Effect Of Seed Priming On Emergence, Growth, Yield And In Store Biochemical Changes In Okra Seed

To evaluate the effect of seed priming on emergence, growth, yield and in-store biochemical changes in okra seed, three experiments (laboratory, field and storage) were carried out in 2009-2010. In laboratory experiment, seeds were primed in PEG-8000 (polyethylene glycol) and Mannitol solutions having 0, -0.4, -0.8, -1.2, -1.6, -2 and -2.4 Mpa osmotic potential for 6, 12, 18 and 24 hours duration while dry seeds were used as control. Priming proved effective in improving percent germination (27%) and reducing mean germination time (17.8 h) as compared to unprimed seeds. Priming agents, its osmotic potential and duration significantly affected germination percentage, which increased as osmotic potential lowered from 0 to -1.2 Mpa while further lowering (-1.6 to -2.4 Mpa) osmotic potential adversely affected germination. Similarly germination percentage significantly enhanced as priming duration increased from 6 h to 12 h but further increase in duration from 12 h to 18 h caused insignificant increase in germination percentage. Increase in priming duration beyond 18 h, however, resulted in insignificant decrease in percent germination. Germination was higher for seeds primed with PEG than with Mannitol, but neither priming agent were effective in lowering MGT. MGT reduced significantly as osmotic potential increased from -2.4 to 0 Mpa and duration from 6 h to 24 h. For field experiment, seeds were primed in PEG and Mannitol solutions with same osmotic potentials as used in laboratory experiment. Yields were significantly improved through priming as compared to unprimed seeds. In priming agents PEG primed seeds gave significantly higher yield than Mannitol. Maximum yield was observed at -1.2 Mpa osmotic potential. Priming at high osmotic potential significantly reduced days to 50% emergence, flowering and maturity as compared to unprimed seeds and seeds primed at lower osmotic potential. Minimum days to 50% emergence, flowering and maturity were recorded for plants raised from seeds primed with 0 Mpa osmotic potential. These parameters were not affected by priming agents. On the contrary plant height, AGR (Absolute growth rate) and RGR (Relative growth rate) were affected by osmotic potential of priming solution. Taller plants were recorded at -1.2 Mpa and above this osmotic potential, significantly higher AGR was found in the range of 0 to -1.2 Mpa osmotic potential as compared to other treatments whereas the highest RGR was observed for unprimed seed plots and seed plots treated with lower osmotic potential while less RGR was noted for hydroprimed (0 Mpa) plots. For storage experiment seeds were primed with water, PEG and Mannitol solutions while dry seeds were used as control. After treatment, seeds were dried to initial moisture content (11%) and then evaluated at zero storage, three months and six months storage for their unsaturated fatty acids, hexanal, protein, lipids and electrical conductivity. Results showed reduction in unsaturated fatty acids, proteins and lipids contents and increase in hexanal and electrical conductivity occurred during storage for each treatment but it was significantly controlled by priming with PEG at -1.2 Mpa water potential for 18 hour duration followed by priming with Mannitol at the same water potential and duration as used for PEG priming compared to water treatment and dry seeds