Short‐term pH regulation in plants

Abstract

Cellular pH regulation consists of two features: (i) Long‐term pH homeostasis, which ensures that all H+ or OH− produced in excess is ultimately removed from the cell and which requires metabolic energy; (ii) short‐term reactions of the cell(s) to sudden shifts in intracellular pH, in order to prevent acute disturbances of metabolism. Recent progress in measuring and understanding of mainly short‐term cellular regulation is summarized, including cellular responses to pH loads that arise from different sources such as external pH, weak acids/bases, protonophores, metabolic inhibitors, H+/cotransport, light and phytohormones. Whereas the plasma membrane H+ pump and metabolic adjustments may serve both long‐ and short‐term pH control, physico‐chemical buffering and the translocation of H+ from and to cellular compartments render only time‐limited capacity for the neutralization of pH loads and seem exhausted within minutes. In spite of the widespread opinion that, because of tight regulation, intracellular pH does not vary with time, there is good evidence for long‐lasting pH changes in plant cells, i.e. after hormonal stimulation, light/dark changes or carboxylation during crassulacean acid metabolism (CAM). This emphasizes that cytoplasmic pH, besides being well regulated, is essential not only for the regulation of membrane transport but also as a cellular messenger.

31P NMR Observations on the Effect of the External pH on the Intracellular pH Values in Plant Cell Suspension Cultures

“…These overshoot phenomena were apparently not caused by the inadequate supply has been reported in a limited number of other organisms, e.g. in the giant alga Chara corallina (25), the liverwort Riccia fluitans (5), and the root hairs of Sinapis alba (4). When pH.…”

“…One generalization that has emerged concerns the effect of pHO2 on the internal pH: it appears that pH,,, is relatively insensitive to changes in pH0 (11) and that the 'R. G (5).…”

Intracellular pH stability in the aquatic resurrection plant Chamaegigas intrepidus in the extreme environmental conditions that characterize its natural habitat

“…For example, although the cytoplasmic pH (pH cyt ) is often only weakly dependent on the external pH, this generalization tends to fail as the external pH reaches more extreme values that threaten the survival of the plant (Felle, 1988 ;Fox & Ratcliffe, 1990 ;Gout, Bligny & Douce, 1992). Hyperosmotic shock can also lead to pH changes, with maize root tips showing a small increase in both pH cyt and the vacuolar pH (pH vac ) (Spickett, Smirnoff & Ratcliffe, 1992) and Valerianella locusta leaf discs showing a decrease in pH cyt (Daeter & Hartung, 1990).…”

“…The steady-state intracellular pH values of plant and algal cells are often weakly dependent on the external pH, with pH cyt falling as the external medium becomes acidic and increasing as the external medium becomes alkaline (Felle, 1988 ;Fox & Ratcliffe, 1990 ;Gout et al, 1992). However increasing the external pH from 6 to 10 had no effect on the pH cyt and pH vac values of the submerged leaves of C. intrepidus, and caused only a small increase of c. 0n1 pH units in the pH cyt and pH vac values of the roots.…”

Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy

“…Reactions in the cytosol are exquisitely sensitive to changes in pH (Taiz 1992). pH regulation involves very complex processes in interaction with each other (Felle 1988;Rengel 2002;Sakano 1998;Smith and Raven 1979). Cytosolic pH can be regulated by pumping massive amounts of protons out of the cytosol into the lumen of the vacuole, in which pH varies according to plant species (Smith and Raven 1979;Taiz 1992).…”