Osmopriming, Halopriming and Hormopriming for Improving Seedling Establishment and Vigour in Rice (Oryza sativa L.) under Aerobic Conditions

Seed priming is a pre-sowing technique to improve crop emergence, seedling vigor and stress resilience. In direct-seeded rice (DSR), uneven germination often limits uniform establishment and increases vulnerability to stress. To evaluate effective priming methods for enhancing rice (Oryza sativa L.) seed germination, an experiment was conducted under a completely randomized design (CRD) in the Seed Physiology Laboratory, Punjab Agricultural University, Ludhiana, India. Treatments included control (no priming), hydropriming; osmopriming with PEG 6000 (–0.1, –0.2 and –0.5 MPa); halopriming with sodium selenate (30, 45 and 60 µM), potassium nitrate (50, 100 and 200 mM), calcium chloride (50, 100 and 200 mM) and di-potassium hydrogen phosphate (30, 60 and 120 mM); hormopriming with gibberellic acid (GA3: 50, 100, 200 and 300 µg/mL), benzyl adenine, and ethrel (1, 5, 10 and 20 µg/mL each) and priming with the cell-cycle inhibitor hydroxyurea (5, 10 and 25 mM). Seeds were soaked for 12 h and air-dried. Among treatments, osmopriming with –0.1 MPa PEG 6000, halopriming with 30 µM sodium selenate, 200 mM KNO3, 100 mM CaCl2, and 30 mM K2HPO4, hormopriming with 200–300 µg/mL GA3 and 10 mM hydroxyurea markedly improved germination percentage, speed and vigor indices, while reducing mean germination time and electrical conductivity, reflecting better membrane integrity. Hormopriming with GA3 (300 µg/mL) achieved the highest germination (92.7%), followed by sodium selenate (91.3%) and KNO3 (89.3%), compared with lower values in control and hydropriming. Field emergence was also higher with GA3 (85%), sodium selenate (84%), and KNO3 (82.7%) versus 73% in control (no priming). Thus, seed priming with GA3 (300 µg/mL), sodium selenate (30 µM) or KNO3 (200 mM) can ensure rapid and uniform stand establishment in aerobic rice.