STUDIES ON THE SALT TOLERANCE OF SOME HALOPHYTES IN THE SUDAN

This study is centered on screening the response of Sporobolus spicatus (Vahl) Kunth, Suaeda monoica Forsk. and Zygophyllum album L. to salinity. The plants were subjected to different concentrations of artificial sea water which contains NaCl as the main component. The concentration of artificial sea water ranges between 0.0 - 6.0%. NaCl concentration in the solutions varies between 0.0 - 1026.7 mol m-3. The general growth of the three halophytes relates mainly to salt concentration. The optimum salinity for their development has been established at 0.5 - 1.5% (85.6 - 256.7 mol m-3 NaCl) for Sporobolus spicatus and 0.5 - 1.0% (85.6 - 171.1 mol m-3 NaCl) for Suaeda monoica and Zygophyllum album. Hence, these three species are obligate halophytes. Suboptimal and excessive salt concentrations result in a general decline of the vegetative parameters e.g. fresh and dry weights and crude fibre. Chloride uptake induces salt secretion on the shoot system of Sporobolus spicatus a mechanism to get rid of the excess salt and adjust the plants osmotic pressure, characteristic of a pseudohalophyte. The overall chloride content within the tested plants and precipitated on Sporobolus spicatus tissues is directly proportional to salt concentration. The highest chloride uptake by the three halophytic plants was encountered at 4.5 - 6.0% and the least at the salt-free substrate. The mechanism involved in salt tolerance is based on salt secretion on the shoots of Sporobolus spicatus and succulence in Suaeda monoica and Zygophyllum album i.e. euhalophytes.