Inhibition of Rumex crispus L. seed germination under natural solar radiation conditions

Abstract

Inhibition of germination by solar radiation is a reaction of phytochrome mechanism, called High Irradiance Response (HIR). Depending on their response to light, seeds are usually divided into three groups: photoblastic positive (germinating in light, but not germinating in darkness), photoblastic negative (giving opposite response) and indifferent (germinating both in light and darkness). The division is based on studies conducted in laboratory conditions, where low irradiance was used. The aim of manuscript is to learn the reaction of Rumex crispus L. seeds, belonging to the group of positive photoblastic seeds, to solar radiation under natural radiation conditions. It was found that the response of seeds depended on the fluence rate of solar radiation. Relations between germination and irradiance, photoperiod, and temperature were described using the stepwise regression method. Under high radiation, germination of photoblastic positive seeds of R. crispus L. was inhibited, and so these seeds behaved as photoblastic negative that do not germinate in the light. In the high radiation conditions, seeds of R. crispus exhibited short-day reactions. A model well describing of changes in three basic factors shaping the germination of R. crispus L. seeds was obtained. These studies in the natural conditions of solar radiation present the ecological significance of these reactions.