Water in the life of plant:
- about 80 to 95 percent of the plant cells is water.
- about 35-75 percent of the water is present in the wood(sapwood)
- seeds contains 5 to 15 percent of the water.
- to grow and function properly plants cell ever maintain positive water pressure or turgor pressure
- mostly call wall creates internal hydrostatics pressure.
- turgor pressure causes, enlargement of the cell, gaseous exchange in the leaves, make transport through the phloem possible, transport against membrane becomes possible, it provides mechanical support and rigidity and stability to non lignified plant tissues is also because of turgor pressure.
- water passes very easily through the biological membranes. particularly it can pass more easily through aquaporin that are the low resistance pores.
- aquaporins are basically proteins that are embedded in the cell membranes that perform the function of regulation of the water.
- prof Peter Agre discovered these aquaporins.
- large quantity of the water of the plant is lose probably by the process of transpiration. transpiration is define as the process in which water removes from the plant surface through the stomata.
- in one hour 100% exchange of water occur.
- loss of water take place by the plant surface.
- by the process of transpiration process of heat dissipation occurs at the surface of the leaves.
- approximately half of the heat that comes from sun is dissipated by the process of transpiration.
- latent heat of vaporization.
Properties of water:
- cohesion is the basically attraction among the like molecules for example water that gives water tensile strength
- adhesion is the attraction among the unlike molecules like attraction of water molecules with the cell wall, soil particles and it may be with the wall of test tube.
- adhesion property here is explaining the water surface tension and capillarity.
- surface tension is produced by the cohesive force that is within the liquid molecule.
- a phenomenon is caused by the forces is movement of water molecules along a capillary tube and is called capillarity this is also the property of water.
Water as an excellent solvent:
- this is because of the small size of the molecule of the water .
- and because of the polar nature of the water molecule make it good solvent for ionic substances and substance like sugar and proteins that have polar -OH or -NH2 groups.