The primordial soup of ancient oceans, from which life originated several billions of years ago on the Earth, had water as the solvent. In a physiologically active cell, more than 90 to 95% of the protoplasm is composed of water. Water is significant to plants and animals for a variety of reasons, some of which are:
- An adequate degree of hydration is essential for the maintenance of physiological processes in a plant cell. The different cell organelles like chloroplasts, mitochondria, etc. require water for maintaining their structure and functions.
- Water is the universal solvent. Most of the biomolecules can dissolve or ionize in water. This property facilitates the absorption of such substances into the plant and also the transport of these substances within the plant in the form of a solution where the solvent is water.
- The turgidity of a plant cell is maintained by the presence of water within the cell.
- The high specific heat of water enables the absorption of large quantities of heat energy with relatively less rise in temperature. This is very advantageous for temperature maintenance at favourable levels in living systems.
- In many plants that grow on land like the Bryophytes and Pteridophytes water is essential for movement of the motile male gametes.
- Hence, water is essential for plants.