Changes in H+-ATP Synthase Activity, Proton Electrochemical Gradient, and pH in Pea Chloroplast Can Be Connected with Variation Potential

Abstract

Local stimulation induces generation and propagation of electrical signals, including the variation potential (VP) and action potential, in plants. Burning-induced VP changes the physiological state of plants; specifically, it inactivates photosynthesis. However, the mechanisms that decrease photosynthesis are poorly understood. We investigated these mechanisms by measuring VP-connected systemic changes in CO2 assimilation, parameters of light reactions of photosynthesis, electrochromic pigment absorbance shifts, and light scattering. We reveal that inactivation of photosynthesis in the pea, including inactivation of dark and light reactions, was connected with the VP. Inactivation of dark reactions decreased the rate constant of the fast relaxation of the electrochromic pigment absorbance shift, which reflected a decrease in the H+-ATP synthase activity. This decrease likely contributed to the acidification of the chloroplast lumen, which developed after VP induction. However, VP-connected decrease of the proton motive force across the thylakoid membrane, possibly, reflected a decreased pH in the stroma. This decrease may be another mechanism of chloroplast lumen acidification. Overall, stroma acidification can decrease electron flow through photosystem I, and lumen acidification induces growth of fluorescence non-photochemical quenching and decreases electron flow through photosystem II, i.e., pH decreases in the stroma and lumen, possibly, contribute to the VP-induced inactivation of light reactions of photosynthesis.

Relation of Photochemical Reflectance Indices Based on Different Wavelengths to the Parameters of Light Reactions in Photosystems I and II in Pea Plants

“…In particular, we previously showed that a reference wavelength equal to 570 nm is optimal for PRI calculation in this object [26], and that light-induced changes in PRIs (∆PRIs) were more effective for the estimation of NPQ in peas than the absolute values of these indices [62,64]. Additionally, it was known that durations of de-epoxidation and epoxidation in the xanthophyll cycle were about 10 min or more in peas [49]; in contrast, changes in the chloroplast light scattering were observed for about 1-2 min after the initiation or termination of illumination [38,65]. This means that we were able distinguish changes in PRIs related to activity of the xanthophyll cycle (slow-relaxing changes), and ones related to modifications of light scattering (fast-relaxing changes) on basis of a simple analysis of PRI relaxation without actinic light.…”

“…It is probable that different relations of different ∆PRIs to the photosynthetic parameters can be connected with different participation levels of the 526 and 545 nm components of change in reflectance [54] in the forming of light-induced changes in these ∆PRIs. We analyzed this hypothesis on the basis of the investigation of the slow-and fast-relaxing components in the investigated variants of PRIs, because the 526 nm component is traditionally related to changes in activity of the xanthophyll cycle (time of dark relaxation was about 10 min or more in peas [49]) and the 545 nm component is probably related to changes in chloroplast light scattering (time of dark relaxation was about 1-2 min in peas [65]). Figure 8 shows that the fast-and slow-relaxing components of the light-induced changes in the investigated ∆PRIs were weak under low and moderate intensities of actinic light (131 and 344 µmol m −2 s −1 ); however, these components greatly increased under the high intensities of actinic light (830 and 1599 µmol m −2 s −1 ).…”

Connection of the Photochemical Reflectance Index (PRI) with the Photosystem II Quantum Yield and Nonphotochemical Quenching Can Be Dependent on Variations of Photosynthetic Parameters among Investigated Plants: A Meta-Analysis

“…can reveal a new field for use of the photochemical reflectance index. In particular, PRI can potentially be used for fast and remote investigations of systemic photosynthetic responses induced by long-distance stress signals, including electrical [140][141][142][143][144][145][146][147], hydraulic [148], and Reactive Oxygen Species (ROS) [149] signals which strongly influence photosynthetic processes (e.g., the nonphotochemical quenching).…”

How to obtain cell volume from dynamic pH, temperature and pressure in plants

“…1.1 therein for a complementary Maxwell-type model). The possible mechanisms of the participation of pH changes on photosynthesis (Grams et al, 2009;Sukhov et al, 2014;Sherstneva et al, 2015;Sukhov et al, 2016) can also be included in the form of a phase-locked loop, thus closing the system of equations. The existence of oscillating behaviours in the investigated system, however, implies the existence of a control by feed forward or feedback loops, which are inserted into a self-regulating mechanism (Portes et al, 2015).…”