Biology · Morphology of Flowering Plants · NEET
In pea the tendril is a LEAF modification. In a compound leaf of pea, the terminal leaflets are changed into thin, coiling tendrils that grab support for climbing. This is different from cucumber and pumpkin, where the tendril comes from an axillary bud and is a STEM tendril. NEET loves testing this exact pair, so remember: pea tendril = leaf, cucumber/grapevine tendril = stem.
A phyllode is a flattened, green, leaf-like PETIOLE (the leaf stalk). It is seen in some Australian species of Acacia. Here the true leaf lamina falls off or stays very small, and the petiole becomes broad and green so it can do photosynthesis in the leaf's place. So the green flat structure you see is not a real leaf blade - it is a modified petiole pretending to be a leaf.
Yes. In cactus and Opuntia the leaves are reduced into hard, pointed spines. Two reasons: (1) spines protect the plant from grazing animals, and (2) with almost no leaf surface, water loss by transpiration is very low, which suits dry deserts. Note the trap: in Opuntia the FLAT green fleshy part is a modified STEM (phylloclade), while the SPINES on it are modified leaves.
The pitcher of Nepenthes (a pitcher plant) is a modified LEAF. The leaf lamina forms the jug-shaped pitcher that traps insects, while the tendril-like part and lid also come from the leaf. NEET 2016 asked which option is NOT a stem modification, and the answer was 'Pitcher of Nepenthes' because it is a leaf modification, not a stem one.
Check the ORIGIN. A leaf tendril forms from a leaf part (whole leaf, leaflet, or leaf apex) - examples: pea (leaflets), Gloriosa (leaf tip), sweet pea. A stem tendril forms from an axillary bud or terminal bud - examples: cucumber, pumpkin, grapevine, watermelon. If you cannot recall origin, memorise the standard NCERT example lists; NEET questions reuse the same plant names.
Stems modified into flat green organs performing the functions of leaves are known as:
Identify the correct set of statements: (a) The leaflets are modified into pointed hard thorns in Citrus and Bougainvillea (b) Axillary buds form slender and spirally coiled tendrils in cucumber and pumpkin (c) Stem is flattened and fleshy in Opuntia and modified to perform the function of leaves (d) Rhizophora shows vertically upward growing roots that help to get oxygen for respiration (e) Sub-aerially growing stems in grasses and strawberry help in vegetative propagation.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Tendrils (for climbing, e.g. pea, Gloriosa), spines (for protection and less water loss, e.g. cactus, Opuntia), and phyllode (a flat green petiole doing photosynthesis, e.g. Australian Acacia). The Nepenthes pitcher is also a well-tested leaf modification for insect trapping.
A spine is a modified LEAF (or leaf part), as in cactus and Opuntia. A thorn is a modified STEM (axillary bud), as in Citrus and Bougainvillea. Both are hard and pointed and protect the plant, but their origin is different - this exact difference is a common NEET trap.
A phyllode is a modified LEAF - specifically the petiole (leaf stalk) becomes flat and green to do photosynthesis. It is not a stem. Do not confuse it with a phylloclade, which is a flat green STEM.
Two reasons useful for NEET: spines protect the plant from being eaten by animals, and because there is very little leaf surface, transpiration (water loss) is greatly reduced. Photosynthesis is then done by the green fleshy stem instead.
Leaf tendril: pea (leaflets), Gloriosa (leaf tip), sweet pea. Stem tendril: cucumber, pumpkin, grapevine, watermelon. Origin decides the type - leaf tendrils come from leaf parts, stem tendrils from buds.
