ABSTRACT
A study was aimed at standardization of seed dormancy breaking methods and effect of seed priming on germination and field emergence in kalmegh [Andrographis paniculata (Burm. f.) Wall. ex Nees] cv. AK-1. The seeds were subjected to both physical (hot water and sand paper) and chemical scarification (GA3 at 50, 75, 100 and 125 ppm for 15, 30, 45 and 60 min). Among these treatments, seeds treated with 100 ppm GA3 for 15 min exhibited the highest germination percentage (87.55) and seedling vigour. These seeds were then primed using PEG 6000 at osmotic potentials of -0.4, -0.8, -1.2 and -1.6 MPa and GA3 at 50 and 125 ppm. The study revealed that different scarification methods and priming techniques significantly impacted physiological traits such as germination percentage, mean germination time, germination index, time to 50% germination, seedling vigour indices and electrical conductivity. Specifically, seeds osmoprimed at -0.8 MPa at 25 °C for 24 h showed improved germination percentage and seedling vigour, along with reduced mean germination time, time to 50% germination and electrical conductivity. Hence, it was indicated that osmoprimed seeds exhibited superior seed quality attributes as compared to hormoprimed and control seeds Biochemical analyses were carried out to investigate changes in seeds following priming. The results showed that seed priming significantly improved quality of seeds that had undergone dormancy breaking. Enhanced seed viability and vigour was associated with a decrease in highly reactive free radicals, which were neutralized by activity of antioxidant enzymes where in lipid peroxidation marked by the presence of volatile aldehydes and malondialdehyde was reduced by action of superoxide dismutase and catalase enzymes. The study indicated that PEG 6000 treatment with potential of -0.8 MPa at 25 °C for 24 h was more effective in enhancing seed quality compared to other priming methods and potentials.