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TITLE : PRINCIPLES OF PLANT PHYSIOLOGY.

UNIT:2 1.SOIL AND WATER RELATION, 2.WATER AND ITS ROLE IN PLANT , 3. PROPERTIES AND FUNCTION OF WATER IN THE CELL WATER RELATIONS OF WATER IN CELL WATER RELATION S TERMINOLOGY, 4 WATER POTENTIAL OF PLANT CELL.

1. SOIL AND PLANT WATER RELATION Plants absorb water from soil by their roots . Soil water means water present in soil / Plant absorb water from the soil is by their roots .

DIFFERENT TERMINOLOGY RELATED TO WATER . Holard – The total amount of water present in soil is termed as Holard. Chesard – Available water to plant is called Chesard . And which can’t be avaible to plant is termed as Ehard.

Gravitational water – A part of water percolates downwards through large pores between the soil particles under the influences of gravity and it’s called gravitational. In case the gravitational water is available to the plants it’s absored . A good amount of water is retained by the soil particles and known as FIELD CAPACITY MOITURE.

2. This water present in a three form A. Capillary water- The water present in the intercellular space of soil partical is called capillary water. B. Hygroscopic water- The water which is present around the soil partical in the form of vapour C. Crystelline water OR Chemically combined water- Chemically bound to the soil partical is called as a chemically combined water . Ex. CuSO4, 5 H2O.

3. Water absorbing parts of plant The water required by plant is observed by the roots but absorption of water by leaves and stem has also been found in a few plant Hydrophytes absorb water by general surface Wood (1925) reported that Ikochia bosia and Rhoagidia absorbed water in appreciable amount from atmosphere

WATER AND ITS ROLE IN PLANT Water is terms from the OH-and H+ atom Necessary to plant life required in largest amount Persent throuhout plant body The evaporating surface fo mesophyll cells

PROPERTIES OF WATER IMPORTANT TO LIFE 1.PHYSICAL PROPERTIES WATER A.specific heat: The amount of heat energy required to raise the tempreture of unit mass of substance 1 is called as specific heat .

Latent Heat Of Vaporization. It’s the energy required to convert liquid into gas phase at constant tempature .

Latent Heat Of fusion. It’s the heat energy required to convert to unit mass of solid to a liqid at same tempature.

WATER EXPANSION AND DENSITY –Water has a density to expand as it’s density is decreased therefore ice has lower density water reaches is minimium density.

Cohesive and Adesive properties . The mutual force of attraction between like molecules such as in water it’s called as cohension . Attraction of water to a solid phase such as cell wall or glass surface is called as adesion.

Water as solvent - Variety of subtences can readily in water . Water is especially powarfull solvent for electrolyte and other subtences such as sugar , protins etc.

FUNCTION OF WATER IN PLANTS 1 Major constituent of protoplasm . 90 to 95 percent of it’s weight . 2 Water is solvent in which mineral nutrient s enter a plant from soil solution . 3 In which mineral nutrients are transported from one part of cell to another from cell to cell , tissue to tissue , and organ to organ. place to other place

4 Water is medium in which many metabolic reaction occurs. 5 Water is reactant in a number of metabolic reactions .

6 Water imparts turgidity to growing cell and thus maintains their form and structure . 7 Water provides mechnical support and turgidity to nonlignified plant cell.

8 Elongation phase of cell growth depends on asorpation of water . 9 Water is mtabolic end product of respiration .

10 More water is absorbed by plants and greater amount of water are lost by plants than any other subtances . 11 Water plays very important role of thermal regulation against high tempature .

WATER POTENTIAL In the plant and soil the potential energy of water is called as water potential . The chemical potential of water  free energy per mole. Symbolized the by the greek letter psi w .

Expressed as force per unit area . Unit measurment is usully the Bar / Pascal.

Pure water has water potential equal to 0 bar . Water potential in plants and soil is usully less than 0 bar . Which means it’s negative value. More negative value the lower water potential .

SIGNIFICANCES OF WATER POTENTIAL Lower the water potential in plant cell or tissue the grater it’s ability to absorb water .

Higher the water potential the greter it’s the ability to tissue to supply water to other m ore desicated cells and tissue . Water potential used to measure water deficit and water stress in plant cell tissue. End Show

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