Desiccation Tolerance In Pleurostima Purpurea (velloziaceae): Gas Exchanges, Photosynthetic Pigment
(Aidar, Saulo de Tarso)
Desiccation tolerance in Pleurostima purpurea (Velloziaceae): gasexchanges, photosynthetic pigments and leaf relative water contentPleurostima purpurea (Velloziaceae), a rupicolous flowering speciesfound in rock outcrops in Rio de Janeiro state, southeastern Brazil,show notable capacity to endure vegetative desiccation. This study hadthe intent to show more details about the ecophysiological strategyused by these plants facing a drying ambient and the advantagesassociated with the process. For this, it was analised the gasexchanges, photosynthetic pigments content, and relative water contentof leaf tissues during desiccation and rehydration of cultivatedindividuals. They behaved typicaly as homeohydrics water savers undermoderated drought condition that, when aggravated, prosecute withpoikilohydric and poikilochlorophyllous behavior. After wateringsuspension, stomatic closing was observed under a relative leaf watercontent up to 90% that resulted in gas exchanges restrictions until theanabiosis. During this process, it was observed a delay in the leafrelative water content (RWCleaf) decrease comparing to the plant-soilrelative water content (RWCplant-soil). The chlorophylls degradationacompanished the RWCleaf decrease, which achived the minimum averagevalue of 17% without incur in leaves abscission, while its resynthesisjust begun after the full leaves rehydration. During all of thisprocess, the carotenoids content remained stable. Twelve hours of soilrehydration were sufficient for the respiration retake. A positivecarbon balance was observed since the 36th hour of rehydration, whenthe degree of stomatic opening became bigger than that observed for thecontrol group. Comparing with inicial conditions, 84 hours ofrehydration were sufficient to photosynthetic recovery, even just witha parcial recovery of chlorophyll content. As well as the leaf tissues,its roots might be desiccation tolerants.
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