Analysis of the photosynthetic response induced by variation potential in geranium

Abstract

Electrical signals (action and variation potentials) caused by environmental stimuli induce a number of physiological responses in plants including changes in photosynthesis; however, mechanisms of these changes remain unclear. We investigated the influence of the variation potential on photosynthesis in geranium (Pelargonium zonale) under different conditions (control, low external CO₂ concentration, and actinic light absence). The variation potential caused by lamina burning induced a reduction in photosynthesis (decreases in effective quantum yields of photosystem I and II, CO₂ assimilation rate, and stomatal conductance) in unstimulated leaves under control conditions. Changes in the majority of light-stage parameters (photosystem I and II quantum yields, coefficients of photochemical and non-photochemical quenching, quantum yield of non-photochemical energy dissipation in photosystem I due to donor-side limitation) were correlated with a decrease in CO₂ assimilation rate. The changes were similar to those caused by lowering [CO₂]; their magnitudes decreased both under low external CO₂ concentration and without actinic light. These results support the hypothesis that Calvin cycle inactivation plays a key role in photosynthetic response induced by electrical signals. However, a decrease in electron transport through the PSI acceptor side also induced by variation potential was not correlated with a decrease in the CO₂ assimilation rate and did not depend on the external CO₂ concentration or actinic light intensity. Thus, we suggest that there are two different mechanisms of light-stage inactivation induced by the variation potential in geranium: one strongly dependent on dark-stage inactivation and one weakly dependent on dark-stage inactivation.

Variation potential propagation decreases heat-related damage of pea photosystem I by 2 different pathways

“…It is known 22 that strong inactivation of the Calvin cycle can be one of mechanisms causing PSII damage when plants are under stress. As a result, it was possible that VP-induced photosynthesis dark stage inactivation 8,[11][12][13] stimulated PSII damage under heating.…”

“…9 Our previous analysis showed that increased heat tolerance of PSI was caused by an electrical signal-induced photosynthetic response 8 that was mainly related to photosynthesis dark stage inactivation. 8,[10][11][12][13] VP-induced response is caused by changes in intra-and extracellular pH that is concomitant with VP generation. [14][15][16] pH-dependent decrease of HCO 3 :CO 2 ratio, 16 changes in aquaporin permeability, 12 and (or) changes in carbonic anhydrase activity 14 are potential mechanisms by which VP influences dark stage photosynthesis.…”

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.…”

“…These 'AP-like' spikes can take the lead over the long-term depolarization in mimosa, sunflower and bean, 42,51,52 join the depolarization and form the first fast depolarization in pumpkin, geranium and pea, 24,30,46 and be generated during the depolarization in mimosa, sunflower, tomato, pumpkin and cucumber. 11,43,47,51,53 However, VP can occur without 'AP-like' spikes, as well.…”

Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings

“…As discriminated from slowly developing photosyn thetic responses that can be associated not only with elec tric but also with hormonal signals [19,23], an associa tion between the rapid inactivation of photosynthesis with AP and VP was confirmed in some works [27,29,31,32]. Nevertheless, the mechanism of the influence of the elec tric reaction on photosynthesis is still under discussion.…”