The effects of incorporating plant growth regulators into the priming solution on low temperature germination and emergence performance of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai. cv. Crimson Sweet] seeds were investigated. Seeds were primed in 2.5% (0.25 M) KNO3 solution for 6 d at 25°C in darkness containing one of the following: 1, 3 or 5 µM methyl jasmonate (MeJA), or 1, 3 or 5 mM spermine. Following priming, seeds were subjected to germination and emergence tests at 15°C. Priming watermelon seeds in the presence or absence of plant growth regulators significantly improved germination percentage and rate at 15°C compared to untreated seeds, which failed to germinate. Seeds primed in KNO3 solution containing 1 or 3 µM of MeJA had significantly higher germination percentages, 96 and 85%, respectively, compared to seeds primed in KNO3 only (69%). Germination rate and synchrony were improved by 1 and 3 µM of MeJA added to the priming solution. Emergence was enhanced by priming seeds in the presence of 1 µM (75%) and 3 µM (63%) MeJA compared to seeds primed in KNO3 solution, (35%) while non-primed seeds were unable to emerge at 15°C. Inclusion of spermine at all three concentrations into the priming solution did not significantly improve germination and emergence characteristics of watermelon seeds compared to seeds that were primed in KNO3 solution only. Therefore, priming watermelon seeds in 1 or 3 µM of MeJA incorporated into the KNO3 solution can be used as an effective method to improve low temperature performance of watermelon seeds. Key words: Watermelon, methyl jasmonate, polyamines, germination, emergence.
Effects of Plant Growth Regulators on Low Temperature Induction of Flower Buds in Onion Plants
