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A Handbook of Biology

Thorns: Woody, straight and pointed structures developed from axillary buds. They

protect plants from browsing animals. E.g. Citrus, Bougainvillea. (NEET 2017)

Phylloclade: It is a green, flattened or fleshy cylindrical stem containing

chlorophyll for photosynthesis. Found in some plants of arid regions. E.g. Opuntia

(flattened stem), Euphorbia (fleshy cylindrical stem). (NEET 2016).

Sucker: The lateral branches that originate from the basal underground part of

the main stem. It grows horizontally beneath the soil and come out obliquely

upward giving rise to leafy shoots. E.g. Banana, pineapple & Chrysanthemum.

Underground stems of grass, strawberry etc. spread to new niches. When older

parts die, new plants are formed.

Stolon: Slender lateral branch that arises from the base of the main axis and after

growing aerially for some time arch downwards to touch the ground. E.g. Mint &

Jasmine.

Offset: It is a lateral branch with short internodes and each node bearing a

rosette of leaves and a tuft of roots . E.g. aquatic plants like Pistia and Eichhornia.

Stem modified

into spine

Bougainvillea sp.

Axillary bud

modified

into tendril

Modification of stem for protection Modification of stem for support

THË LËÅF

It is a lateral, flattened structure

borne on the stem. It develops

at the node and bears a bud in

its axil. The axillary bud later

develops into a branch. Leaves

originate from shoot apical

meristems and are arranged

in an acropetal order. They are

important vegetative organs for photosynthesis

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