Q.What are the characteristic features of leaf?

A leaf is a lateral, flattened, green appendage of limited growth that develops from the stem's node and consists of a leaf base, petiole and lamina.

The leaf, as the chief photosynthetic organ, shows several distinguishing characteristic features:

1. Lateral appendage — it develops laterally from the node of the stem, not from the tip.
2. Exogenous origin — leaf primordia arise from the peripheral (surface) region of the shoot apical meristem, unlike lateral roots which arise endogenously.
3. Limited growth — unlike the stem and root, which show unlimited (indeterminate) growth, a leaf has determinate growth; it stops growing once it reaches a certain size.
4. Acropetal development — leaves are produced in acropetal succession (younger leaves nearer the shoot tip, older ones lower down/older).
5. Flattened, dorsiventral structure — typically flattened for maximising light capture, with an upper (adaxial) and lower (abaxial) surface.
6. Axillary bud — bears a bud in the axil (angle between the leaf and the stem), which can develop into a branch or flower. …