Question

Aquatic plants use $C{O_2}$ dissolved in water for:
A.Breakdown of toxic materials
B.Respiration
C.Excretion
D.Photosynthesis

Answer 1

Aquatic plants remain submerged in water and therefore do not have an excess to the gases that are abundantly available in the atmosphere. Therefore aquatic plants utilize the essential gases dissolved in water to carry out their biological processes.

Complete answer:
Aquatic plants have an autotrophic mode of nutrition i.e. they are capable of producing their own food with the aid of biotic components available to them. The green pigment present in plant leaves called chlorophyll helps in the preparation of food.
Aquatic plants intake the carbon dioxide dissolved in water and in the presence of sunshine prepare their food through the process of photosynthesis. The purpose of this biochemical process is to utilize carbon dioxide as a carbon source and prepare glucose which is the simplest form of carbohydrates available. The glucose produced through photosynthesis is used to derive energy for carrying out all biochemical reactions and biological processes inside plants.
The chemical equation for the reaction that takes place during the photosynthesis process can be written as follows:
$C{O_2} + 6{H_2}O\xrightarrow{{photosynthesis}}{C_6}{H_{12}}{O_6} + 6{O_2}$
Therefore, Aquatic plants require carbon dioxide gas for the process of photosynthesis and option (D) is correct.

Note:
The photosynthesis process is a separate process and does not interfere with the respiration process of plants. Plants intake carbon dioxide gas for photosynthesis only and intake oxygen like all other organisms for the process of respiration.