Protoplasm is the physical basis of life and about 90% of the protoplasm is occupied by water. The activity of protoplasm is stopped due to the want of water. Plants normally use water in various processes including photosynthesis, transpiration, support system and nutrient distribution. Thus water is also named as fluid life.
The necessities of water in plant life are as lotions:
- In keeping, the protoplasm active: The main basis of protoplasm is water. Due to the want of water protoplasm becomes inactive and ultimately dies.
- As the solvent: Water is the best solvent. Prepared food and absorbed mineral salts dissolved in water move from one cell to another and one organ to another of the plant body in the form of the solution.
- As a medium of reaction: Water acts as the only medium for many important metabolic activities.
- As a component of reaction: In many important reactions water is used as a component.
- In preparing food: Photosynthesis does not occur without water and food won’t be formed without photosynthesis. The living world will be ruined if food is not formed. For the production of food in green plants through photosynthesis water is the main raw material.
6CO2 + 12H2O →Light/Chlorophyll→ C6H12O6
- In giving mechanical Support: Often water gives turgidity to cells. Aquatic plants usually have want of turgidity giving tissues. For these plants, water only helps in giving turgidity to cells.
- In the growth of cells: Water is essential for the increase of the volume of protoplasm. The increase in the volume of protoplasm is the precondition for the increase of cells.
- Role of water in germination of seeds: When we sow seeds in soil through imbibition seeds drink water from the soil and swell. The force developed through this activity will break the seed coat and allow the seed to germinate.
- For transpiration: Transpiration is the biochemical process of plants. This process is controlled by water because water plays a key role in closing and opening of stomas and losing of excess water as vapour.
- Role of water in Photosynthesis: Water acts as a source of hydrogen to reduce carbon dioxide to glucose in anabolic chemical reactions of photosynthesis.