Priming and temperature effects on germination and early seedling growth of someBrassicaspp.

Abstract

Brassica is an important vegetable and oilseed crop. Increased temperature due to climate change may have detrimental effects on Brassica performance. Therefore, seed germination studies were conducted to determine the effect of temperature and hydropriming on germination and seedling growth of Brassica species. Four Brassica species (‘Wang bujang’ (Brassica rapa var. parachinensis), ‘Menang’ (Brassica juncea var. rugosa), hybrid dwarf ‘Pak Choy’ (Brassica rapa var. chinensis), ‘Kailan’ (Brassica oleracea var. alboglabra)) were subjected to priming and no-priming and tested for germination and seedling growth at five temperature regimes of day/night temperatures which included 15/7°C, 20/12°C, 25/17°C, 30/22°C and 35/27°C). The experimental design was a split-plot with temperature as the main-plot and Brassica spp. and priming as sub-plot within the seed germinator chamber. Each temperature was replicated three times. Optimum temperature for seed germination of Brassica spp. was 25°C. Highest seed dry weight was observed in ‘Kailan’ at 35°C (while ‘Wang bujang’ recorded similar dry weight at high and low temperatures). In ‘Menang’ and hybrid ‘Pak Choy’, lower temperatures elicited higher dry weight than high temperatures of 35°C. Priming had no significant effect on germination at 8 days after sowing and seedling dry weight, but mean germination time (MGT) was shorter in hydroprimed seeds than unprimed ones at lower temperature. At 35°C, there was no difference in MGT of hydroprimed and unprimed treatments. Thus, Brassica spp. can survive heat stress at 35°C. The most tolerant species were ‘Kailan’ (B. oleracea var. alboglabra) and ‘Wang bujang’ (B. rapa var. parachinensis). Hydropriming can reduce MGT at lower temperatures.