Effects of Storage Humidity and Germination Temperature on Germination Percentage of Brassica Seeds

Abstract

The present study was conducted to examine the effects of storage humidity and germination temperature on the dormancy and viability of Brassica seeds. Three species of Brassica, i. e., B. japonica. B. cernua and B. napus, were used. Imnlediately after harvest, seeds were stored in five air-tight vessels in each of which relative humidity (RH) of air was settled to be O, 15, 34, 51 and 78% with the aid of varying concentrations of sulfuric acid (H₂S0₄) (Table 1). Germination tests were carried out at five different temperatures, i. e., 5, 15, 25, 35 and 45'C, at one or two week intervals during 8 months in B. japonica, 19 months in B. cernua and 11months in B. napus. Therefore, 25 combinations of storage humidity and germination temperature were made in each species as shown in Figs. 1-3. The optimum storage humidities for the removal of seed dormancy corresponded to 35-50% RH in B. japonica, 15-50% RH in B. cernua and 0-35% RH in B. napus. In these humidities dormancy could be completely removed in 4, 2 and one weeks, respectively, at their own optimum temperatures. In other humidities than the optimum ones, the removal of dormancy was more or less prevented. The preventing effects of desiccation or moistening continued at least until the end of the experiment. It is sometimes said that freshly harvested seeds can germinate only at a limited temperature. However, as the removal of dormancy proceeds, they soon widen the temperature range within which germination can occur. In the present study, seeds, began to germinate at 15'C, which was followed by 25, 35 and 5'C, and Linally at 45'C in every species. When dormancy was removed, seeds could germlnate at all the temperatures, or 45'C. Fig.4 presents one of the examples showing widening of germination temperature ranges.