Levels of ABA, its precursors and dehydrin-like proteins during mangrove leaf development and senescence

Abstract—Abscisic acid (ABA) and dehydrin proteins are thought to confer tolerance to plant tissue under physiological stress and drought. Rhizophora mucronata, a true mangrove species, is subjected to physiological drought from fluctuating high saline conditions where leaf loss or senescence is considered a possible regulation mechanism to combat stress. Levels of ABA and proteins that cross reacted with an anti – dehydrin antibody were assessed through development with the aim of correlating these factors to physiological water stress or salinity stress in R. mucronata leaves. Younger leaves showed lower levels of ABA than mature and senescing leaves. In situ production and translocation from mature to younger leaves may contribute to these observations. The presence of ABA in senescing leaves is thought to be due to the presence of low levels of physiological activity. Proteins detected by anti–dehydrin antibody require cDNA confirmation, but the visibly increasing intensity of a band at ~64kDa through development suggests potential correlation to drought or salinity stress which is expected to be maximal in maturing leaves. The absence of the dehydrin–like proteins in senescing leaves is postulated to be due to the lack of energy investment to synthesise these proteins in dying leaves.