Effect of salinization of soil on growth and macro- and micro-nutrient accumulation in seedlings of Salvadora persica (Salvadoraceae)

Abstract

Effects of salinization of soil on emergence, seedling growth and mineral accumulation of Salvadora persica Linn. (Salvadoraceae) were studied. A mixture of chlorides and sulphates of Na, K, Ca and Mg was added to the soil and salinity was maintained at 4.3, 6.1, 8.4, 10.3, 12.5, 14.9 and 17.2 dS m −1. A negative relationship between seedling emergence and salt concentration was obtained. Seedlings did not emerge when soil salinity exceeded 14.9 dS m −1. Results suggested that this tree species is salt tolerant at seed germination and seedling stages. Elongation of stem and root was retarded by increasing salt stress. Young roots and stem were most tolerant to salt stress and were followed by leaves and old roots. Leaf tissue exhibited maximum reduction in dry mass production in response to increasing salt stress. However, 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” is of an importance to the mechanisms of salt tolerance. Plants accumulated Na in roots and were able to regulate transfer of Na ions to leaves. Stem tissues were barrier for translocation of Na from root to leaf. Moreover, K significantly increased in leaf, but decreased in root tissues with increased salinization. Nitrogen content significantly decreased in all tissues (leaf, stem and root) in response to low water treatment and salinization of soil. Phosphorus content significantly decreased, while Ca increased in leaf as soil salinity increased. Changes in elements accumulation pattern and the possible mechanisms for avoidance of Na toxicity in tissues and organism level are discussed.