Enhancement of germination and growth of direct-seeded rice through seed priming

A screenhouse study to prove that seed priming can increase the weed suppressive ability of rice through the improvement of early emergence and growth of rice was conducted. Seed priming with 2% KNO3, 2% CaCl2, 2% NaCl and 2% KCl increased the aboveground biomass of rice, while reductions in weed biomass were observed. Seed priming with 100 ppm of GA3, 2% KNO3, 2% KCl, 2% CaCl2, 2% NaCl, and water for 24 h and 48 h improved shoot development and increased total plant biomass under laboratory condition. Seed priming with water for 24 h and 48 h, 2% KNO3, 2% CaCl2, 2% NaCl, and 2% KCl using Mestiso 21, IR64, and NSIC Rc222 rice varieties improved the plant height, number of leaves, tillers and rice biomass, specifically in Mestiso 21 and IR64. With IR64, seed priming with 2% CaCl2, was found to be the best treatment in terms of biomass accumulation. On the other hand seed priming with water for 24 h and 2% KCl in Mestiso 21, and water for 48 h, 2% NaCl and 2% KNO3, in NSIC Rc222 were the best treatments in terms of seedling biomass accumulation. Hence, specificity of seed priming treatments among rice varieties was observed. Interaction of seed priming treatments with seed burial depths in soil revealed that, emergence percentage, tillers, plant survival, and biomass were reduced, while specific leaf area (SLA) relatively increased at 3 cm burial depth compared to 1 and 2 cm burial depths. Within 1-3 cm burial depths, seeds primed with 2% KNO3 CaCI2 produced the highest shoot and total biomass in rice seedlings, promoted early emergence, improved emergence percentage, germination index (GI), and tillering, but reduced the mean germination time (MGT). Other seed priming treatments that were found to be effective based on the above parameters were seed priming with 2% KCI, water for 24 h and 48 h and 2% NaCl. Generally, the hormones (growth regulators) used increased the emergence rate, but reduced the MGT of seedlings at 14 days after sowing (DAS). Taller seedlings were observed in the treatment using gibberellic acid (GA3) and kinetin. Seeds primed with 25, 50 and 100 ppm kinetin and 25 ppm GA3 improved the total aboveground and total rice seedling biomass (+ root), and leaf area (LA). Seed priming with 50 ppm GA3, and 100 ppm GA + Km improved the total aboveground and total rice biomass. Hormonal priming with 100 ppm kinetin was the best seed priming treatment, wherein seedling emergence and vigor production of leaves, and biomass accumulation were enhanced with the early stages of rice growth up to the tillering stage.