The effect of priming treatments on the performance of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) seeds under temperature and osmotic stress

Abstract

Watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) seeds were subjected to osmoconditioning (2% KNO 3 , 20°C, 6 d) or hydropriming (30°C, 18 h) and incubated at 15, 25 and 38°C. Mean time to germination was decreased and germination increased by both priming treatments at 15°C with osmoconditioning being superior to hydropriming. However, neither osmoconditioning nor hydropriming treatment affected germination significantly at 25 and 38°C. The effect of priming on root growth and on emergence from deep plantings was also assessed after synchronisation of radicle emergence between treatments to exclude the confounding effect of germination rate differences. Root growth was not significantly improved by priming but emergence at 15°C was enhanced. It can be concluded from this result that improved emergence after priming is not due to the beneficial effect on radicle emergence only, but also to improved hypocotyl growth. Osmoconditioning increased germination under osmotic stress.