Light-dependent pH changes in leaves of C3 plants

Abstract

Chloroplasts, mesophyll protoplasts, cytoplasts, vacuoplasts, vacuoles and leaves were stained with pH-indicating fluorescent dyes of differing pK values. Fluorescence microscopy was used to obtain information on the intracellular and intercellular distribution of the probes. The kinetics of blue or green fluorescence emitted from chloroplasts, protoplasts, cytoplasts and leaves was measured during illumination with red light. The intensity of light used for fluorescence excitation was so low that it had little effect on photosynthesis. In leaves, fluorescence signals emitted from chloroplasts were small and usually insignificant compared to signals originating from the cytosol. Both indicated light-dependent alkalization and reversal of alkalization on darkening. Vacuolar signals were opposite in sign to cytosolic signals. They indicated acidification of the vacuole in the light-dark transient and reversal of this effect on darkening.

A Reliable and Non-destructive Method for Monitoring the Stromal pH in Isolated Chloroplasts Using a Fluorescent pH Probe

“…There was almost no detectable proton gradient across the inner envelope membrane of plastids under these conditions, probably due to the fact that the plastids in the suspension-cultured cells were not fully functional because sugars were provided in the culture medium ( Shen et al, 2013 ). These results highlight the difficulty in measuring the stromal pH of green chloroplasts due to the interference from the chlorophyll fluorescence ( Yin et al, 1990 ; Shen et al, 2013 ).…”

Photosynthetic activity triggers pH and NAD redox signatures across different plant cell compartments

“…In higher plants, indirect indications for light-induced changes in cytosolic pH were reported, such as light-induced depolarisation of the plasma membrane (Hansen et al, 1993;Vanselow et al, 1989). Further, indirect evidence was reported from the use of fluorescent dyes, such as pyranine or 5-carboxyfluorescein diacetate, in illuminated leaves or protoplasts (Siebke et al, 1992;Yin et al, 1990), which were further fractionated into cytosolic and vacuolar fractions. By employing the genetically encoded pH sensor cpYFP, we were able to directly monitor light-induced alkalisation and to resolve its temporal signature in mesophyll tissue of true Arabidopsis leaves.…”

“…While stromal pH dynamics have been investigated at depth, aided by the use of isolated chloroplasts and thylakoid membranes (Demmig and Gimmler, 1983;Heldt et al, 1973;Waloszek and Więckowski, 2004), their in vivo impact on cellular compartments beyond the chloroplast has remained largely unexplored, due to the technical challenge of cell compartment-specific pH measurements. Historically pH-sensitive microelectrodes and chemical fluorescent dyes were used for measurements in large algal and plant cells (Felle and Bertl, 1986;Raven and Smith, 1980;Siebke et al, 1992;Steigner et al, 1988;Thaler et al, 1992;Yin et al, 1990), but the difficulty to discriminate unambiguously between subcellular compartments hampered more systematic exploration.…”

Intracellular pH in Cnidarian-Dinoflagellate Symbiosis

“…The pH i values quantified in this study fall within those expected for eukaryotic cells, which typically maintain their cytosolic pH between 7 and 7.4 , and are similar to light-adapted pH i values measured in other marine algae . Furthermore, the more alkaline pH i of Symbiodinium seen in the light than in the dark was consistent with the effect of light observed in higher plants (Yin et al 1990). Light-induced alkalinisation is likely a by-product of physiological changes in the Symbiodinium cell's cytoplasm during photosynthesis.…”