Abstract
Seed germination is one of the most critical and complex physiological stages in the plant life cycle. It is highly affected by environmental stress. Priming is a promising tool for the improvement of the plant withstanding against different biotic and abiotic. Most studies that deal with the evaluation of the role of priming on germination evaluate the metabolic and biochemical reactions through germination and not evaluate the enzyme kinetics. From this point of view; this study investigates the effect of the rice grain biopriming with rhizobacteria on amylase properties and its tolerance to metals. The rice grains were divided into two groups the first was hydroprimed as the agricultural instruction mentioned, the second group was bioprimed with Pseudomonas fluorescens suspension. The two groups were germinated for 4 days (complete germination) after that the germination parameters were determined and the amylase enzyme was extracted from the two groups of germinated grains. The effect of different temperature and pH values on the activity of the purified amylase, amylase tolerance to metals and its Km and Vmax were determined. Results showed that biopriming with rhizobacteria can effectively increase the rice grain germination more than the hydropriming. The superior of the biopriming in germination improvement is related to the improvement of amylase properties such as the improvement of its activity under different temperatures and pH values, and its tolerance to metals. Also the biopriming increase the affinity between amylase and substrate with increasing in its maximum velocity (decreasing the Km and increasing the Vmax).