Ecofisiologia de bancos de sementes de macaúba

Abstract

Structural and physiological aspects of macaúba diaspores allow seeds to persist in the soil and contribute to the conservation of natural populations over time. The objective of the first chapter of this thesis was to evaluate the influence of edaphic and climatic factors on the dynamics of the macaúba seed bank (SB). It was concluded that the macauba forms SB persistent in the soil. The P is the main edaphic factor linked to the entry of diaspores in the SB and high levels of Al and clay, organic matter, and sand contribute to the negative exit of the SB (insect predation, fungal and microbial contamination). However, the maintenance of intact embryos is independent of the studied edaphic factors. The positive output of SB is climatically controlled, dormancy is overcoming in winter/spring and germination occurs annually during the rainy season. On chapter two, the objective was to evaluate the effect of seasonality on longevity and the level of dormancy in macauba pyrenes maintained in simulated SB. The maintenance capacity of SB is related to the structural protection of the embryo, tolerance to water deficit and control of oxidative stress. The germination control in macauba seeds occurs by the gradual weakening of the resistance tissues (operculum and germ pore) associated with the increase in the embryo’s growth force. Both chapters show that the perception of environmental stimuli (especially, high temperatures) promotes the overcoming of dormancy, allocating the germination in the windows of climatic opportunities, contributing to the reproductive success, the wide distribution and the adaptation of the species to anthropized environments.