Maturação de sementes de craibeira [Tabebuia aurea (silva manso) benth. & hook. f. ex s. moore]

Abstract

Tabebuia aurea (Silva Manso) Benth. & Hook. f. ex S. Moore, better known in the Northeast as craibeira, has fruit of the dehiscence type, occurring the natural dispersion of the seeds by the wind, making it difficult to harvest. Thus, studies involving the physiological maturity of the seeds are necessary to assist in the best harvesting season, thus obtaining seeds in maximum quantity and quality. The objective of this study was to evaluate the maturation of seeds of the craibeira, through physical, biochemical and physiological indexes to aid in the scheduling of these seeds. For this, 200 fruits were harvested on approximately twenty trees located in the municipality of Mossoró-RN, in September 2016, classified in three stages of maturation according to the epicarp color: dark green (stage I), light green (stage II) and beige (stage III). Part of the fruits and seeds harvested were initially evaluated for physical characteristics of length, width and weight of fruits, length, width and thickness of the seeds, weight of one thousand seeds, degree of humidity, as well as biochemical characteristics of electrical conductivity and chemical composition of the seeds. The remaining fruits remained in plastic trays covered with filo sacks, in post-harvest repose for 0, 5, 10 and 15 days in environmental conditions (30 °C, 45% RH), being evaluated in each period the degree of humidity and physiological characteristics of germination, germination speed index, mean germination time, root length, shoot length and dry mass of seedlings. Thus, the experimental design was completely randomized in a 3 x 4 factorial scheme (maturation stages x rest periods), with four replicates of 50 seeds. The physical and biochemical indexes can be used as indicators of the maturation of seeds, except fruit length, seed thickness, electrical conductivity and protein content. Seeds harvested at stage I require a post-harvest rest period of at least five days to complete the maturation process and reach maximum quality, however it still presents a high degree of humidity, post-harvest rest of 15 days aiming the storage of the seeds. Seeds harvested from stage II probably had already reached physiological maturity, since they already presented maximum germination and vigor in the newly harvested seeds, but also required post-harvest rest of 15 days in the environmental conditions of this study, for reduction degree of moisture, without compromising seed quality. Postharvest rest after five days impaired the physiological quality of the seed of the craibeira harvested at stage III