Effect of Drought Stress on Seed Embryo Axis Phosphatase Activities During Early Stages of Germination of Two Bread Wheat (Triticum aestivum) Cultivars

Drought resistance is a very important characteristic needed for plant survival especially at germination stage, in arid and semi-arid lands. Phosphatase enzymes are widely found in plants. These enzymes are responsible for dephosphorylation of organic phosphate and altering it to mineral phosphate. Germination experiments were conducted in two bread wheat cultivars (Sardari and Alvand) under simulated drought conditions using different polyethylenglycol concentrations (0, -4, -8, -12, -16 bars). Drought stress decreased germination indices. For assessing phosphatase enzymes activities in drought resistant vs. susceptible cultivars, an experiment was conducted under osmotic conditions with three replications using a completely randomized design. Factors included cultivars, osmotic potentials, and seed imbibition times. Results indicated that drought stress caused the increasing of phosphatase enzymes (acid and alkalin). Also, along with increase in osmotic potential up to -12 bars, phosphatase enzyme activities increased. This increasing enzyme activity was much more pronounced in drought resistance cultivar (Sardari) than the susceptible one (Alvand). Acid and alkalin phosphatase activities in both cultivars (drought resistant and susceptible) increased with increasing seed imbibition time. In this experiment the highest activity for phosphatase enzymes was detected at 18 hours of seed imbibition. However, the activity of acid phosphatase was significantly higher than that for alkalin phosphatase.