Plant Tissues — Long Answer Questions (Meristematic Tissue)
Medium Level (Application & Explanation)
Q1. What is meristematic tissue? Describe its main characteristics and explain why these features are important for plant growth.
Answer:
Meristematic tissue is a group of undifferentiated cells that can divide repeatedly to form new cells.
Main characteristics:
Undifferentiated cells with no permanent shape or function.
High rate of mitosis, producing new cells continuously.
Cells are small, dense, with thin cell walls and large nuclei.
Tightly packed cells with very little intercellular space.
Importance for plant growth:
Continuous cell division enables primary and secondary growth, increasing length and girth.
Because they are undifferentiated, meristematic cells can differentiate into various specialized tissues (xylem, phloem, epidermis), allowing plants to form leaves, roots and stems.
They help plants repair damage (e.g., after pruning) and are essential for vegetative propagation (cuttings and grafts).
In short, meristematic tissue is the growth engine of plants, supplying new cells and enabling adaptability.
Q2. Explain the role of apical meristem in primary growth. Give examples of how apical meristem activity affects plant form.
Answer:
The apical meristem is located at the tips of roots and shoots and is responsible for primary growth, which increases plant length.
Role and process:
Cells in the apical meristem divide rapidly and then differentiate into tissues such as epidermis, cortex, xylem, and phloem.
In the shoot apical meristem, new leaf primordia and stem tissues are formed, producing branches and leaves.
In the root apical meristem, cells form root cap and root tissues, helping roots grow deeper into soil.
Examples of effects on plant form:
Tall trees and herbaceous plants achieve vertical extension because of active apical meristems.
Formation of new buds and branches occurs near apical regions; removing apical meristem (pruning) often causes lateral branching.
In grasses, apical growth at the tip allows seedlings to reach light quickly.
Thus, apical meristems determine the plant’s height and lengthwise architecture, shaping overall form.
Q3. Describe lateral meristem and how it contributes to secondary growth. Why is secondary growth important for woody plants?
Answer:
Lateral meristem consists of meristematic tissues arranged along the sides of stems and roots; main types are vascular cambium and cork cambium.
Contribution to secondary growth:
Vascular cambium produces secondary xylem (wood) inward and secondary phloem outward, increasing the girth of stems and roots.
Cork cambium forms cork cells outward, replacing the epidermis and forming a protective bark.
Importance for woody plants:
Increased support and strength: thicker stems support larger branches and leaves.
Improved transport: more xylem vessels enhance water and mineral conduction from roots to leaves.
Protection: cork provides insulation, protection from pathogens, and prevents water loss.
Longevity: secondary growth allows trees to live many years by continually adding conducting and supportive tissues.
In summary, lateral meristems enable plants to become woody and robust, supporting height, mass and long-term survival.
Q4. What is intercalary meristem? Explain how it helps grasses and other plants recover after being cut or grazed.
Answer:
Intercalary meristem is located at the base of nodes or leaf bases, especially in grasses and some monocots.
Function and action:
These meristems allow growth between mature tissues (hence “intercalary”), enabling rapid elongation of internodes or leaf bases.
After cutting or grazing, intercalary meristems quickly divide and elongate, regenerating leaves and stem parts.
Examples and significance:
Grass blades regrow from the base because intercalary meristems near the node remain intact when the top is cut.
Lawn grasses and many pasture species rely on this for continuous regrowth, making them highly resilient to mowing and grazing.
Practical benefit:
Farmers and gardeners take advantage of this to harvest fodder or maintain lawns without killing the plant.
Thus, intercalary meristems are key to quick recovery and continued productivity in many plants.
Q5. Compare meristematic tissue with permanent tissue. Explain the significance of this difference for plant development.
Answer:
Comparison:
Meristematic tissue: cells are undifferentiated, small, thin-walled, actively dividing, and have dense cytoplasm and large nuclei. They can differentiate into various cell types.
Permanent tissue: cells are differentiated, specialized for specific functions (e.g., parenchyma, collenchyma, sclerenchyma, xylem, phloem). They usually do not divide further.
Significance for development:
Meristems provide a continuous source of new cells that form different tissues needed for growth and repair. Without meristems, plant growth would stop.
Permanent tissues perform specialized roles like support, storage, photosynthesis and transport; these functions are essential for plant survival and functioning.
The transition from meristematic to permanent tissues allows the plant to grow (via cell division) and then function efficiently (via specialization).
In essence, meristematic tissue is the factory producing new parts, while permanent tissue is the finished product performing life-sustaining roles.
High Complexity (Analytical & Scenario-Based)
Q6. You remove the tip (apical bud) of a young plant. Predict and explain the physiological and developmental changes that follow, mentioning the concept of apical dominance.
Answer:
Prediction: After removing the apical bud, lateral buds below the cut often break dormancy and start growing, producing more branches and a bushier plant.
Explanation and mechanism:
The apical bud produces the hormone auxin (mainly indole-3-acetic acid) that travels down the stem and suppresses growth of lateral buds—this is apical dominance.
When the apical bud is removed, the auxin supply falls, so inhibition on lateral buds is lifted.
Cytokinins produced in roots then act more effectively on lateral buds, promoting cell division and bud outgrowth.
Increased lateral growth changes the plant’s architecture, creating more branches and possibly more leaves and flowers.
Practical use: Gardeners use pruning to control shape and encourage fuller growth. This demonstrates how meristem activity and plant hormones interact to shape development.
Q7. Design a simple experiment to demonstrate that meristematic tissue is responsible for root growth using onion root tips or similar material. Describe steps and expected results.
Answer:
Experimental design (onion root tip):
Take several onion bulbs and allow roots to grow in water for a few days until root tips are visible.
Divide roots into two groups: Control (no treatment) and Treated (apply a mitosis inhibitor like colchicine briefly or gently remove the root tip). If chemicals are not available, cut off the root apical tip in the treated group.
Place roots in suitable water or nutrient medium and observe growth for several days. Record root length daily.
Expected results:
Control roots should continue to grow normally because the root apical meristem is intact.
Treated roots (with tip removed or mitosis inhibited) will show reduced or stopped growth, demonstrating that active cell division in the meristem is necessary for root elongation.
Conclusion: Differences confirm that meristematic cells at the root tip are essential for primary root growth by producing new cells.
Q8. Explain how meristematic tissue enables vegetative propagation from cuttings. What conditions help successful rooting of cuttings?
Answer:
Role of meristematic tissue in cuttings:
When a plant cutting is taken, cells at the cut surface can dedifferentiate and form a mass of meristematic cells called a callus.
These meristematic cells can differentiate into root primordia and new vascular connections, allowing the cutting to develop roots and become an independent plant.
Conditions that help successful rooting:
Healthy cutting material (semi-hardwood or softwood depending on species).
Clean cut and minimal damage to tissues to encourage callus formation.
Moist, aerated medium (sandy soil, perlite) and consistent humidity to prevent desiccation.
Warm temperature and indirect light encourage cell division and root emergence.
Use of rooting hormones (auxins like IBA or NAA) can stimulate root initiation and increase success rate.
Thus, meristematic activity at the wound site is the biological basis of vegetative propagation, aided by proper environmental and hormonal conditions.
Q9. If a tree’s lateral meristem (vascular cambium) is damaged all around the trunk (girdling), analyze the short-term and long-term effects on the tree’s physiology and survival.
Answer:
Short-term effects:
Phloem transport (sugars from leaves to roots) is disrupted because girdling severs the secondary phloem, causing carbohydrates to accumulate above the girdle and not reach roots.
Root systems gradually starve due to lack of food, reducing root growth and function.
Temporary swelling above the girdle may occur due to stored materials.
Long-term effects:
Roots weaken and may die, leading to reduced water an...
