<P> Hydrophytes are plants in water habitats . They mostly grow in water or in wet or damp places . In these plants the water absorption occur through the whole surface of the plant, e.g., the water lily . </P> <P> Halophytes are plants living in marshy areas (close to sea). They have to absorb water from such a soil which has higher salt concentration and therefore lower water potential (higher osmotic pressure). Halophytes cope with this situation by activating salts in their roots . As a consequence, the cells of the roots develop lower water potential which brings in water by osmosis . The excess salt can be stored in cells or excreted out from salt glands on leaves . The salt thus secreted by some species help them to trap water vapours from the air, which is absorbed in liquid by leaf cells . Therefore, this is another way of obtaining additional water from air, e.g., glasswort and cord - grass . </P> <P> Mesophytes are plants living in lands of temperate zone, which grow in well - watered soil . They can easily compensate the water lost by transpiration through absorbing water from the soil . To prevent excessive transpiration they have developed a waterproof external covering called cuticle . </P> <P> Kidneys play a very large role in human osmoregulation by regulating the amount of water reabsorbed from glomerular filtrate in kidney tubules, which is controlled by hormones such as antidiuretic hormone (ADH), aldosterone, and angiotensin II . For example, a decrease in water potential is detected by osmoreceptors in the hypothalamus, which stimulates ADH release from the pituitary gland to increase the permeability of the walls of the collecting ducts in the kidneys . Therefore, a large proportion of water is reabsorbed from fluid in the kidneys to prevent too much water from being excreted . </P>

The salt concentration of the body fluids of most vertebrates is