<b>Uma análise termobiológica da germinação</b>

Abstract

From the kinetics analysis of the process, one can assume the overall seed germination process as endergonic, and it does not occur unless certain energy threshold, represented by the enthalpy activation (H*) is reached. For germination, H* vary with temperature, and the analysis of its distribution over the entire temperature range suggests that at extreme temperatures H* is high and the process would cease due to an increasing requirement of energy eventually beyond the capacity of supply by the metabolic exergonic reactions. At temperatures below optimum the enthalpy change is positive, which implies that the germination rate is limited by the temperature dependence of processes synergistic to the embryo growth, whereas in the supra-optimum temperature range H* is negative, indicating the predominance of antagonistic partial steps. At optimum temperatures, the germination rate should be primarily limited by diffusion processes, such as imbibition. Thermal denaturation processes, denounced by their high H* values, should affect both the perception and transduction of the temperature signal within the seed. Considering the temperature dependence of the germination rate, the frequency distribution of isothermal germination may vary with temperature, and the analysis of those distributions suggests hypotheses about how the thermal signal is perceived by the seed.