Armazenamento de sementes de orquídeas em diferentes condições de temperatura e umidade

Abstract

Orchidacae is cited as the largest plant family (about 20-25 thousand species). Some species have great economic importance, so with the intense degradation of their habitats, has resulted in extinction in native populations. One capsule of this family can contain hundreds to thousands of seeds, seed conservation can be a very important strategy. For the analysis of physiological quality and monitoring of conservation of seed in storage, the most used method is the germination test associated with the tetrazolium test. The reduction of temperature and air humidity tends to increase the shelf-life of seeds. The liquid nitrogen temperature (-196° C) can provide greater preservation, though this response is not always observed. The objective was to evaluate the germination and viability of four species of the Orchid genus Cattleya (Cattleya purpurata, C. tigrina, C. amethystoglossa, C. brevicaulis) conditioned in three levels of water content in the seed (1.5, 12%), 6.4 and in three different conditions of storage environment temperature (5° C, -18° C and -196° C), for nine months of storage. Stored seed were evaluated for germination tests, index of seed velocity, tetrazolium test and evaluation of oxidative damage caused by storage period, such as malondialdehyde (MDA), peroxidase (PRX), superoxide dismutase (SOD) and soluble proteins. The experimental design was completely random and factorial arrangement of treatments (combined storage temperature and seed moisture) x storage periods. The variance analyses were applied and the treatments were compared by Tukey test. Among all the proposed storage conditions and water content of the seeds the best results highlighted that the seeds remain viable for more time with water levels of 6.4% and kept in liquid nitrogen. With the exception of C. purpurata, the other species also presented results for 5° C and -18°C storage with water levels at 6.4%. The biochemical results have shown that over time of storage, there is loss of viability and alterations of compounds, even with seeds conserved in liquid nitrogen.