Effect of plant growth hormones and abiotic stresses on germination, growth and phosphatase activities in Sorghum bicolor (L.) Moench seeds

Phosphatases are widely found in plants having intracellular and extracellular activities. Phosphatases are believed to be important for phosphorous scavenging and remobilization in plants, but its role in adaptation to abiotic stresses and growth hormones at germination level has not been critically evaluated. To address this issue, the effect of ABA, GA3, NaCl and drought on germination, growth, acid and alkaline phosphatases in sorghum embryos and endosperm was investigated. Germination decreased markedly under ABA, NaCl and drought treatments. Subsequently, a remarkable decrease in fresh weight and dry weight was observed in embryos under ABA and NaCl treatments, whereas a significant decrease in endosperm fresh weight was observed only under drought stress. However, no significant change in endosperm dry weight was observed under other any treatment. Furthermore, a considerable increase in acid phosphatse activity was observed in embryos under GA3 and NaCl treatments, however, alkaline phosphatase activity was substantially higher under all treatments. In endosperm, a significant increase in acid phosphatase activity was observed under ABA and NaCl treatments. Alkaline phosphatse activity was apparently higher under GA3. However, no substantial changes in acid or alkaline phosphatase activities were observed after drought treatments. These findings suggest that changes in the phosphatase enzymes might play important roles in adaptation of germinating seeds, to changing environmental conditions. Based upon these results, a possible physiological role of phosphatases in germinating sorghum seeds is discussed.