Plant-Water Relation

Importance of Water in Plants

Essential for all physiological activities of the plant.
Main component of plant cells, constituting about 70% by weight in most life forms.
Water content varies among different plants:
- Watermelon: 92% water.
- Herbaceous plants: 10-15% dry weight.
- Carrot root: 85% water.
- Young leaves of lichus: 90% water.

Varies within different parts:
- Woody parts: relatively low water content.
- Other parts: primarily contain water.
Seeds may appear dry but contain water necessary for life.

Medium for Diffusion: Facilitates diffusion of solutes within plant cells.
Solvent: Acts as a solvent for mineral nutrients, enabling uptake from soil and transportation throughout the plant.
Biochemical Reactions: Many biochemical reactions occur in water.
Turgidity: Provides turgidity to plant cells.
Mechanical Support: Offers rigidity and support to plant structures.
Plant Movements: Facilitates movements such as:
- Folding of leaflets in sensitive plants.
- Opening and closing of flowers.
- Stomatal movements in leaves.
Growth: Elongation and growth of plants depend on water availability.
Photosynthesis: Source of oxygen produced during photosynthesis.
Temperature Regulation: Regulates heat within the plant body.
Fertilization Medium: Aids in the dissemination of spores, fruits, and seeds.

Terrestrial plants absorb large amounts of water daily, primarily through transpiration:
- Transpiration: Water loss from leaves to the atmosphere.
- Example: A mature corn plant absorbs approximately 3 liters of water daily; mustard plant absorbs water equal to its weight in about 5 hours.

Due to the high demand for water, it often becomes a limiting factor for plant growth and productivity in both agricultural and natural environments.