Q21. Pneumatophores are specialized roots found in:
[A] Submerged hydrophytes
[B] Xerophytes
[C] Epiphytes
[D] Mangrove plants
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Correct Answer: [D] Mangrove plants
Explanation: Pneumatophores are specialized, negatively geotropic (growing upwards) roots found in mangrove plants growing in marshy and saline habitats. They help in respiration by providing oxygen to the root system which is submerged in anaerobic mud, having pores called pneumathodes for air intake. Hydrophytes are water plants, xerophytes are desert plants, and epiphytes grow on other plants.
Q22. Stilt roots are adventitious roots that arise from:
[A] Root branches
[B] Nodes of stem
[C] Internodes of stem
[D] Underground stems
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Correct Answer: [B] Nodes of stem
Explanation: Stilt roots are supporting adventitious roots that arise from the lower nodes of the stem, growing obliquely downwards into the soil. They provide additional mechanical support to the plant, common in plants like maize and sugarcane. Prop roots, like in banyan trees, arise from branches.
Q23. Prop roots in banyan trees develop from:
[A] Underground stems
[B] Root branches
[C] Lateral branches
[D] Nodes of stem
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Correct Answer: [C] Lateral branches
Explanation: Prop roots are massive, pillar-like supporting adventitious roots that develop from the horizontal branches of banyan trees (Ficus benghalensis), growing vertically downwards towards the soil. They provide significant mechanical support to the heavy, spreading branches of the tree. Stilt roots are from stem nodes, not branches.
Q24. Which of the following is a modified stem for vegetative propagation and food storage?
[A] Rhizome
[B] Tuber
[C] Bulb
[D] Corm
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Correct Answer: [B] Tuber
Explanation: Tuber, like potato, is a modified underground stem specialized for food storage (starch) and vegetative propagation. It is swollen end of a stem branch, with ‘eyes’ (buds) for new plant development. Rhizomes are horizontal underground stems, bulbs are condensed stems with fleshy leaves, and corms are condensed, solid underground stems – all for storage and propagation but tuber is uniquely swollen end of stem branch.
Q25. Tendrils in cucumber and pumpkin are modified:
[A] Roots
[B] Stems
[C] Leaves
[D] Inflorescences
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Correct Answer: [B] Stems
Explanation: Tendrils in cucumber, pumpkin, gourds and grapevines are slender, spirally coiled structures which are modified stem branches or axillary buds. They help plants to climb by coiling around supports. Leaf tendrils are in peas, stipular tendrils in Smilax, and floral bud tendrils in Passiflora, but in cucurbits, they are stem modifications.
Q26. Thorns of Bougainvillea and Citrus are modified:
[A] Buds
[B] Leaves
[C] Roots
[D] Branches
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Correct Answer: [D] Branches
Q27. Phylloclade is a modification of:
[A] Root
[B] Stem
[C] Leaf
[D] Flower
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Correct Answer: [B] Stem
Explanation: Phylloclade (or cladode) is a flattened or cylindrical green stem modification found in xerophytes like Opuntia (flattene[D] and Euphorbia (cylindrical). It performs photosynthesis, reduces transpiration, and stores water, adapting to arid conditions. Phyllodes are leaf modifications (petiole becoming leaf-like), phyllotaxy is leaf arrangement, phylloplane is leaf surface.
Q28. Bulbils are modified:
[A] Axillary buds
[B] Floral buds
[C] Terminal buds
[D] Adventitious buds
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Correct Answer: [B] Floral buds
Q29. Which of the following is a subterranean stem modified for perennation and vegetative propagation?
[A] Runner
[B] Sucker
[C] Offset
[D] Rhizome
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Correct Answer: [D] Rhizome
Q30. Offset is a type of:
[A] Subaerial stem modification
[B] Underground stem modification
[C] Root modification
[D] Leaf modification
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Correct Answer: [A] Subaerial stem modification