Effect of ethylene on dormancy-breaking imposed by some environmental factors in Datura stramonium L. seeds

English. The germinative progress of Datura stramonium L. seeds was studied, by submitting it to different temperatures, light and osmotic pressure conditions. Subsequently, the biological activity of ethylene in inducing germinative processes according to various environmental situations was evaluated; a strong activity on dormancy-breaking phenomena, typical of this species, was shown. This plant hormone is active even at the 0.5 ppm (v/v) concentration. Such effect has its saturation level peak between 5 and 10 ppm. The germination trigger is also shown in the case of low temperature and low osmotic pressure. The time of exposure to this substance necessary to stimulate germination processes results to be in inverse proportion to temperature. Both in presence of adverse environmental conditions, of far-red light or low osmotic pressure (-0.6 MPa), a lowering of the efficacy threshold can be observed for this substance, active even at the lowest concentration tested (0.1 ppm). Finally, under extreme conditions of osmotic stress (-0.7 MPa), an additive effect can be observed by submitting seeds simultaneously to ethylene and red light, pointing out a complementary activity. The hypothesis was also put forward of utilizing the plant hormone as a germination stimulator of the seed bank present in the soil, in the attempt of diminishing natural reserves of potential infestation

Italian. E' stato studiato l'andamento germinativo dei semi di Datura stramonium L. sottoposti a diverse condizioni di temperatura, luce e pressione osmotica. E' stata poi valutata l'attivita' biologica dell'etilene nell'induzione dei processi germinativi alle varie situazioni ambientali. Essa ha manifestato una spiccata attivita' nella rimozione dei fenomeni di dormienza tipici di questa specie. Questo ormone vegetale risulta attivo gia' alla concentrazione di 0.5 ppm (v/v). Tale effetto raggiunge il livello di saturazione tra le 5 e le 10 ppm. Lo stimolo germinativo permane anche in concomitanza di basse temperature e pressione osmotica. La durata di esposizione a questa sostanza, necessaria per stimolare i processi germinativi, risulta inversamente proporzionale alla temperatura. In presenza di condizioni ambientali sfavorevoli come in presenza di luce rosso-lontana o di bassa pressione osmotica (-0.6 MPa) si assiste ad un abbassamento della soglia di efficacia di questa sostanza, attiva gia' alla minore concentrazione saggiata (0.1 ppm)