Priming of Watermelon Seeds for Low-temperature Germination1

Abstract

Abstract Watermelon seeds ( Citrullus lanatus (Thunb.) Matsum. & Nakal cv. Sugar Baby) require high temperatures to germinate successfully. Under light conditions germination is inhibited at 20°C and lower and in the dark below 15°. The cause of the light inhibition at 20° lies in the embryo proper. Imbibition at 0° (up to 10 days) did not cause any apparent damage to the seeds, which germinated freely upon transfer to optimal temperature. Watermelon seeds could be primed for low-temperature germination by pretreatment at 30° or 35° or by imbibing the seeds in salt solutions prior to sowing. Inorganic osmoticum was superior to organic osmoticum. Differences in the efficacy of the priming existed among the different salt solutions tested. The best treatment was 2% or 3% KNO 3 for 6 days. NH 4 NO 3 , NaNO 3 , Ca(NO 3 ) 2 and KC1 had similar effectiveness. After priming, seeds could be kept in dry storage for long periods (checked up to 20 weeks). Emergence studies confirm the effectiveness of the priming treatment for low-temperature germination of winter-grown watermelon.