Efeito da temperatura sobre a germina??o de três espécies de Pinus cultivadas no Brasil

摘要

The Pinus species present a high level of resistance to forest fires, being considered as active pyrofit plants. For this reason a question is raised: Did the seed behavior of these species develop exclusively due to fire disturbances or by other causes that have influenced this process?, Still, did these species develop similar adaptable answers? To answer these questions, seeds of three species of Pinus species were exposed to different thermal intensities and time of exposition, in order to simulate responses to the different fire regimes, evaluating the effects of high temperatures on the seeds, as well as the effect of ashes, as the most notable element of the micro-environment in which the plants should grow later. The used plant material was acquired from IPEF (Researches and Forest Studies Institute) - Piracicaba, SP. To evaluate seed responses to the temperatures, an entirely randomized statistical design with factorial arrangement was used. In the absence of thermal treatments, the seeds presented high germination rates and strong reduction in temperatures equal or superior to 70 oC, suggesting that they are not really active pyrofit plants. The germination values obtained with temperature equal to 50 oC differed statistically from the control, and when the temperature values were equal or superior to 110 oC, an important germination reduction occurred in all treatments. The simultaneous evaluation for heat and ashes showed the existence of an interaction between the factors, with total inhibition of germination in some treatments.