<P> Plants share with animals the problems of obtaining water but, unlike in animals, the loss of water in plants is crucial to create a driving force to move nutrients from the soil to tissues . Certain plants have evolved methods of water conservation . </P> <P> Xerophytes are plants that can survive in dry habitats, such as deserts, and are able to withstand prolonged periods of water shortage . Succulent plants such as the cacti store water in the vacuoles of large parenchyma tissues . Other plants have leaf modifications to reduce water loss, such as needle - shaped leaves, sunken stomata, and thick, waxy cuticles as in the pine . The sand - dune marram grass has rolled leaves with stomata on the inner surface . </P> <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>

The cell must regulate internal concentrations of water