sieve tube matches vessel, phloem fibre matches xylem fibre, phloem parenchyma matches xylem parenchyma.

Question 24. Palm is a monocotyledonous plant, yet it increases in girth. How is it possible?
Answer: Although palms are monocots and lack a typical vascular cambium, they increase in girth through anomalous secondary growth. A secondary meristem arises in the hypodermal region of the stem which produces conjunctive tissue and patches of meristematic cells, resulting in the formation of secondary vascular bundles and thickening of the stem.
In simple words: Palms undergo abnormal secondary thickening through specialized meristematic activity in the outer cortex.

Exam Tip: Normal secondary growth is absent in monocots, but exceptional anomalous secondary growth occurs in trees like Palm, Yucca, and Dracaena.

Question 25. Observe the figure and answer the following questions:
(i) Name parts (a) and (b).
(ii) Are these types of stomata observed in monocot or in dicot plants?
(iii) Which parts of stomata constitute the stomatal apparatus?
Answer:
(i) (a) Epidermal cell (or subsidiary cell), (b) Guard cell.
(ii) Dicot plants (as indicated by kidney-shaped guard cells).
(iii) The stomatal apparatus includes the stomatal aperture, guard cells, and the surrounding subsidiary cells.
In simple words: (a) Subsidiary cell, (b) Guard cell; kidney-shaped guard cells are typical of dicots.

Exam Tip: Dicot guard cells are bean or kidney-shaped, whereas monocot guard cells are dumbbell-shaped.

Long Answer Questions (5 marks each)

Question 26. (i) What are meristems?
(ii) Name the various kinds of meristems in plants.
(iii) State the location and functions of meristems.
Answer:
(i) Meristems are specialized regions of active cell division consisting of immature, living cells that are responsible for plant growth.
(ii) Kinds of meristems: Apical meristem, Intercalary meristem, and Lateral meristem.
(iii) Location and functions:
- Apical meristem: Located at the tips of roots and shoots; increases the length of the plant axis.
- Intercalary meristem: Located between mature tissues (e.g., at leaf bases and internodes of grasses); helps in elongation of organs and regeneration of grazed parts.
- Lateral meristem: Located along the lateral sides of stems and roots (e.g., vascular cambium, cork cambium); responsible for increasing the girth (secondary growth) of the plant.
In simple words: Meristems are plant growth tissues; apical grows length, intercalary grows nodes/leaves, and lateral grows thickness.

Exam Tip: Clearly categorize meristems by position (apical, lateral, intercalary) and origin (primary vs secondary).

Question 27. (i) Suppose you are examining a cross section of a stem under compound microscope, how would you determine whether it is monocot stem or dicot stem?
(ii) Write the characteristics of collenchyma.
Answer:
(i) Differences to distinguish dicot stem from monocot stem:
- Vascular bundles in dicot stems are arranged in a ring, whereas in monocot stems they are scattered throughout the ground tissue.
- Dicot stem vascular bundles are open (with cambium), whereas monocot stem vascular bundles are closed (without cambium).
- Ground tissue in dicot stems is differentiated into cortex, endodermis, pericycle, and pith, whereas in monocot stems it is uniform (undifferentiated).
(ii) Characteristics of collenchyma:
- It consists of living cells with protoplasm.
- Cell walls show localized thickenings due to the deposition of cellulose, hemicellulose, and pectin, especially at the corners where cells meet.
- Intercellular spaces are generally absent.
- It provides mechanical support, tensile strength, and elasticity to young growing organs like petiole and young stem.
In simple words: Ring arrangement and open bundles indicate dicot stem; scattered bundles and uniform ground tissue indicate monocot stem. Collenchyma provides flexible mechanical strength.

Exam Tip: Memorize the key diagnostic features: ring vs scattered vascular bundles is the quickest way to distinguish stems.

Question 28. What is secondary growth in plants? Describe various steps of secondary growth in dicot stem with the help of diagrams.
Answer:
Secondary growth is the increase in the girth (thickness/diameter) of plant stems and roots due to the activity of secondary meristems (vascular cambium and cork cambium).
Steps of secondary growth in a dicot stem:
1. Formation of Cambial Ring: The intrafascicular cambium inside vascular bundles and interfascicular cambium arising from medullary ray cells join together to form a continuous, wavy ring of vascular cambium.
2. Activity of Vascular Cambium: The cambial ring divides actively. Cells cut off towards the inside differentiate into secondary xylem (wood), and cells cut off towards the outside differentiate into secondary phloem. Secondary xylem is produced in much greater quantity than secondary phloem.
3. Spring Wood and Autumn Wood: Cambial activity is dependent on seasonal variations. In spring, cambium is very active, producing lighter-colored spring wood (early wood) with wide vessels. In winter/autumn, cambium is less active, producing darker, denser autumn wood (late wood) with narrow vessels. Alternating concentric rings of spring and autumn wood form annual rings.
4. Formation of Cork Cambium (Phellogen): As the stem expands, the outer cortical and epidermal layers rupture. A new meristem called phellogen (cork cambium) develops in the cortex. Phellogen cuts off cork (phellem) on the outer side and secondary cortex (phelloderm) on the inner side. Together, phellogen, phellem, and phelloderm constitute the periderm.
In simple words: Secondary growth thickens the stem through vascular cambium making wood inside and phloem outside, and cork cambium making protective outer bark.