Question

Explain the lines: In monocotyledons, the leaf base expands into a sheath covering the stem partially or wholly.

Answer 1

In many plants the leaf base expands into a sheath which partially or wholly clasps the stem. This sheathing leaf base is of frequent occurrence among monocotyledons. The sheathing leaf base encloses the stem for some distance above the node Some important examples are Zea mays, sugarcane, wheat, banana etc. In banana, sheathing of many leafs jointly makes a stem like structure known as false stem (pseudostem). True stem of banana is an underground stem.
In some plants, e.g., legumes, tamarind, Mimosa ,mango, banyan, gold- molhur etc., the leaf base becomes distinctly swollen and forms a broadened cushion-like structure, the pulvinus.