Action potential in Chara cells intensifies spatial patterns of photosynthetic electron flow and non-photochemical quenching in parallel with inhibition of pH banding

Abstract

Characean cells exposed to illumination arrange plasma-membrane H(+) fluxes and photosynthesis in coordinated spatial patterns. The limited availability of CO(2) in alkaline bands accounts for the lower effective quantum yield of photosystem II (DeltaF/F(m)') in chloroplasts of these bands compared to acidic zones. The effect of electrically triggered action potential on the spatial distribution of photosynthetic parameters (DeltaF/F(m)' and non-photochemical quenching, NPQ) and extracellular pH was studied with fluorescence imaging and pH microelectrodes. In the resting cell at a range of light intensities, the periodic profile of extracellular pH is parallel to the profile of NPQ and antiparallel to that of DeltaF/F(m)'. After triggering the action potential, the pH banding temporarily disappeared, but in contrast, the differences in effective quantum yield and NPQ patterns became more apparent. The transient changes in pH-banding, effective quantum yield and non-photochemical quenching are discussed in relation to alterations in intracellular Ca(2+) and H(+) concentrations during and after the action potential.

Analysis of the photosynthetic response induced by variation potential in geranium

“…A number of publications have demonstrated the influence of electrical signals on photosynthesis (Fromm and Eschrich 1993;Fromm and Fei 1998;Koziolek et al 2003;Bulychev et al 2004;Lautner et al 2005;Kaiser and Grams 2006;Hlaváčková et al 2006;Fromm and Lautner 2007;Grams et al 2007Grams et al , 2009Krupenina and Bulychev 2007;Krupenina et al 2008;Sukhov et al 2008a, b;Pavlovič et al 2011); however, these results are contradictory. In particular, electrical signals can induce rapid (*minutes) reduction in the CO 2 assimilation rate (Koziolek et al 2003;Lautner et al 2005;Grams et al 2009), a decrease in quantum yields of photosystem I (PSI) (Grams et al 2009) and photosystem II (PSII) (Koziolek et al 2003;Lautner et al 2005;Grams et al 2009), an increase in photochemical fluorescence quenching and a lowering in non-photochemical quenching (Pavlovič et al 2011).…”

“…Bulychev and co-workers (Krupenina and Bulychev 2007;Krupenina et al 2008) suggested a possible mechanism of AP-induced photosynthesis reduction in Chara algae. According to this hypothesis, calcium influx during AP causes an increase in Ca 2?…”

Variation potential in higher plants: Mechanisms of generation and propagation

“…For example, ESs induce gene expression, [16][17][18] phytohormone synthesis, 17,19,20 phloem transport decrease, 21 changes in root absorption, 11 activation of respiration, [22][23][24][25][26] and inactivation of photosynthesis. 23,24,[26][27][28][29][30][31] Retivin et al 32 hypothesized that the ultimate role of these physiological changes is the increase of plant resistance to stressors. Indeed, it has been shown that ESs can have a positive influence on resistance to stressors at the whole plant level, 32 including increasing photosynthetic machinery resistance, 30,33 which is strongly connected with inactivation of photosynthesis.…”

Transient removal of alkaline zones after excitation ofCharacells is associated with inactivation of high conductance in the plasmalemma

“…6,7 The alternated pattern of broad acidic and narrow alkaline zones, known as the pH banding phenomenon, is mirrored by the spatial pattern of photosynthetic activity in a single layer of immobile chloroplasts. 8 The pH banding pattern vanishes in darkness and is smoothed transiently after the propagation of action potential along the cell, 9 while the photosynthetic pattern becomes temporarily enhanced. 8 The long-lasting impact of AP on H + transport (pH banding) and photosynthesis (chlorophyll fluorescence) in characean algae is consistent with its possible regulatory role in these processes.…”

“…8 The pH banding pattern vanishes in darkness and is smoothed transiently after the propagation of action potential along the cell, 9 while the photosynthetic pattern becomes temporarily enhanced. 8 The long-lasting impact of AP on H + transport (pH banding) and photosynthesis (chlorophyll fluorescence) in characean algae is consistent with its possible regulatory role in these processes. The AP propagation inhibits pH banding and selectively suppresses photosynthesis in alkaline cell areas for the period of 15-30 min, while the signal itself (AP) lasts typically few seconds.…”