Crioconservação de sementes de ipê amarelo (Tabebuia chrysotrica (Mart. Ex. DC.) Standl.) e de ipê rosa (Tabebuia heptaphylla (Vellozo) Toledo.

Abstract

The uncontrolled utilization of the natural resources has provoked negative consequences, committing the genetic potential of many species. The Semi-Arid Tropic region of the Brazilian Northeast presents a big desert index and, consequently to the action of the autropia, many species are almost extinct, mainly those which have a great economic vaiue and that possess resistant wood that is used in constructions and in the popular medicine. Among them, the Ipe; which almost disappeared from this region, stands out. Their seeds present a little longevity, what has become a big obstacle in programs of reforestation and preservation of the species in germoplasm banks. The cryoconservation consists in submitting the seeds to cryogenics temperatures between - 140 and - 396 °C to preserve the physiological quality of the seeds for an uncertain time. However, all the species don't tolerate the cryoconservation. This evidences the need of constant researches on the development of protocols that make possible the techniques of cryoconservation of the species. In reason of that, this work had as objectives: 1) to determine the Limit Water Content for the Cryoconservation (LWCC) of the Ipe seeds and 2) to study the physiological quality of two species of Ipe (pink and yellow), that were submitted to 2 cryoconservation techniques (a) immersion in N3L at - 196°C; (b) conservation in N2L vapor - 170°C and 3 storages periods (0, 30, 60 and 90 days). The used statistic delineation was entirely casual. The factorial scheme 2 (varieties) x 5 (wet content), with 4 repetitions of 100 seeds and the cryoconservation with factorial scheme 2 (varieties) x 2 (cryoconservation temperatures) x 3 (storage periods) with 4 repetitions of 100 seeds were used to the LWCC determination. The obtained data were submitted to the variance analysis and the factors averages were compared to each other. Turkey's test, at 5% of probability and the operational program ASSIST AT 6.5 were utilized. According to the obtained data, it can be concluded that: (a) The Limit Water Content, for the cryoconservation (LWCC), was 4% w.b to the yellow Ipe and 6% w.b to the pink Ipe. (b) Both methods of cryoconservation, so much the immersion in liquid nitrogen as the seeds which were submitted to the nitrogen vapor at - 176°C were effective for the conservation of this biological material.