COMPARATIVE SALT RESPONSES OF CALLUS-CULTURES OF VIGNA-RADIATA (L) WILCZEK TO VARIOUS OSMOTIC AND IONIC STRESSES

Leaf derived callus cultures of Vigna radiata (L.) Wilczek cv. K-851 were grown on modified PC-L2 medium salinized with various concentrations of NaCl, KCl, Na2SO4 or their mixture and mannitol to study the effect of osmotic and different types of salt stresses on callus growth and ion accumulation. The callus responded differently with stress and salt types. Callus growth was inhibited more severely with Na2SO4, followed by KCl, salt mixture, NaCl and mannitol. A correlation between growth inhibition and the concentration of inorganic solutes in callus tissue was noted. Accumulation of Na+ in callus was accompanied by loss of K+ at all levels of Na2SO4, NaCl and salt mixture. Severe inhibition of cell growth with Na2SO4 was due to more uptake of Na+ by cells under Na2SO4 medium than any other salt and their mixture. SO4-2 ion content in Na2SO4 grown callus was 60-70 times higher than Na+. Similarly, K+ and Cl- contents of KCl callus were greater than Na+ and Cl- of NaCl grown callus. A comparison between salt mixture and its constituent different salts shows that some single salts (Na2SO4 and KCl) were more toxic than a salt mixture. An increase in the osmotic stress (by mannitol) inhibited callus growth less severely than any of the salts. This may be due to higher K+ content of the cells under mannitol stress than iso-osmotic concentration of any of the salts.