DIFFERENTIAL LEVELS OF WHEAT-GERM-AGGLUTININ (WGA) IN GERMINATING EMBRYOS OF DIFFERENT WHEAT CULTIVARS IN RESPONSE TO OSMOTIC-STRESS

The variability in wheat germ agglutinin (WGA) content of germinating embryos of wheat (Triticum aestivum L.) in response to osmotic stress was studied in nine different cultivars with an objective to study its physiological role in stress adaptation. Germination both in water as well as in 0.75 M mannitol resulted in dramatic decrease in WGA conte nt of the germinating embryos as compared to ungerminated ones in all cultivars except PEW-138, PEW-154, and PEW-299. In these three cultiva rs, osmotic stress resulted in a dramatic increase in WGA levels relat ive to ungerminated embryos, thus suggesting that the metabolism of WG A in the germinating wheat embryos of different wheat cultivars is reg ulated differentially by osmotic stress. The specific WGA content of t he ungerminated embryos was substantially higher than the germinating ones, apparently due to increased synthesis of germination associated proteins and increased degradation of WGA in the latter. There was a s trong negative correlation (r=-0.772, significant at P less than or eq ual to 0.001) between germination capacity under stress and stress-ind uced relative increase in the WGA content. Those cultivars which, rela tive to water irrigated seedlings, showed higher levels of WGA per emb ryo in seedlings irrigated with 0.75 M mannitol exhibited lower germin ation capacity. Based on these results, a possible physiological role of WGA in germination of wheat embryos is discussed.