The role of the seed coat in the light sensivity in Raphanus sativus L. cv. redondo gigante seeds

The role of the seed coat in the light sensitivity of seeds of Raphanus sativus L. cv. redondo gigante was analysed by germination tests of intact and naked seeds. Far-red light caused high inhibition of seed germination, while under white and red lights low inhibition was found. Naked seeds presented no light sensitivity with high percentage germination under light and darkness. However, incubation of naked seeds in -0.6MPa polyethylene glycol solution resulted in light inhibition as observed in intact seeds. The analysis of the seed coat transmitted light indicated that the filtered light presented the same photoequilibrium of phytochrome when compared to the white light, with a decrease of only 33% in the light irradiance which reaches the embryo

Pelletization of seeds of Raphanus sativus L. cv. Redondo Gigante with graphite for germination under water stress conditions

The effect of water stress on germination of radish seeds is dependent on the presence of light. The effect of pelletization of radish seeds with powdered graphite on the tolerance to water stress under light was analysed. White light and far-red lights were filtered by graphite increasing slightly the tolerance of pelleted seeds to water stress of -0.77MPa. Although red light also inhibited seed germination the graphite had no effect. We propose the pelletization of seeds of Raphanus sativus, at least in cv redondo gigante with graphite as a pratice before planting to increase the tolerance to water stress.<br>O efeito do estresse hídrico é dependente da presença de luz em sementes de rabanete. O efeito da peletização com grafite em pó foi analisado. Luz branca e vermelho-extremo são filtradas pelo grafite aumentando parcialmente a tolerância ao estresse hídrico de -0,77MPa em sementes peletizadas. Embora a luz vermelha também iniba a germinação em condições de estresse a peletização não teve efeito. Nós propomos a peletização de sementes de Raphanus saivus L. cv. redondo gigante como uma prática antes do plantio para aumentar a tolerância ao estresse hídrico