Effect of increasing salt concentration on emergence, growth and survival of seedlings of Salvadora oleoides (Salvadoraceae)

Effect of salinization of soil on emergence, growth and physiological attributes of seedlings ofSalvadora oleoides Decne. (Salvadoraceae) was studied. A mixture of chlorides and sulphates of Na, K, Ca and Mg was added to the soil and salinity was maintained at 5•4, 8•1, 10•4, 12•8, 14•7 and 16•5 mΩ−1cm−1. Seed germination exhibited a negative relationship with increasing concentration of salt; however, results further suggested that this tree species is salt tolerant at seed germination stage. Seedlings survived and grew up to soil salinity 16•5 mΩ−1cm−1, which suggests that this species is salt tolerant at seedling stage too. Elongation of stem and root was retarded by increasing salt stress. Roots penetrated moist as well as dry sub-soils to an equal depth. Among the tissues, young roots and stem were most tolerant to salt stress and were successively followed by leaf and old roots. Leaf tissue exhibited maximum reduction in dry mass production in response to increasing salt stress. However, production of young roots was found to be continuous and plants apparently use this process as an avoidance mechanism to remove excess ions and delay onset of ion accumulation in this tissue. This phenomenon, designated ‘fine root turnover’, assumes an importance for the mechanisms of salt tolerance. The ability of this plant to thrive in dry regions is further conferred by the xeromorphic features of its leaves.