The aim of this study was to establish the optimum scarification time for Senna alata seeds in sulfuric acid, as well as to verify the effect of temperature on seed germination for this species under conditions of light and darkness. Seeds were immersed in concentrated sulfuric acid for periods of 0, 15, 30 and 60 minutes, and the germination test was carried out in a BOD chamber at 25ºC, using four replicates of 50 seeds for each time period. Experimental design was completely randomized with 4 treatments. In the second experiment, temperatures from 10 to 45ºC, with 5ºC intervals, were used under conditions of fluorescent white light or continuous darkness (black "gerbox") in order to verify the temperature effect and the most suitable light condition for germination. Experimental design was completely randomized, in an 8x2 factorial arrangement, with 4 replicates of 50 seeds each. In all tests, germination percentage and speed index were daily evaluated for 10 days. Seeds were considered germinated when the radicle length was 2 mm. Data were subjected to analysis of variance and means were compared by Tukey's test at 5% significance. The tegument scarification with sulfuric acid for 60 minutes was optimal for Senna alata seeds since it led to higher values of germination percentage and speed. Germination occurs between 15 and 40ºC, and seeds are considered neutral photoblastic between 20 and 40ºC and negative photoblastic especially at 15ºC. The best germination performance was observed at 25, 30 and 35ºC, at which germination percentage and speed were higher.
"fedegoso-gigante"; germination; dormancy; regime of temperature; photoblastism
