Abstract
Seeds of watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai, cv. Crimson Sweet] were used to investigate the effects of different priming techniques on seed germination and early seedling growth. The seeds were soaked in solutions of 0.2% gibberellin (50 mg L–1 gibberellic acid), 0.2% cytokinin (90 mg L–1 kinetin), 0.2% potassium nitrate (2 g L–1 KNO3), 0.2% calcium nitrate [2 g L–1 Ca(NO3)2] or water (hydropriming) for 6 h at 25°C. After drying, five replicates of 25 seeds were distributed in plastic boxes with blotter paper and kept into a seed germinator at 26°C for 12 days. The different priming treatments significantly affect the measurements of the seed germination and growth of watermelon seedlings. The germination of watermelon seeds ranged from 0 to 100%, and was significantly greater when seeds were subjected to priming with GA3, KNO3, Ca(NO3)2 and water (control), and lower under cytokinin (CK) priming. The seed priming with 0.2% solution of CK resulted in 100% of abnormal seedlings, and therefore should not be used by watermelon growers. Seed priming with GA3, KNO3, Ca(NO3)2 and water (hydropriming) increased the shoot length, whereas GA3, Ca(NO3)2 and water priming improved the radicle length, as well as shoot dry matter watermelon seedlings. The KNO3 and water priming increased the root dry matter of watermelon seedlings. Seed priming with KNO3 and Ca(NO3)2 improved the germination rate and seedling vigor index. The results of this study show that seed priming with GA3, KNO3, Ca(NO3)2 and water (hydropriming) may be useful tools due to their positive effects on germination percentage and growth characteristics of watermelon seedlings. Key words: Citrullus lanatus, cytokinin, gibberellin, hydropriming.
Highlights
Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] is an annual vine of the cucurbit family (Cucurbitaceae)
Seed priming with GA3, KNO3, Ca(NO3)2 and water increased the shoot length, whereas GA3, Ca(NO3)2 and water priming improved the radicle length, as well as shoot dry matter watermelon seedlings
Seed priming with KNO3 and Ca(NO3)2 improved the germination rate and seedling vigor index
Summary
Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] is an annual vine of the cucurbit family (Cucurbitaceae) It is a native species from warm and dry regions of Africa, and widely cultivated throughout. Poor seed germination is a common phenomenon at sub-optimal temperatures (Demir and Mavi, 2004), which causes a great concern for growers that growing watermelon seedlings in late winter and early spring in the southern and south eastern regions of the Brazil. These two regions were responsible for nearly 50% of Brazilian production of watermelon in the 2014/2015 season (AGRIANUAL, 2015). Delayed and reduced seedling emergence cause non-uniform stand establishment, which result in yield reductions (Singh et al, 2001) and impairs the early watermelon markets in the cool regions of Brazil
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