Biology · Ch 9 — Morphology of Flowering Plants
Modification of Leaves
Modification of Leaves
Apart from photosynthesis, the leaf also carries out transpiration, gaseous exchange and the perception of light that triggers flowering. To perform other specialised functions, leaves may undergo the following modifications:
a. Leaf spines — sometimes the entire leaf is modified into a spine (Opuntia), or the margin of the leaf becomes spiny (Agave), or a stipule modifies into a spine (Acacia), in order to check the rate of transpiration or to protect the plant from grazing animals, e.g. Zizyphus.
b. Leaf tendril — in some weak-stemmed plants, for additional support, the whole leaf, a single leaflet, or another leaf part modifies into a thin, green, wiry, coiled structure called a leaf tendril, which helps the plant climb. This can occur as a whole-leaf tendril (e.g. Lathyrus), a leaflet tendril (e.g. Pisum sativum), a leaf-tip tendril where only the extended leaf apex coils (e.g. Gloriosa), or a stipular tendril where the stipules themselves form the tendril (e.g. Smilax).
c. Leaf hooks — in plants such as Bignonia unguis-cati (cat's nail), the terminal leaflets are modified into three stiff, curved, pointed hooks that the plant uses to cling onto tree bark. …
What this figure shows. A cactus pad (Opuntia) with its leaves entirely reduced to sharp spines projecting from small cushion-like points on the stem surface. Reducing the whole leaf to a spine like this cuts down the surface area available for water loss, checking the rate of transpiration, and also protects the fleshy stem from grazing animals -- other plants achieve a similar effect by converting only the leaf …
What this figure shows. Two climbing plants shown side by side: Lathyrus with its entire leaf modified into a coiled, wiry tendril, and Pisum sativum (Pea) with only its terminal leaflets modified into tendrils while the lower leaflets rem …
What this figure shows. A Bignonia unguis-cati (commonly called Cat's nail) shoot with its terminal leaflets modified into three stiff, curved, claw-like hooks used to grip onto tree bark. This modification lets a plant with a naturally weak stem climb over a support by hooking onto it as it grows, much as a l …
What this figure shows. An Acacia auriculiformis branch on which the true bipinnately compound leaf has fallen away and the flattened petiole itself has broadened into a green, leaf-shaped structure carrying …