Role and significance of water

Water plays a crucial role in the life of the plant.

Water is called  liquid of life, because life is originated and in the course of evolution.

 It become fully dependent upon water in a number of ways.

Water is one of the most plentiful chemical available in the earth and chemical formula is H2O.

Water molecules consists of an oxygen atom and two hydrogen atom.

oxygen atom is more electronegative than hydrogen tends to attract the electron of the covalent bond.

this attraction result in a partial negative charge at the oxygen in the of the molecule and a partial positive charge at each hydrogen atom.

Water has a special property of solvent which is transported through the body of the plant and animals.

solvent properties is derived from polar structure of the water molecules.

Structure of water molecules.

• Polarity of water molecules give an excellent solvent.
• Hydrogen bonding are due to cohesive and adhesive properties of water.
• Thermal properties of water from hydrogen bonding.
• Polarity of water molecules give rise to hydrogen bond.
  

Importance of water to Plants.

• Plant are water constituent 80 -95% of the mass of growing plant tissue.
• Protoplasm of main constituent is water up to about 90 to 95% of its total weight.
• Water helps in translocation of solutes.
• Elongation phase of cell growth depend on absorption of water.
• Water is directly participate in metabolic reaction.
• Water is increased rate of respiration.
• Water is present in the help in maintaining the turgidity of cells.
• Water is important role of thermal regulation against the high temperature.

Dissociation of water molecules.

Properties of water.

• Solvent for electrolyte and non electrolyte.
• High surface tension
• Tasteless.
• Low viscosity.
• Transparent to visible radiation.
• Highest specific heat.
• Stabilize the high temperature.
• Colour less
• Cohesive and adhesive properties.
• High latent heat of vaporization.

Absorption of water molecules.

Soil water

• Soil is a great reservoir of water for plants.

Gravitational water

Water percolatel downward through larger pores between soil particle under the influence of gravitational force it reached the water table and not available for plant growth.

Hygroscopic water

Water absorb on the soil surface  in the form of tightly held thin-film 

• hygroscopic water are not available for plant growth.

Capillary water

• capillary water available for plants growth.

capillary water fills the space around smaller soil particles and forms the films.

Water table.

• In the depth of soil all  pores are filled with water.

Water absorbing system of the plants.

The main part of the plants which is  water absorbed through the root.

Water absorption through the root, different factor affect the the absorption of water are water, mineral nutrients, Oxygen and temperature.

Absorption of water does not takes palace from the entire surface of root,it  only a young place near the tips are active in absorption of water and mineral substance.

More number of to tips in root favour higher absorption.

Water transport system in plants.

• Xylem tissue

Xylem tissue involve in tracheids ,vessels, xylem fibres, xylem parenchyma.

Mechanism of water absorption in plants.

• Water absorption takes place through root hairs which are in contact with water film on soil particles
• Cell wall of root hairs is permeable membrane.
• Capillary movement of water in soil takes palace through cohesive  force of water.
• Suction pressure is facilitate the water transport system.

• Wall of xylem vessels are inelastic so there is no turgor pressure.
• Water is pushed into xylem vessels by surrounding cortical cells.