Nutrient homeostasis, metabolism of reserves, and seedling vigor as affected by seed priming in coarse rice

The influence of seed priming on germination, seedling vigor, ion homeostasis, and starch metabolism in coarse rice was studied. Priming treatments included pregermination (a traditional soaking method being used for rice nursery preparation), hydropriming for 48 h, osmohardening with KCl or CaCl₂ (ψ -1.25 MPa solution) for 24 h, ascorbate priming (10 mg·L^-1) for 48 h, and hardening for 24 h. Compared with controls, all priming treatments (except pregermination) reduced the time to start germination, improved the rate of germination and synchronization, and the length of shoot and root, seedling fresh and dry mass, number of secondary roots, the concentration of reducing sugars, and α-amylase activity, although the extent of these changes was different in seeds subjected to different treatments. These seed treatments resulted in higher germination that might be due to overcoming dormancy. Osmohardening with KCl was more effective than CaCl₂ for these parameters. Nitrogen concentration remained unaffected in seedlings; however, Ca²⁺ concentrations in both seeds and seedlings were greater in seeds osmohardenerd with CaCl₂ than with all other treatments, including the control. Seed priming enhanced K ⁺ concentration in both seeds and seedlings, leading to improved α-amylase activity. There were positive correlations between seed K ⁺ concentration and amylase activity, and the concentration of reducing sugars with amylase activity, seedling dry mass, or number of secondary roots. Osmohardening with KCl performed better than all other treatments including control. Priming improved the K⁺ balance that activates α-amylase, a basis for seed invigoration.