New Phytologist Symposium Systems biology and ecology of CAM plants edition:34 location:Tahoe City, CA, USA date:15-18 July 2014
The diel, intracellular fluxes of malate across the tonoplast are a crucial feature of crassulacean acid metabolism. Nocturnally accumulated malate exits the vacuole during daytime and decarboxylation liberates CO2 for subsequent processing into organic carbohydrates via Rubisco. It is of vital importance that the decarboxylation reactions keep up with malate efflux from the vacuole to prevent over-acidification of the cytoplasm, which has recently been showed to induce chlorenchyma cell death and leaf necrosis. Although the photosynthetic photon flux density (PPFD) has been found an important determinant of organic acid remobilization out of the vacuole, the precise mechanisms and their interaction with environmental parameters, responsible for this export process are still matter of conjecture. Therefore the influences of light on malate processing were investigated in more detail in the obligate crassulacean acid metabolism (CAM) bromeliad Aechmea ‘Maya’. Besides continuous light and dark treatments plants were provided with different low fluence monochromatic light treatments (10 μmol m-2 s-1) such as blue (470 nm), green (530 nm), red (630 and 660 nm) and far red (735 nm). Determinations of malic and citric acid, titratable acidities, cell sap pH and cell sap osmolalities were performed to shed more light on the intracellular movements of malate.