There are a lot of plants in this world managed to grow in different kind of environments by adapting to those environments in certain ways. In this essay, plants grow in environment with different salinity are concerned. Plants can be divided into two different groups when it comes to salinity. The first type of plants is the plants that grow and reproduce in saline environment which are called halophytes (Jefferies. 1981). Whereas glycophytes are those plants growing in nonsaline soils (Jefferies. 1981). A saline environment refers to an environment that has high concentration of salt. Sodium chloride often is the dominant salt which present at a concentration of approximately 0.5M in seawater (Jefferies. 1981). There are also other salts such as Na2SO4, MgSO4, CaSO4, MgCl2, KCl, and Na2CO3 may also present in seawater (Jefferies. 1981). The aim of this paper is to investigate the ways of halophytes cope with saline environments which allows them to survive in it.
Effects of saline environment
According to Binzel (1988) (cited by Niu et al. 1995), when plant cells are exposed to salinity, mediated by high concentration of NaCl, kinetic steady states of ion transport for Na+ and Cl- and other ion, such as K+ and Ca2+, are disturbed. High apoplastic levels of Na+ and Cl- alter aqueous and ionic thermodynamic equilibria and therefore resulting in hyperosmotic stress, ionic imbalance, and toxicity (Niu et al. 1995). Besides that, accumulation of salt in the apoplast would also gradually increase the osmotic gradient between inside and outside of the cell (Volkmar et al. 1998). As a result, water inside the call would move outward into the intercellular spaces in order to achieve a thermodynamic equilibrium, leading to progressive cellular dehydration and, eventually, cell death (Volkmar et al. 1998).
Salinity environment affects different parts of the plant. As an example, by McCree (1986) (cited by Volkmar et al. 1998), leaf growth is sensitive to saline solutes even when export and compartmentalization processes are functioning optimally. Volkmar et al. (1998) suggest that the increased salt concentration lowers the osmotic potential of the soil solution and the root zone salinity affects growth by lowering cell turgor. As a result of sudden decreases in turgor pressure, changes are undoubtedly responsible for the inhibition of growth induced by rapid increase in external salute concentration (Volkmar et al. 1998).
The effect of salt on tissue and organ development is reflected in altered patterns of plant growth and development (Volkmar et al. 1998). According to Munns (1988) (cited in Volkmar et al. 1998), continuous exposure of root to salinity progressively decrease leaf size over time. Volkmar et al. (1998) suggested that this affect maybe is a direct effect of salt on rate of cell division, to a slower rate of expansion, or a decrease in duration of expansion. Another effect salinity has on plants are plant ontogeny and shoter time to flowering (Volkmar et al. 1998).
Ways plants cope with salinity environment
Referring to Niu et al. (1995), by comparisons of what have been interpreted to be adaptive responses among various species lead to the conclusion that some salt-tolerant plants have evolved specialized complex mechanisms that allow adaptation to saline stress conditions. Plants adapt to salinity environment in three ways which include osmosis adjustment, ion homoestasis and water permeability.
Polyols refer to chemical compounds containing multiple hydroxyl groups (wikipedia. 2006). According to Bieleski (1982) and Loewus and Dickinson (1982) (cited in Bohnert et al. 1995), accumulation of polyols, either straight-chain metabolites such as mannitol and sorbitol or cyclic polys such as myo-inositol and its methylated derivatives, is correlated to drought or salinity.
Polyols function in two ways...