Effect of Re-drying Seeds after Wet Treatment at 10°C on the Germination and Growth of Eustoma grandiflorum (Raf.) Shinn

This study was initiated to investigate the effects of wet treatment at 10°C (WT10°C) and subsequent re-drying treatment (RDT) on the germination and growth of Eustoma grandiflorum seeds. Both treatments, WT10°C and RDT, were applied at 10°C under dark conditions. In all the experiments, ‘King of Snow’, which is one of the major Eustoma cultivars in Japan, was used. When the total number of days exposed to WT10°C and RDT was set to 35 days, the prevention of rosettes and the promotion of growth were dependent on the number of days of WT10°C, and these effects were maintained after RDT. When RDT was applied to the seeds after WT10°C for 35 days, the growth promotion due to WT10°C was maintained regardless of the length of re-drying time from 7 to 28 days; however, the germination rate decreased with RDT. On the other hand, applying RDT after WT10°C for 14 days had no effect on the germination rate; however, the growth promotion was insufficient compared with WT10°C for 28 days. This problem was solved by carrying out a further 14 days of WT10°C after RDT. When the seeds were exposed to WT10°C for 14 days, then re-dried for 7 days, and exposed to WT10°C for a further 14 days, the same growth promotion was achieved as for seeds exposed to WT10°C for 28 days continuously. The above results suggest that the promotion of growth depends on the total number of days of WT10°C regardless of whether these days are continuous or not. Moreover, the growth promotion was maintained after RDT. The results also suggest the possibility that when both the processes of WT10°C and the RDT are carried out by seed companies, growers who have no cooling equipment can produce cut flowers using seedlings grown in the high-temperature season.