Q.(a) Draw the structure of leaf and mark the parts.

A typical leaf is made of leaf base, petiole and lamina; a pulvinus leaf base is swollen and cushion-like (enabling movement, as in Mimosa), while a sheathing leaf base wraps around the stem like a sheath (as in grasses) — described here since a hand-drawn diagram cannot be produced in text.

(a) Structure of a leaf and its parts:

A typical dorsiventral leaf consists of three main parts:

1. Leaf base — the region where the leaf attaches to the stem at the node; may bear a pair of lateral outgrowths called stipules.
2. Petiole — the stalk of the leaf that holds the lamina (blade) out to the light and allows it to move/flutter in air currents.
3. Lamina (leaf blade) — the flat, expanded green part of the leaf, containing:
   • Midrib — the prominent central vein running from base to apex.
   • Veins and veinlets — the branching vascular network (venation) arising from the midrib, either reticulate (net-like, in dicots) or parallel (in monocots).
   • Margin — the outer edge of the lamina, which may be entire, serrate, dentate, etc.
   • Apex — the tip of the lamina.

(b) Pulvinus and sheathing leaf bases (two special modifications of the leaf base):

• Pulvinus leaf base — the leaf base becomes swollen, cushion-like, and pulvinated; it is filled with motor cells whose turgor changes allow rapid or slow movement of the leaf/leaflets. Classic example: Mimosa pudica (touch-me-not), where the pulvinus enables the leaflets to fold rapidly on touch (seismonasty), and many legumes show pulvini enabling daily 'sleep movements' (nyctinasty). …