Maturação fisiológica de sementes de tucumã (astrocaryum aculeatum g. mey. arecaceae) em uma área da Amazônia central

Abstract

In the family Arecaceae, countless species produce edible fruits of significant nutritional value and high economic potential. Astrocaryum aculeatum G. Mey. is such a species, which its fruit is known as tucuma. This plant is a single-stipe palm with an erect trunk approximately 25 m high and 30 cm in diameter. It is propagated by seed and there is commonly a delay in germination start. Palms often show slow and irregular germination, and maturation is one of the factors involved. The process of seed maturation influences the physiological quality and its study in seed technology tries to determine the ideal harvest conditions for obtaining top quality seeds. Specifically, this work aims to identify the point of physiological maturity which produces Astrocaryum aculeatum seeds which have maximum viability and vigor. The investigation was carried out in three studies. To identify morphological indicators the morphological characteristics of the fruits and pyrenes were evaluated. For seeds, anatomical characteristics were used along with the qualitative and quantitative content of reserves. In the study concerning the influence of the period of time of ripening on the seedling emergence the following parameters were considered: the water content, the fresh and dry mass of the pyrene, accumulated reserves, percentage of germinability, seedling emergence, dead seeds, dormant seeds, the index of velocity, and the mean time of emergence. The study of post-harvest ripening was carried out on seeds obtained from fruits 0, 5, 10, 15 and 20 days after harvesting, and the parameters analyzed were: water content of the fruits, pyrenes and seeds, the percentage germinability, seedling emergence, dead seeds, protein content, the index of velocity, the mean time and final time of emergence. The point of seed physiological maturity of tucumã occurred between 153 and 169 days after the opening of the spathe. The color of the exocarp was not a good indicator of the seeds physiological maturity. Better morphological indicators were: yellow or deep viii orange color of the mesocarp, bright black color of the endocarp, light brown or dark-ferruginous brown color of the tegument, hard consistency of the endocarp, strong consistency of the endosperm, as well as the point maximum length, thickness and fresh mass of the pyrene. tucumã seeds have reserve materials of proteins, lipids and carbohydrates in the form of pectic polysaccharides. At 90 days after the opening of the spathe, the embryo displayed differentiation of the primordial leaves. The period of time influences the physiological and the germination of seeds of A. aculeatum. At 135 days after the opening of the spathe, the seeds showed a high percentage of seeds mortality and at 153 days there was a higher germinability and seedlings emergence. Tucumã seeds extracted from fruits harvested at the beginning of spontaneous detachment of the bunch, showed higher physiological performance than those subject to periods of post-harvest ripening.