Effect of salinization of soil on emergence, growth and survival of seedlings of Cordia rothii

Effects of salinization of soil on emergence, growth and physiological attributes of seedlings of Cordia rothii Roem. and Schult. (Ehretiaceae) were studied. A mixture of chlorides and sulfates of Na, K, Ca and Mg was added to the soil and salinity was maintained at 4.8, 6.2, 8.1, 10.6 and 12.0 dS m(-1). A negative relationship between percent seed germination and salt concentration was obtained. Seedlings did not emerge when soil salinity exceeded 10.6 dS m(-1). Results suggested that this tree species is salt tolerant at the seed germination stage. Seedlings survived and grew up to soil salinity of 10.6 dS m(-1) and eventually this species is salt tolerant at the seedling stage too. Elongation of stem and root was retarded by increasing salt stress. However, this species has a tendency for rapid root penetration and roots are able to extract water from very dry saline soil (6.8% moisture). Among the tissues, young roots and stem were most tolerant to salt stress and were followed by leaf and old roots successively. Production of young roots and death of old roots were 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 to 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. 2002 Elsevier Science B.V. All rights reserved.