Question

Which of the following aquatic plant does not show pollination by water ?

• A. Vallisneria
• B. Hydrilla
• C. Water hyacinth
• D. Zostera

Answer 1

The Correct Option is C

Pollination by water is known as hydrophily. It is relatively rare in flowering plants, even among aquatic species. We need to determine which of the listed aquatic plants uses a different pollination mechanism. 

• Vallisneria: This is a submerged freshwater plant. It exhibits epihydrophily, where male flowers detach, float to the water surface, and pollinate the female flowers which reach the surface via long stalks. It is pollinated by water.
• Hydrilla: Similar to Vallisneria, Hydrilla is a submerged freshwater plant that also typically uses water for pollination (epihydrophily). It is pollinated by water.
• Water hyacinth (Eichhornia): This is a free-floating aquatic plant. Its flowers are large, colorful, and emerge above the water surface on an inflorescence stalk. These characteristics are typical of plants pollinated by insects (entomophily) or sometimes wind (anemophily). Water hyacinth relies primarily on insect pollinators. It is not pollinated by water.
• Zostera (Seagrass): This is a submerged marine plant. It exhibits hypohydrophily, where pollination occurs entirely underwater. The pollen grains are long and ribbon-like, carried by water currents to the feathery stigmas. It is pollinated by water.

Therefore, the aquatic plant among the options that does not show pollination by water is Water hyacinth.

Answer 2

Vallisneria, Hydrilla, and Zostera are true aquatic plants that exhibit pollination through water (hydrophily).

Water hyacinth, although aquatic, is not pollinated by water. It shows pollination by insects (entomophily). Its flowers emerge above the surface of water, and pollination occurs through biotic agents.

Therefore, the correct answer is: (C) Water hyacinth.