Criopreservação, germinação e morfoanatomia de sementes de Passiflora spp.

Abstract

Cryopreservation of seeds may be an alternative for the long term, taking into account the importance of conserving these species. The first chapter of this work details the evaluation of the germination of cryopreserved seeds of Passiflora spp., using traditional statistical tools and multivariate analysis. In the second chapter, results of biometry and anatomy of the seeds of these species are shown, in order to know their morphology and to identify possible cryoinjury after freezing. Results showed that, for most species, there is no difference between cryopreservation and conservation in the refrigerator, although for P. suberosa, germination percentage, mean time and synchrony displayed the best results under refrigerator conditions, and for P. tenuifila, the germination time, mean velocity and uncertainty presented higher results on cryopreserved seeds. The desiccation of the seeds did not generate negative effects on the physiological quality, since high germinability was observed even after cryopreservation. For the evaluated species, tolerance to desiccation was observed, with high germinability even under the reduced humidity of 3.4%. The results presented here make it clear that there is no need for desiccation of the seeds of the species for cryopreservation purposes. The variables germination, speed and synchrony showed positive correlations and are directly related to the physiological quality, contributing to a better evaluation of seed vigor. Six types of seed ornamentation were observed: cross-linked to the species P. coccinea, finely crosslinked to P. edulis, crosslinked foveolate to P. gibertii and P. setacea, alveolate reticulated to P. maliformis and P. tenuifila, coarsely reticulated to P. morifolia and falsifoveolate reticulated for P. suberosa. Seeds presented large variations in length (3.29 to 6.25 mm), width (2.25 to 4.53 mm) and thickness (0.18 to 2.09 mm), with mean values of 4.63 mm for length, 3.28 mm for width and 1.51 for thickness. The longitudinal length of the tegument varied from 3520 μm in P. maliformis to 5250 μm in P. gibertii, with a mean of 4770 μm. It was verified that some seeds suffered ruptures in the integument, due to the conditioning in liquid nitrogen. The results presented in this work bring evidence that seeds from the studied passion fruit species can be cryopreserved without the necessity of desiccation, maintaining its physiological quality after freezing. It was also observed that the fissures presented limited depth which did not induce physiological damage to the embryo and endosperm.