Abstract
It has been found that a number of temperate forage crops require light on their seed germination. The germination of light-sensitive seeds has been shown to be controlled by reversible phytochrome reaction, in which the photoconversion of the pigment are independent of temperature. However, the germination of such seeds is also apparently dependent on temperature. It is therefore assumed that the mechanism of light-sensitive seed germination is made up of both photoreaction and thermoreaction. The present experiment was carried out to evaluate the interaction of light and temperature eflects on germination of the seeds stored at 10℃ and room temperature of Rumex obtusifolius L. which has been regarded as being temperate herbaceous plant with a typical light-sensitive seed. The results obtained were as follows ; 1) The seeds of Rumex obtusifolius L. could not germinate under continuous dark condition at any constant temperature. 2) Immediately after harvest of mature seeds, the light-dependent germination occurred within a limited temperature range, that is 18℃-20℃. But, with the lapse of the period of dry seed storage at room temperature, the range of germination temperature gradually widened above 20℃. 3) The temperature range permissible for light-dependent germination was increasingly widened by the dry storage at room temperature, but scarecely by the storage at 10℃. The light requirement for germination, however, was not influenced by the dry storage at any temperature. 4) Difference in widening of the temperature range was shown among three seed lots which were collected from different habitats. 5) The time course pattern of the germination under continuous light condition at about 20℃ was invariable during the dry storage of seeds at both 10℃ and room temperature. On the contrary, the time course of the germination at the temperature range higher than 20℃ was hastened corresponding with widening of the temperature range permissible for light-dependent germination as shown in Figure 2.
