Levels of apoplastic inorganic phosphate (Pi) in leaves and Pi-transport activities of mesophyll cells were measured in situ in control and Pi-deficient plants. When detached leaves were fed a solution that contained 10 mM Pi, the apoplastic Pi levels, as measured by an infiltration method, remained almost constant. When the leaves were immersed in pure water, the apoplastic Pi level gradually decreased. With 50 mM Pi in the feeding solution, the level increased dramatically. The apoplastic Pi levels in Pi-deficient leaves were somewhat, but not very much lower than those in controls. When the immersion medium was changed to pure water 60 mm after feeding with 10 mM Pi, the apoplastic Pi levels started to decrease and then returned to the initial level. It is suggested that intracellular Pi may be transported back to the apoplast to maintain the apoplastic Pi levels at a constant value.Changes in cytoplasmic pH were measured during feeding of Pi to the leaves by use of the pH-sensitive fluorescent dye, pyranine after Yin et al. (l990a, b). On feeding of Pi the cytoplasmic pH decreased in Pi-deficient plants as a result of co-transport of Pi and protons in situ. After removal of Pi from the immersion medium, the cytoplasmic pH returned to the original value.
|頁（從 - 到）||563-568|
|期刊||Plant and Cell Physiology|
|出版狀態||Published - 1992 7月|
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