Guazuma ulmifolia Lam. (Sterculiaceae) is a typical tree species of the initial stages of secondary succession in Brazil, with potential for use in restoring degraded areas. Two experiments were carried out in this work, in which seeds were extracted and scarified before conducting the germination tests. The first experiment was conducted with seeds harvested in October 1995 and aimed to determine the cardinal temperatures for seed germination. Constant temperatures of 10, 15, 20, 25, 30, 35, 40 and 45 ºC were tested under an eight hour photoperiod. The results showed that the minimum temperature is around 10 ºC, the maximum between 35 and 40 ºC, while 25 and 30 ºC temperatures are within the optimum range. The second experiment aimed to evaluate the photoblastic requirement of both freshly harvested (October 1996) and one year dry stored (harvested in October 1995) seeds. Germination tests were conducted at 30 ºC. The results showed that germination of freshly harvested seeds was promoted either by white or by red light, but inhibited by infra-red light or by darkness. Stored seeds, however, were insensitive to light.
forest seed; photoblastism; physiological quality
