Improvement of plants salt tolerance by exogenous application of amino acids

The present work has been performed to study the growth and metabolic activities of maize and broad bean plants which are shown to have a degree of sensitivity to salinity and to determine the role of amino acids proline or phenylalanine in increasing the salt tolerance of theses plants. Dry mass, water content, leaf area and photosynthetic pigment of maize and broad bean plants decreased with increasing salinity. These changes were accompanied with a drop in the contents of soluble sugars, soluble proteins and amino acids. This was accompanied by a marked increase in the proline content. When maize and broad bean plants sprayed with proline or phenylalanine the opposite effect was occurred, saccharides as well as proteins progressively increased at all sanitization levels and proline concentration significantly declined. Salinity significantly increased the sodium content in both shoots and roots of maize and broad bean plants, while a decline in the accumulation of K+, Ca++, Mg++and P was observed. Amino acids treatments markedly altered the selectivity of Na+, K+, Ca++ and P in both maize and broad bean plants. Spraying with any of either proline or phenylalanine restricted Na+ uptake and enhanced the uptake of K+, K+/Na+  ratio, Ca++ and P selectivity in maize and broad bean plants.   Key words: Proline, phenylalanine, spraying, salinity, maize, broad bean.