Salt Stress and Phytohormone (ABA)-Induced Changes in Germination, Sugars and Enzymes of Carbohydrate Metabolism in Sorghum bicolor (L.) Moench Seeds

The effect of NaCl and ABA on germination, sugars and enzymes of carbohydrate metabolism in sorghum embryos and endosperm was investigated. Both phytohormone and salt stress influenced different aspects at physiological and biochemical level. Germination decreased markedly under NaCl and ABA treatments. Subsequently, an influence of salt stress and ABA on total and reducing sugars along with amylase activities and invertase activities was also observed, reflecting the impact of exogenous abiotic treatments on interconversion between carbohydrates and correlating enzymes. There was a considerable increase in the total and reducing sugar content in embryos and endosperm following both treatments. Both αand β-amylase activities were enhanced by salt and ABA treatments, with former (α-) enhanced more than latter, and were significantly correlated with the concentrations of soluble sugars in the embryos and endosperm. In addition, both ABA and NaCl decreased the mobilization of starch, resulting in high starch levels in control embryos and endosperm compared with treated tissues. The reduction in starch content was more under NaCl treatment than ABA, in embryos and endosperm. The other two enzymes, acid-invertase and alkaline-invertase, showed significant enhancement upon both treatments in embryos. On the contrary, in endosperm, only acid-invertase activity was significantly increased, whereas, alkaline-invertase activity was least affected. Based upon all results, a possible physiological role of these sugars along with enzymes of carbohydrate metabolism in germinated sorghum seeds under salt stress and phytohormone ABA is discussed.