OSMOREGULATION CONCEPTS AND ROLE IN PLANTS

                                     OSMOREGULATION

Water relations of cell

Water is the solvent of the solutes in the cell. Each cell has been adapted to a defined quantity of water in relation to salts in it to perform its functions. Homeostatic mechanisms generally maintain this concentration.

Balance of water and solutes in the body:

Cells consistently encounter changing extracellular environment.

Hypotonic Environment:

If external environment is diluted solution compared to the cell concentration it is designated as hypotonic environment. (external)

The hypotonic environment osmotically causes entry of water into the cell and renders the cell solutions diluted. The cell also becomes turgid. Thus it may be harmed.

Hypertonic Environment:

If external environment is more concentrated solution compared to the cell concentration it is designated as hypotonic environment.

Hypertonic environment makes cell solutions concentrated and shrinks the cell due to loss of water.

Isotonic Environment:

If external environment resembles in concentration of solutes to internal solution it is termed as isotonic environment.

To prevent shrinkage or flooding the cells osmoregulate themselves to keep water and salts balance in plants and animals.

                                 OSMOREGULATION IN PLANTS

Plants are distributed in different habitats of aquatic, moderate and severely dry terrestrial nature, thus termed as hydrophytes, mesophytes and xerophytes, respectively.

Xerophytes:

Xerophytes have the adaptations for reduced rate of transpiration. (Habitat= dry, desert)

Characteristics of xerophytes:

1.        Many xerophytes possess small, thick leaves to limit water loss by reducing surface area proportional to the volume.

2.      Their cuticle is thick, waxy and leathery.

3.       These have less number of stomata.

4.      Stomata are on lower surface of leaves and located in depression.

5.      Some as cacti, during the dry season, shed their leaves to restrict transpiration completely, thus stems are the photosynthetic organs.

6.      In rainy season, stem stores water for use in dry conditions. (succulent organs)

7.      These have log roots.

Examples: cactus, euphorbia

Hydrophytes:

 Their habitat is fresh water.

Characteristics of Hydrophytes:

·         Hydrophytes have the adaptations to remove the flooding of its cells in fresh water

·         Surface area of leaves is very large to transpire water excessively.

·         Extensive stomata are present on the upper surface facing the atmosphere to promote loss of water.

Examples: water Lilly, water lettuce

Mesophytes:

These live in moderate water availability.

Characteristics of mesophytes:

·         In sufficient supply of water stomata are kept open to promote loss of excess water

·         In restricted supply stomata close to prevent the loss of water.

Examples: Brassica, rose, mango etc.