Question

Which gas is important for the plant's growth?

Answer 1

Growth of a plant occurs when the cells divide and grow. The most important process that takes place in the plant is photosynthesis. It is the mechanism by which plants make their own food during the day time. Photosynthesis aids in the development of the plant.

Complete answer:
Gases like carbon-di-oxide, nitrogen and oxygen are imperative for the proper functioning of the plant. However, the gas which is the most important for the growth of plants is carbon-di-oxide.
Carbon-di-oxide is the main reactant in photosynthesis. It combines with water from the soil to manufacture Glucose and oxygen. Glucose is crucial for the sustenance of plant life whereas oxygen is required by the plant for respiration. Oxygen is also essential for the respiration of humans and animals.
The Photosynthetic reaction is as follows:
$6C{{O}_{2}}+6{{H}_{2}}O\to {{C}_{6}}{{H}_{12}}{{O}_{6}}+6{{O}_{2}}$
This process is mainly driven by carbon-di-oxide. Because it forms sugar or carbohydrate which has a major component of carbon that comes from carbon-di-oxide. This is the most used gas by the plant as the plant can directly absorb it from the air through the stomata.

Note:
Apart from $CO_2$ , Nitrogen and oxygen are needed by the plant cells for growth. Nitrogen is abundantly present in the atmosphere. But the plant cannot use nitrogen directly from the ait, it has to be fixed by bacteria in order to be utilised by the plant. Certain symbiotic bacteria fix nitrogen in the roots of the plant. This way the plant is always rich in nitrogen and a rich source of protein as it has 16% nitrogen. Also, oxygen is necessary for the plant during respiration at night.