Question Bank [2022] — BIOLOGY STD 12 Science — Question

Two types of hydrophily:

i. Hypohydrophily:

1. In this pollination occurs below the surface of the water.
2. Here the pollen grains are heavier than water, thus they sink down and caught by stigmas of female flowers.
3. For e.g. In Zostera (sea grass) the pollen grains are long, ribbon-like, and without exine.

ii. Epihydrophily:

1. In this pollination occurs on the surface of the water.
2. The pollen grains float on the water surface and reach the stigma of the female flower.
3. Vallisneria is a submerged dioecious, fresh water aquatic plant. In this, female flowers reach the water surface temporarily to ensure pollination and male flowers float on the surface of the water.
4. The specific gravity of these pollen grains is equal to that of water. Due to which they float on the surface of the water.
5. Due to water currents, pollen grains are carried to stigma and pollination occurs.