The aim of this study was to investigate the influence of different temperatures on the photoblastic response and water uptake of Leonurus sibiricus L. seeds. This medicinal species is from India and has been distributed over Asia, Africa and America, where it is used in the treatment of rheumatic, dermatological and respiratory disorders. Thus, seeds were subjected to temperatures between 5 and 40ºC, at 5ºC intervals, and 20/30, 20/25 and 25/30ºC alternate temperatures, with five replicates of 50 seeds each, under light and dark conditions. In the study of water uptake, seeds were allowed to germinate at 20ºC under light and weighed throughout the germinative process until radicle protrusion. The highest germination percentage and speed index were detected at 20ºC constant temperature and at 20/25, 25/30 and 25/30ºC alternate temperatures under light. There was germination at 10ºC (minimum temperature) and at 40ºC (maximum temperature). The study on water uptake showed that seeds began radicle protrusion at 65h exposure and follow the triphasic pattern in the uptake curve. The statistical model fit for the species was y = 1.869 (1 - 0.414 exp (-0.201 t) + exp [-2.397 + 0.037 (t - 65)], R² = 0.9998.
Photoblastism; medicinal plants; germinative behavior; water content
