PHOTOCONTROL AND TEMPERATURE DEPENDENCE OF GERMINATION OF RUMEX SEEDS

Abstract

1. Light is not obligatory for the germination of the seed of Rumex obtusifolius L. subsp.agrestis DANSER, which has been regarded as being a typical light sensitive seed. Even in continuous darkness, a short period of high (30°) or low temperature (5°) treatment evokes germination very readily. 2. Germination is markedly promoted by 1 min exposure to a red light and this red light effect is completely removed by 1-hr exposure to a far-red light. Alternations of the red and far-red radiation bring about an alternate promotion and inhihibition of germination. 3. When a dark interval is inserted between the red and the far-red treatments, inhibition of germination becomes less distinct as the duration of darkness increases. When the seeds are irradiated with far-red prior to red, with an inserted darkness, germination promotion due to the red light also decreases with the duration of inserted darkness. 4. Complicated interdependence between the light and temperature effects are demonstrated. This suggests a participation of some reactants besides pigments in the photoreaction. 5. The observed interdependence between the light and temperature effects on the germination of Rumex seeds implies that, if, as BORTHWICK has assumed, two forms of pigment, viz., a far-red-absorbing form and a red-absorbing one, are participating in the photoreaction, they should be presumed to coexist from the start of imbibition.