Physiology and enzymatic activity of asiatic carrot seeds as affected by invigoration treatments

Various seed enhancement treatments including osmo, hydro and halo.priming were evaluated for their efficiency in improving vigour and uniformity of field emergence in Asiatic carrot (Dacus carota L.) cv. Pusa Kesar. Three seed lots of different season's harvest (1998–99, 1999–2000 & 2000–01) were used in the study. All priming treatments improved speed of germination, vigour and field emergence characters. Both osmopriming using PEG-6000 (−0.5 and −1.0 MPa) and halopriming using KNO₃ (15 and 30 mM) were found to be the best with an average improvement of 38% in speed of germination, 47% in vigour index, 5% in field emergence index and 36% in dry weight of one month old seedlings. Significant correlation between laboratory parameters (germination per cent, speed of germination and vigour indices) and field parameters (field emergence per cent, emergence index and seedling dry weight of one month old seedling) was observed. This can be used to predict the field performance of primed seeds. The interaction between seed lots and priming treatments revealed that aged seeds respond better to priming than fresh seeds with respect to seedling vigour and speed of germination. In three treatments, one each of osmo, halo and hydro priming along with untreated control, biochemical changes due to priming was evaluated. Soluble protein increased marginally by 4.7% in primed seed except in hydroprimed. Volatile aldehyde production that is an indicator of seed deterioration was negligible in osmo and halo primed seeds and reduced by 45% in hydroprimed seed compared to unprimed control. The activities of dehydrogenase (an indicator of seed viability) and peroxidase (free radical scavenging enzyme) increased by 148% and 195% respectively in osmo and halo primed seeds. Therefore, in Asiatic carrot cv. Pusa Kesar, osmopriming by PEG-6000 and halopriming by KNO₃ are useful in enhancing vigour and field emergence characteristics.