Effect of salt priming on germination and seedling growth at low temperatures in watermelon seeds during development

Abstract

The effect of salt priming (KNO 3 , 20°C, 3%, 6 d) on germination at seven and 14 days after planting and on root and shoot lengths of watermelon (Citrullus lanatus (Thunb.) Matsum and Nakai) seed lots harvested at a range of intervals from anthesis and at two levels of temperature was investigated during the years 2000 and 2001. Untreated seeds of 15, 20, 25 and 30 DAA (days after anthesis) were unable to germinate and final germination was lower than 20% in subsequent harvests until 60 DAA at 14°C. While at the same temperature treated seeds had germinated as early as 20 DAA and reached to 66% and 51% in 40 (2000) and 35 DAA ( 2001), respectively. Germinated seeds were unable to grow shoots at 14°C in either year. At 18°C, treatment was not effective on germination percentages at day seven in all three lots in 2000 but improved root and shoot lengths. The advantage obtained from the treatment varied among the lots with a minimum benefit of an increase of 15 mm in root and 28 mm in shoot length, respectively. Priming increased germination percentages at day seven and final and root and shoot length of all seed lots in 2001. Germination percentages in treated seeds varied between 68% and 84% in seeds harvested 20 DAA and thereafter. The less mature the seeds the higher the benefit obtained from the treatment. Maximum root and shoot lengths were recorded in seeds of 35 DAA as 37 and 40 mm in the control and as 60 and 61 mm in treated, respectively. We concluded that salt priming can be useful for improving germination, seedling growth and uniformity of heterogeneously matured watermelon lots at low temperatures to produce well developed seedlings in early spring sowings.