Conservação de sementes de Catasetum (Orchidaceae): germinação e perfis lipídicos

Abstract

Orchidaceae is the largest plant family, widely diverse and evolving. They inhabit the most diverse environments, but unevenly, with more expressive populations in tropical regions. Orchids are among the most profitable species on the international plant market. Despite the use of asymbiotic culture techniques, the predatory collection continues to threaten natural populations. Species of the genus Catasetum Rich. ex Kunth, has been suffering intense extraction due to its high commercial value, however, most species do not have a threat assessment. In this way, ex-situ conservation aims to guarantee the preservation of the species as well as genetic variability, with emphasis on the storage of seeds in long-term germplasm banks. This study aimed to evaluate the use of pre-treatment for asymbiotic germination of seeds stored at low temperatures, relate the storage condition to preservation of long-term viability, as well as characterize the lipid profile of seeds of different species of orchids from the genus Catasetum. The data indicate that pre-treatment with 10% sucrose for a period of 24 hours at room temperature increases the germination rates of Catasetum barbatum, Catasetum complanatum and Catasetum galeritum, regardless of the culture medium used. And the best treatment found to maintain viability for 20 months for the seeds of Catasetum barbatum, Catasetum complanatum, Catasetum galeritum and Catasetum fimbriatum is the storage of seeds at a temperature of -18 ºC. The lipid profiles of the accessions analyzed here show variation among Catasetum species. The highest values of peroxidation index and double bond index in Catasetum gladiatorium suggest that this species is more susceptible to oxidative damage, implying deterioration during storage. The higher values of unsaturated fatty acids than saturated fatty acids suggest that low temperature is not the critical factor in Catasetum storage, which may contribute to seed longevity.