Aspectos fisiológicos relacionados ao armazenamento de frutos e envelhecimento de sementes de macaúba [Acrocomia aculeata (Jacq.) Lodd. ex Mart.]

Abstract

Acrocomia aculeata (Jacq.) Lood. ex Mart., popularly known as macaúba, is widely spread in the Americas and considered the palm tree most widely distributed in Brazil, existing largely in Cerrado’s areas. Due to the large oleaginous potential of its fruits, the economic importance of the species is recognized and it may be used in the pharmaceutical, cosmetics, food and biodiesel industries. This study aimed to analyze the physiological and biochemical changes occurring in macaw palm seeds during ageing under natural and artificial conditions. The effects of fruit storage under different conditions (laboratory, nursery, cold chamber and freezer) were tested on the embryo growth cultured in vitro, and it was evaluated the possible role of vitamin E and defense related phytohormones as markers of embryo growth. Fatty acids profile and changes in the main seed reserve compounds were determined. We also evaluated the effects of accelerated ageing on macaw palm embryos viability, on lipid peroxidation, on electrolyte leakage, on hydrogen peroxide (H2O2) production and on antioxidant enzymes activity in the embryo after imbibition of artificially aged seeds. Results showed that storing fruits in laboratory was the most efficient method for maintaining embryo viability. The antioxidants mechanisms in the seeds (vitamin E), along with abscisic acid were effective in protecting the endosperm and the embryo against oxidative stress during storage, and were considered good indicators of embryo growth to obtain plantlets in vitro. Fatty acids profile of the different fruit structures did not change during storage, regardless the condition evaluated. The fatty acids composition of the embryo was very similar to that of the mesocarp, predominating monounsaturated fatty acids, while in the endosperm, saturated fatty acids are predominant. Accelerated ageing showed that loss of seed viability, lipid peroxidation and membrane damage during ageing are related. The production of H2O2 in imbibed embryos after ageing revealed that the enzymatic antioxidant system was not completely efficient in removing reactive oxygen species during imbibition. Such information contributes to storage macaw palm fruits in conditions that minimize the damages caused by ageing, maintaining embryo viability longer.