Optimization of seed hardening techniques for rice seed invigoration

Seed hardening techniques were optimized for vigor enhancement in fine and coarse rice types by evaluating the germination and seedling vigor, and analyzing the electrical conductivity of seed leachates. Seeds were hardened for 12 h (1cycle), 12 h (2cycles), 18 h (1cycle), 18 h (2cycles), 24 h (1 cycle) or 24 h (2 cycles). All the seed treatments resulted in vigor enhancement in both fine and coarse rice types except seeds hardened for 24 h (2 cycles) that behaved similar to that of control. Maximum vigor enhancement as indicated by high germination and seedling vigor, and lower electrical conductivity of seed leachates was noted in seeds hardened for 24 h (1 cycle), which was similar to that of seeds hardened for 12 h (2 cycles) in both rice types.