Plant Tissues and Anatomy
Solutions
Can you recall? Page No. 85
1. Which component bring about important processes in the living organisms?
Answer: Cells bring about important processes in living organisms.
2. What is tissue?
Answer: A tissue is a group of similar or dissimilar cells with a common function and origin.
3. Explain simple and complex tissue.
Answer: Simple tissues consist of one type of cell performing similar functions (e.g., parenchyma, collenchyma, sclerenchyma), while complex tissues comprise multiple cell types working as a unit (e.g., xylem, phloem).
4. Complete the flow chart.
Organisms → Organs → Cells
Answer: Organism → Organ system → Organs → Tissue system → Tissue → Cells
Can you tell? Page No. 86
1. Enlist the characteristics of meristematic tissue.
Answer: Meristematic tissue consists of young, living, polyhedral cells with thin, elastic cell walls, dense protoplasm, distinct nucleus, high metabolism, and the ability to divide, lacking intercellular spaces.
2. Classify meristematic tissue on the basis of origin.
Answer: Meristematic tissue is classified as primordial (embryonic meristem), primary (from primordial, at root/shoot apices), and secondary (from permanent tissues, e.g., cork cambium).
Can you tell? Page No. 89
1. Write a note on parenchyma.
Answer: Parenchyma is a simple permanent tissue composed of thin-walled, living, isodiametric cells with cellulose walls, prominent nuclei, and large vacuoles. Found in epidermis, cortex, pith, and mesophyll, it stores food and water, aids in photosynthesis, gaseous exchange, and buoyancy, and can dedifferentiate to form vascular and cork cambium during secondary growth.
2. Describe sclerenchyma fibres.
Answer: Sclerenchyma fibres are elongated, narrow, thread-like dead cells with thick, lignified walls and tapering, interlocking ends. They have narrow, unbranched, oblique pits and are arranged in bundles, providing mechanical strength to plant parts like stems and leaves. They are also used commercially in products like jute and hemp.
3. Sketch and label T.S. of phloem tissue.
Answer: The transverse section (T.S.) of phloem tissue includes sieve tubes, companion cells, phloem parenchyma, and phloem fibres. Below is a textual description of the diagram, as direct sketching is not possible in this format:
Description of T.S. of Phloem Tissue Diagram:
- Sieve tubes: Long, tubular cells with sieve plates (perforated end walls) for food conduction.
- Companion cells: Narrow, living cells with dense cytoplasm and nuclei, connected to sieve tubes.
- Phloem parenchyma: Living, elongated cells for storing food and lateral conduction.
- Phloem fibres: Dead, lignified cells providing mechanical support.
- Ground tissue: Surrounding tissue for context.
Labelled Components: Sieve tube, sieve plate, companion cell, nucleus of companion cell, phloem parenchyma, phloem fibre, ground tissue.
Can you tell? Page No. 92
1. Concentric vascular bundles are always closed. Describe.
Answer: Concentric vascular bundles have one tissue (xylem or phloem) completely encircling the other, either as hadrocentric (xylem surrounds phloem) or leptocentric (phloem surrounds xylem). They lack cambium, making them closed, as no secondary growth occurs. This arrangement is typical in certain plants for efficient conduction.
2. How is the arrangement of vascular bundles in dicot and monocot stem?
Answer: In dicot stems, vascular bundles are conjoint, collateral, open, and arranged in a ring, with xylem inside and phloem outside, separated by cambium. In monocot stems, vascular bundles are conjoint, collateral, closed, and scattered throughout the ground tissue, without cambium. This difference affects secondary growth, present in dicots but absent in monocots.
3. How is the structure of vascular bundles of the root?
Answer: Root vascular bundles are radial, with xylem and phloem arranged alternately on separate radii in the stele. Xylem is exarch (protoxylem towards periphery, metaxylem towards center), and the number of xylem/phloem groups varies (diarch to hexarch in dicots, polyarch in monocots). A parenchymatous conjunctive tissue lies between xylem and phloem.
4. Why vascular bundles of dicot stem are described as conjoint collateral and open?
Answer: Dicot stem vascular bundles are conjoint because xylem and phloem are on the same radius, collateral as phloem is outside xylem, and open due to the presence of cambium between them. The cambium allows secondary growth by producing secondary xylem and phloem. This arrangement supports both conduction and girth increase in dicots.
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