ADAPTIVE COMPONENTS OF SALT TOLERANCE IN SOME GRASSES OF CHOLISTAN DESERT, PAKISTAN

Abstract

Five potential salt tolerant forage grasses (Aeluropus lagopoides, Cymbopogon jwarancusa, Ochthochloa compressa, Lasiurus scindicus and Sporobolus ioclados) were collected from the salt affected habitats of Cholistan desert to assess their adaptive components of salt tolerance to saline stress by determining various morpho-anatomical and physiological attributes. The degree of salt tolerance of the ecotypes of all five grasses from the differentially saline habitats was compared in a hydroponic system. In general, the ecotypes from the highly saline Ladam Sir (LS) habitat of all five grasses performed better under high salinities than their counterparts from the moderately saline Bailahwala Dahar (BD) and least saline Derawar Fort (DF). All these species showed specific adaptive modifications in their structure and physiology as well as definite mechanisms to deal with high salinity levels of external environment. The LS ecotypes of A. lagopoides and O. compressa generally tended to exclude toxic ions through leaves and this salt exclusion mechanism responsible for their successful survival under highest salinity levels. The LS ecotypes of S. ioclados and C. jwarancusa were tolerated moderate salinities and more relied on restricted uptake of toxic ions and succulence while L. scindicus was the sensitive to high salinities and relied more on the accumulation of free amino acids and proline. In conclusion, the present study on the salt tolerance of natural populations of five desert grass species confirms that natural selection had a considerable impact on the development of adaptive components of salt tolerance in these grasses which clearly depict that plant growing in prevailing saline environments must have specific genetic makeup developed as a result of natural selection over long period of time.