PLANT PHYSIOLOGY AND BIOCHEMISTRY

Lecture Notes

4. WATER RELATIONS

The Importance of Water for Plants

Class="right">Water, you are beyond description... One cannot say you are

essential for life; you are life itself..., the greatest treasure in the world.

Antoine de Saint-Exupéry.

Water content in plant Tissues typically ranges from 70% to 95%. Due to its unique properties, water plays a pivotal role in all vital physiological processes.

The Significance of water for an Organism is immense, and its Functions are remarkably diverse. Life originated in an aqueous environment, and this environment remains encapsulated within The Cell. All known forms of life on Earth cannot exist without water. When the water content in Cells and Tissues drops to a critical level, living structures enter a state of anabiosis.

Water performs the following essential functions in biological systems:

1. The aqueous environment integrates all PARTS OF THE organism into a single whole (From Molecules to Organs). In plant bodies, the aqueous phase forms a continuous medium, extending from soil moisture all the way to the liquid-gas interface within the leaves.

2. Water serves as a vital solvent and an essential medium for biochemical reactions.

3. It participates in the Organization of Cellular Structures and is an integral component of protein molecules, determining their conformation.

4. Water acts as a metabolite and a direct participant in biochemical processes (as an electron donor in Photosynthesis; it is involved in Respiration, Hydrolysis, and synthesis).

5. Structured water exhibits relatively high proton and electron conductivity.

6. Water is the primary component of the transport system in higher plants.

7. It acts as a thermoregulatory factor.

8. It serves as an effective Shock absorber against mechanical stress.

9. Water maintains the turgor and structural integrity of cells and tissues through the phenomena of osmosis and turgor pressure.

In the course of progressive evolution, plant organisms have become increasingly independent of water.