Plant Tissues and Anatomy
Short Questions
1. What is a tissue?
Answer: A group of similar or dissimilar cells with a common function and origin.
2. What is the main function of meristematic tissue?
Answer: To divide and contribute to plant growth.
3. Where is apical meristem located?
Answer: At the tips of roots and shoots.
4. What is the role of intercalary meristem?
Answer: It promotes growth at the base or top of nodes, mainly in monocots.
5. What is a permanent tissue?
Answer: Cells that have lost the ability to divide and have specialized functions.
6. What is the primary function of parenchyma?
Answer: To store food, water, and aid in photosynthesis and gaseous exchange.
7. What distinguishes collenchyma from other tissues?
Answer: It has unevenly thickened cell walls providing mechanical support.
8. What is sclerenchyma composed of?
Answer: Dead cells with lignified walls for mechanical strength.
9. What is the function of xylem?
Answer: To conduct water and minerals and provide mechanical support.
10. What are sieve tubes in phloem?
Answer: Long tubular channels for conducting organic food.
11. What is the epidermal tissue system?
Answer: The outermost protective layer of the plant body.
12. What are stomata?
Answer: Small pores in the epidermis for gas exchange and transpiration.
13. What is a vascular bundle?
Answer: A unit of xylem and phloem for conduction in plants.
14. What is secondary growth in plants?
Answer: Increase in girth due to the activity of vascular and cork cambium.
15. What is heartwood?
Answer: The inner, non-functional, durable part of secondary xylem.
Long Questions
1. Explain the classification of meristematic tissue based on origin.
Answer: Meristematic tissue is classified into primordial (embryonic meristem at root/shoot tips), primary (derived from primordial, forming permanent tissues), and secondary (developed from permanent tissues for lateral growth). Primordial meristem occupies a minute area, primary meristem is present from the beginning at apices, and secondary meristem, like cork cambium, appears later. This classification reflects their developmental roles in plant growth.
2. Describe the characteristics of meristematic tissue.
Answer: Meristematic tissue consists of young, living cells with thin, elastic cell walls and dense protoplasm. These cells are polyhedral, lack intercellular spaces, and have a high metabolic rate with a distinct nucleus. Their primary function is continuous division, contributing to plant growth in specific regions.
3. What are the features of parenchyma tissue?
Answer: Parenchyma cells are thin-walled, living, and isodiametric with large vacuoles and prominent nuclei. They are distributed in cortex, pith, and mesophyll, performing functions like storage, photosynthesis, and gaseous exchange. Their ability to dedifferentiate aids in forming vascular and cork cambium during secondary growth.
4. How does collenchyma provide mechanical support?
Answer: Collenchyma is a living tissue with unevenly thickened cell walls rich in cellulose and pectin, especially at corners. Found in young stems and petioles, it provides flexibility and strength, allowing bending without breaking. Its compact arrangement enhances support in growing plant parts.
5. Explain the structure and function of sclerenchyma.
Answer: Sclerenchyma consists of dead, thick-walled cells with uniform lignin deposition, occurring as fibres (elongated, narrow) or sclereids (broad, blunt-ended). It provides rigidity and mechanical strength to leaves, stems, and seeds. Commercial fibres like jute are derived from sclerenchyma.
6. Describe the components of xylem tissue.
Answer: Xylem comprises tracheids, vessels, xylem parenchyma, and xylem fibres. Tracheids and vessels conduct water and minerals, while fibres provide mechanical support; parenchyma stores food. In angiosperms, vessels are primary conductors, whereas tracheids dominate in gymnosperms.
7. What is the role of phloem in plants?
Answer: Phloem, a living tissue, conducts organic food from leaves (source) to other plant parts (sink). It consists of sieve tubes, companion cells, phloem parenchyma, and fibres. Companion cells regulate sieve tube functions, while fibres provide support.
8. How does the epidermal tissue system function?
Answer: The epidermal tissue system, derived from protoderm, forms the plant’s outer protective layer with a waxy cuticle to prevent water loss. It includes stomata for gas exchange and transpiration, and appendages like trichomes and root hairs for protection and absorption. Guard cells regulate stomatal opening and closing.
9. Explain the types of vascular bundles in plants.
Answer: Vascular bundles are radial (xylem and phloem on separate radii, e.g., roots), conjoint collateral (xylem and phloem on the same radius, e.g., stems), or concentric (one tissue encircles the other, e.g., hadrocentric or leptocentric). Conjoint bundles may be open (with cambium) or closed (without cambium). These arrangements determine conduction and growth patterns.
10. Describe secondary growth in dicot stems.
Answer: Secondary growth in dicot stems involves the formation of a continuous cambial ring from intrafascicular and interfascicular cambium. The cambium produces secondary xylem (inner) and phloem (outer), increasing stem girth. Cork cambium forms periderm, replacing the epidermis and aiding in protection.
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