Effects of water deficit on the physiology, biochemistry and morphology of the protocorms of the epiphytic orchid Laelia lobata Lindl.

• Ano de defesa: 2020
• Autor(a) principal: Bazalar, Valeria Paloma Ferrario
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Déficit hídrico; Epiphytic orchid; Laelia lobata; Laelia lobata Lindl.; Mecanismos de tolerância; Orquídea epífita; Tolerance mechanism; Water deficit
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/41/41132/tde-08052020-090529/

Epiphytic orchids are important components of the tropical and subtropical forests. In the epiphytic environment these are subjected to many stressful conditions, among which stand out intermittent rainfall or even drought. The strategies these orchids employ to survive and develop in such conditions are of great interest between researchers. In the present study we investigated some of the effects of water deficit on the physiology, biochemistry and morphology of protocorms of the epiphytic orchid Laelia lobate Lindl. The protocorm is a post-embryonic stage of the orchids, considered a simple and unique structure which is particularly unprotected but with a high ability to survive in a highly constrained environment. To mimic water shortage conditions, we used three different osmotic treatments adding polyethylene glycol (PEG) 6000 to a previously selected culture medium. It was observed that the decrease in water potential increased the survival of the protocorms, their photosynthetic activity, dry matter, and induced both a large accumulation of cuticle waxes as well as deep changes in the waxes composition. Moreover, it was also observed that L.lobata protocorms have stomata on the whole surface and present values of δ13 (-15 % ~ -14 %) which indicated that they putatively display crassulacean acid metabolism (CAM). On the other hand, the osmotic treatments provoked a marked reduction in the protocorms growth, in total soluble sugars content, cell wall monosaccharides, polyols and other carbohydrates, which are thought to be accumulated to act as osmoprotectans. The data contributes to a better understanding of the effects of water shortage on the protocorms of L.lobata and some of the tolerance mechanisms they display to cope with such stressful condition, highlighting that some responses differed from what was expected according to literature