Change in H+ Transport across Thylakoid Membrane as Potential Mechanism of 14.3 Hz Magnetic Field Impact on Photosynthetic Light Reactions in Seedlings of Wheat (Triticum aestivum L.)

Abstract

Natural and artificial extremely low-frequency magnetic fields (ELFMFs) are important factors influencing physiological processes in living organisms including terrestrial plants. Earlier, it was experimentally shown that short-term and long-term treatments by ELFMFs with Schumann resonance frequencies (7.8, 14.3, and 20.8 Hz) influenced parameters of photosynthetic light reactions in wheat leaves. The current work is devoted to an analysis of potential ways of this ELFMF influence on the light reactions. Only a short-term wheat treatment by 14.3 Hz ELFMF was used in the analysis. First, it was experimentally shown that ELFMF-induced changes (an increase in the effective quantum yield of photosystem II, a decrease in the non-photochemical quenching of chlorophyll fluorescence, a decrease in time of changes in these parameters, etc.) were observed under the action of ELFMF with widely ranging magnitudes (from 3 to 180 µT). In contrast, the potential quantum yield of photosystem II and time of relaxation of the energy-dependent component of the non-photochemical quenching were not significantly influenced by ELFMF. Second, it was shown that the ELFMF treatment decreased the proton gradient across the thylakoid membrane. In contrast, the H+ conductivity increased under this treatment. Third, an analysis of the simplest mathematical model of an H+ transport across the thylakoid membrane, which was developed in this work, showed that changes in H+ fluxes related to activities of the photosynthetic electron transport chain and the H+-ATP synthase were not likely a mechanism of the ELFMF influence. In contrast, changes induced by an increase in an additional H+ flux (probably, through the proton leakage and/or through the H+/Ca2+ antiporter activity in the thylakoid membrane) were in good accordance with experimental results. Thus, we hypothesized that this increase is the mechanism of the 14.3 Hz ELFMF influence (and, maybe, influences of other low frequencies) on photosynthetic light reactions in wheat.

The Effect of an Extremely Low-Frequency Electromagnetic Field on the Drought Sensitivity of Wheat Plants

“…In our experiments, the MF did not affect the main indicators of the light-dependent stage of photosynthesis (Fv/Fm, Φ PSII , NPQ) when plants were grown in the absence of the stressor (groups “Control” and “MF”) ( Figure 4 ). This agrees with the data from the literature, according to which the activity of photosynthesis, as well as the morphometric parameters, does not change under the action of MFs with characteristics similar to ours [ 13 , 14 , 18 ]. At the same time, some studies have demonstrated the stimulating effect of the MF [ 2 , 8 , 9 , 10 ].…”

“…At the same time, some studies have demonstrated the stimulating effect of the MF [ 2 , 8 , 9 , 10 ]. It has been shown that the MF influence is realized due to both changes in the number of structural components (photosynthetic pigments and individual photosynthetic enzymes, for example, Rubisco) and changes in the activity of the light-dependent reactions associated with the electron transport chain and changes in the rate of absorption of CO 2 [ 2 , 8 , 10 , 13 , 14 , 19 , 33 , 34 ].…”

“…In the case of alternating MFs of relatively low intensity, the effects are often weakly expressed or absent under stationary conditions [ 11 , 12 ], but they manifest themselves during transient processes when the environmental conditions change. In particular, in our previous works, such a pattern was established in relation to the activity of photosynthesis and the electric potential in wheat plants under the action of an alternating MF with a frequency of 14.3 Hz and an intensity of 3–180 μT, and the greatest effect was revealed under the influence of an ELF MF of 18 µT [ 13 , 14 , 15 ].…”

Effect of extremely low-frequency magnetic fields on light-induced electric reactions in wheat

“…Some works showed that low strength low-frequency MF is capable of affecting photosynthetic processes in plants. 5 , 7 , 9 , 10 In our recent works, the effect of the field with analogous parameters was shown to be capable of increasing efficiency 12 and progression rate 11 of light reactions of photosynthesis in wheat seedlings. The field-induced enhancement of proton leakage across the thylakoid membrane, as well as the stimulation of an additional H + flux caused by an increase in Ca 2+ concentration due to the activation of the H + /Ca 2+ antiporter, were suggested as key mechanisms.…”

“…The parameters of MF acting on the plants were chosen based on the most pronounced effects found during the analysis of frequency-amplitude dependency of the effect ELFMFs on photosynthesis, performed earlier. 11 , 12

Figure 1. Effect of extremely low-frequency MF on the parameters of light-induced electric reaction of the wheat seedlings.

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