Light-induced changes of cytosolic pH in Eremosphaera viridis: recordings and kinetic analysis

Effects of heat and drought stress on post‐illumination bursts of volatile organic compounds in isoprene‐emitting and non‐emitting poplar

“…This effect could trigger the activation of LOX, which has its activity optimum at pH values of 6.3 and 4.5 (Hatanaka ). Conversely, fast dark‐to‐light transitions lead to an alkalization (Bethmann et al ), which might explain why fast, repeated light‐to‐dark transitions do not cause PIBs, as has been shown previously using grey poplar leaves (Graus et al ).…”

“…It has been argued that these so‐called ‘post‐illumination bursts’ (PIBs) might be caused by fast changes in intracellular pH values and consequently membrane stability after fast light‐to‐dark transitions (Brilli et al ). In the algae Eremosphaera viridis , a quick light‐to‐dark transition leads to a short‐term (1–3 min) acidification of the cytosol (Bethmann et al ). This effect could trigger the activation of LOX, which has its activity optimum at pH values of 6.3 and 4.5 (Hatanaka ).…”

pH regulation in an acidophilic green alga – a quantitative analysis

“…Membrane resistance was measured with two impaled microelectrodes; one electrode was used to inject a current of 0.1 nA for 400 ms every 10 s while the other electrode registered the resulting membrane potential change (membrane resistance = membrane potential change/injected current). Intracellular ion activities were measured using ion‐selective liquid membrane microelectrodes (Ammann, 1986), as described in detail earlier (Bethmann et al ., 1995, 1998). Sensors for ion‐selective microelectrodes were from Fluka (H + ionophore no.…”

“…Nonturgor‐resistant ion‐selective microelectrodes were used. Impalement was made possible by turgor reduction, which was achieved by adding 400 mM sorbitol to artificial pond water (Bethmann et al ., 1995, 1998). As shown earlier (Thaler et al ., 1992), neither the steady‐state value nor the light‐dependent changes of the membrane potential are altered by sorbitol at this concentration.…”

“…Proton‐coupled transport processes and H + ‐consuming or H + ‐generating metabolic reactions continuously threaten to change the cytosolic pH, which has to be kept constant within narrow limits. In plant cells, sudden illumination or darkening causes significant cytosolic pH changes that are compensated within a few minutes (Guern et al ., 1991; Bethmann et al ., 1998). There is increasing evidence that changes in cytosolic pH are a functional part of intracellular signal transduction (Felle, 2001).…”