Judged from several parameters, growth of barley seedlings is diminished by a combination of a static and an alternating magnetic field, which corresponds the ICR of Ca2+. No ferrimagnetic particles were found up to now in barley plants, which could be directly influenced by MF. Also a radical pair effect e.g. on charge separation during photosynthesis as primary magnetoreceptor is improbable in the dark. There are also hardly other environmental stress factors, which could force radical generation. Furthermore, radical pair reactions should not show a resonant response like the one seen here, in the gradient experiments, which showed maximum effects for BDC = 65 μT and f(BAC) = 50 Hz, directly relating the ICR equation for Ca2+ (1). Finally the radical pair mechanism should not be influenced by as low field strengths as were applied here. Seemingly the visible appearance as well as regulative processes of the plants are similarly pertained by the applied EMF, whereby there are possibly morphological manifestations lasting for extended times beyond the phase of exposition to Ca2+ ICR.
Several theoretical models try to explain the ICR effect and its possible biological implications. The model of Binhi [28
] is based on an interference mechanism of quantum states of ions within protein cavities. Different types of orbits are considered, and a formula has been developed for the magnetic field-dependent part of the dissociation probability of an ion-protein, in order to explain the resonance behavior of the system. More recent experiments could show similar effects in the absence of proteins or interface building structures like lipid membranes: A resonant EMF effect could already be shown by the change of the conductivity of amino acid solutions, if they were exposed to the respective ICR condition [29
]. Such results challenged additional theoretical models. The major difficulty in rationalizing the effects as a result of ICR is the requirement of undisturbed Larmor
precession of charged particles in a condensed phase, viz. aqueous environment, at ambient temperatures. It has been based on the quantum electrodynamical properties of water, which however are still only poorly studied. Del Giudice et al. [31
] propose a two phase state of water with regions providing quantum coherence, and thereby a decoupling factor against the surrounding thermodynamical equilibrium. Already earlier Novikov et al. [32
] suggested a self-organizing mechanism for larger ion assemblies and substantiated this theory by applying motion equations for basic forces of only ~10-21
N for the Lorentz
ean force on an ion from an external magnetic field. Further, the coupling of electron spin states for comparably long distances and time windows could provide a resonant EMF effect for radical pairs [33
], representing a special case of the common radical pair effect and enhancing its sensitivity for EMF by orders of magnitude. As mentioned above, it is very difficult to explain the EMF effects found in the present study by the established mechanisms for biological magnetoreception: ferrimagnetic particles or the radical pair mechanism. Two questions remain: The existence of a predictable resonance phenomenon, and the high sensitivity to EMF of only some 10–100 nT., which must be overlaid to a static magnetic field at most in the order of the geomagnetism (≤100 μT).
is an important factor for the bioregulation in plants. So it is surely a useful approach to postulate a modulation of the Ca2+
supply of the plants by the electromagnetic impact, also proposed by Huang et al. [34
], and subsequently to consider specific aspects of Ca2+
regulation in plants, compiled by Medvedev [20
]. It is obvious, that effects should preferentially occur at locations with increased Ca2+
-concentrations and on Ca2+
-mediated transport systems. The Ca2+
-concentration in cell walls and vacuoles is up to 100 times higher than in the cytosol, the cell membranes provide sharp gradients of Ca2+
concentration, along with a electrochemical potential, which is widely modified by the activity of membrane channels. Phytochrome A activity and circadian regulation are driven by Ca2+
oscillations, which are discussed as part of the "biological clock" of plants [35
]. The influence on cellular structure, a subsequent smaller growth, damages on the photosynthetic apparatus, and decreased Chl and carotenoid concentrations caused by calcium and magnesium deficiency are described for barley plants by Klyachenko [36
]. These effects were qualitative similar, even though less pronounced, in the current experiments, which would be consistent with an influence of the used MF and EMF on the Ca2+
Lower PChlide content in etiolated ICR leaves could be connected with reduced amount of plastids per cell as well reduced plastid size, or intraplastid membrane quantity – parameters genetically programmed for each plant cell species. The ratio between the absorption intensity of PChlide650 and PChlide630 in Ca2+ ICR exposed leaves belongs rather to the unexpected result. It is known that many treatments, like exogenous phytohormones, high temperature, irradiation with far-red light and some mutations induce the enhancement of photononactive PChlide. Reduced rate of the PChlide resynthesis as well as its end level under ICR conditions could be results on limited biosynthesis of PChlide, NADPH or POR.
As rate of Shibata shift and Chlide esterification is practically equal [22
], it is obviously, that applied treatment has not significant influence on the Chl formation in short illuminated etiolated leaves. Lower Chl content and retarded plant development during prolonged growing of ICR barley point to pleiotropic effects of used EMF, connected probably with realization of genetic program and energy metabolism. More detail experiments are needed to observe what of this is disrupted under ICR conditions.
Grossly speaking, all processes depend from the intracellular water supply, and just here the data indicate an increased drought stress for the ICR exposed plants. Considering the data shown in fig. , already a decreased water uptake could be the matter more than an increased evaporation. In [37
], wheat plants were investigated after applied drought stress, they indicated an enhanced oxidative damage to photosynthetic pigments, proteins and lipids. Essential enzymes like superoxide dismutase, catalase and glutathione reductase showed a decreased activity. Lastly Le Lay et al. [38
] report desiccation-induced delays and reductions of the chlorophyllide transformation in etiolated barley leaves, similar to our observations on the ICR exposed plants. Because also a temporary water deficit may cause irreversible damages, the observed adverse manifestations on the plants long time after finishing ICR exposure can well be rationalized.