Effects of proline and glycinebetaine on Vicia faba responses to salt stress

Plants of bean (Vicia faba L, cv, Calvor 103) were salt-stressed with NaCl and CaCl2 in concentrations inducing soil osmotic potentials (psi(soil)) from 0 to -1.2 MPa and were sprayed with proline (8.7 mu M) and glycinebetaine (8.5 mu M) solutions. Bean plants respond to increasing soil salinity by decreased leaf relative water content and osmotic potential. Salinity decreased the contents of dry mass, chlorophyll, soluble and hydrolysable sugars, soluble proteins and enhanced content of total free amino acids, Na+, Ca2+ and Cl-. The ratio of K+/Na+ was decreased on salinization. The membranes of leaf discs from salt-stressed plants appeared to be less stable under heat stress (51 degrees C) than that of unstressed plants, The reverse was true for discs placed under dehydration stress (40 % polyethylene glycol 6000). Proline and glycinebetaine application reduced membrane injury, improved K+ uptake and growth. Also both solutes increased chlorophyll contents.