Geomagnetic and strong static magnetic field effects on growth and chlorophyllafluorescence inLemna minor

Growth, physiological, biochemical and molecular changes in plants induced by magnetic fields: A review

The Earth's geomagnetic field (GMF) is an inescapable environmental factor for plants that affects all growth and yield parameters. Both strong and weak magnetic fields (MF), as compared to the GMF, have specific roles in plant growth and development. MF technology is an eco-friendly technique that does not emit waste or generate harmful radiation, nor require any external power supply, so it can be used in sustainable modern agriculture. Thus, exposure of plants to MF is a potential affordable, reusable and safe practice for enhancing crop productivity by changing physiological and biochemical processes. However, the effect of MF on plant physiological and biochemical processes is not yet well understood. This review describes the effects of altering MF conditions (higher or lower values than the GMF) on physiological and biochemical processes of plants. The current contradictory and inconsistent outcomes from studies on varying effects of MF on plants could be related to species and/or MF exposure time and intensity. The reviewed literature suggests MF have a role in changing physiological processes, such as respiration, photosynthesis, nutrient uptake, water relations and biochemical attributes, including genes involved in ROS, antioxidants, enzymes, proteins and secondary metabolites. MF application might efficiently increase growth and yield of many crops, and as such, should be the focus for future research.

Soybean Germination Response to Algae Extract and a Static Magnetic Field Treatment

The present study examines the separate and synergistic effects of macroalgal extract and static magnetic field (SMF) on the germination of soybean seeds (Glycine max (L.) Merrill), cv. Abelina, seedling growth, chlorophyll, and carotenoids content in leaves. Algal extract was produced from freshwater green macroalga (Cladophora glomerata) using ultrasound-assisted extraction. The germination tests were conducted in two stages. Firstly, different concentrations of extracts, 20%, 40%, 60%, 80%, and 100%, were applied to a paper substrate. The best results (taking into account germination percentage, seedlings length and weight, and pigments content in leaves) were observed for 20% and 80% extracts. At the same stage, germination of seeds exposed to SMF (exposure times for 3 and 12 min and magnetic inductions of 250 and 500 mT) was studied. The best developed seedlings were determined for the group treated at 3 min with a magnetic induction of 250 mT. In the final step, the simultaneous effects of 20% and 80% algal extracts and treatment with 3 min at 250 mT SMF were tested. Taking into account all the parameters, the simultaneous use of 20% extract and 3 min of 250 mT magnetic induction is recommended.

Static Magnetic Field (0.2-0.4 T) Stimulates the Self-Renewal Ability of Osteosarcoma Stem Cells Through Autophagic Degradation of Ferritin

Static magnetic field (SMF) can alter cell fate decisions in many ways. However, the effects of SMF on cancer stem cells (CSCs) are little-known. In this particular study, we evaluate the biological effect of moderate-intensity SMF on osteosarcoma stem cells (OSCs) and try to clarify the underlying mechanisms of action. First, we demonstrated that prolonged exposure to SMF induced the proliferation and tumorsphere formation in K7M2 and MG63 OSCs. Moreover, SMF promoted the release of ferrous iron (Fe²⁺ ) and provoked reactive oxygen species (ROS) in OSCs. Interestingly, SMF evidently triggered the autophagic degradation of ferritin, which is characterized by the activation of microtubule-associated protein 1 light chain 3 (LC3) and nuclear receptor co-activator 4 (NCOA4), and downregulation of ferritin heavy chain 1 (FTH1) in OSCs. Particularly, the colony-forming ability of K7M2 OSCs promoted by SMF was obviously abolished by using a small interfering RNA (siRNA) against NCOA4. Finally, treatment of the tumor-bearing mice with SMF did not affect the tumor volume or tumor mass, nor pulmonary metastasis of K7M2 OSCs, but the SMF-treated K7M2 OSCs caused a preference of pulmonary metastasis in a mouse model, which suggested that SMF might induce the metastatic characteristic of OSCs. Consequently, this paper demonstrates for the first time that the cumulative SMF exposure promoted the self-renewal ability of OSCs via autophagic degradation of ferritin, implying that ferritinophagy may be a potential molecular target for cancer. © 2021 Bioelectromagnetics Society.

Ameliorative Effects of a Static Magnetic Field on Hyssop (Hyssopus officinalis L.) Growth and Phytochemical Traits Under Water Stress

The present study was carried out in order to evaluate the promoting effect of a static magnetic field (SMF) on drought tolerance and medicinal properties in Hyssopus officinalis. In the current work, the effect of seed priming with SMF (45, 90, 200, and 250 mT for 5 min) was investigated in 60-day-old hyssop (H. officinalis) plants that were irrigated every 8 days. The assessments consisted of total dry mass, membrane integrity, photosynthetic pigment concentrations, polyphenol content, antioxidant enzyme activities, and antioxidant capacity. Compared with exclusively water stress, magnetopriming, particularly at 200 mT, significantly altered these parameters in the grown plants. At this intensity, the level of total dry mass, total chlorophyll, and polyphenol content increased by 94%, 2.5- and 7.7-fold, respectively. Also, the level of electrolyte leakage and malondialdehyde decreased by 35% and 33%. The reducing power, DPPH (1,1-diphenyl-2-picrylhydrozyl), and superoxide anion-scavenging activities were highly augmented as well. Magnetopriming at 200 mT increased catalase (+92%) and ascorbate peroxidase (+2.3-fold) activities. However, the highest activity of guaiacol peroxidase was recorded at 90 mT. Generally, the present study illustrated the positive effect of magnetopriming (200 mT) on improvement of drought tolerance in H. officinalis through protection of cellular membrane integrity, maintenance of photosynthetic pigment content, and alternation of antioxidant enzyme activities. Furthermore, the data showed this treatment (200 mT) not only had no negative effect on medicinal properties of H. officinalis, but also improved it via increasing total phenolic content and antioxidant capacity. Bioelectromagnetics. 2020;41:403-412. © 2020 Bioelectromagnetics Society.

Germination of soybean seeds exposed to the static/alternating magnetic field and algal extract

In the present study, the effect of the static and alternating magnetic field applied individually and in combination with an algal extract on the germination of soybean seeds (Glycine max (L.) Merrill) and chlorophyll content was examined. The exposure time of seeds to the static magnetic field was 3, 6, and 12 min, whereas to the alternating magnetic field was 1, 2.5, and 5 min. The static magnetic field was obtained by means of a permanent magnets system while the alternating magnetic field by means of magnetic coils. Algal extract was produced from a freshwater macroalga-Cladophora glomerata using ultrasound homogenizer. In the germination tests, 10% extract was applied to the paper substrate before sowing. This is the first study that compares the germination of soybean seeds exposed to the static and alternating magnetic field. The best effect on the germination and chlorophyll content in seedlings had synergistic action of the static magnetic field on seeds for 3 min applied together with the extract and alternating magnetic field used for 2.5 min. It is not possible to clearly state which magnetic field better stimulated the germination of seeds, but the chlorophyll content in seedlings was much higher for alternating magnetic field.

Retrospective analyses of archive phytotoxicity test data can help in assessing internal dynamics and stability of growth in laboratory duckweed cultures

High growth potential of duckweed species (Lemnaceae family) has been utilized in wide range of research and practical applications. Based on literature data, however, it can be assumed that duckweed populations maintain constant growth rates only when short periods are considered but can vary over longer time scales. This intrinsic instability in growth can affect the interpretation of growth data. Duckweed phytotoxicity tests are usually performed according to highly standardized protocols. Therefore the archive data provide an opportunity for retrospective comparisons. In the present study we collected growth (frond number- and frond area-based relative growth rates) and morphology (average frond and colony sizes) data from control treatments of phytotoxicity tests. All the analyzed tests were carried out with the same Spirodela polyrhiza (L.) Schleid. (giant duckweed) clone (RDSC ID No. 5501) under the same experimental conditions over more than four years. We aimed to assess the overall variability of the above parameters and to test if intrinsic growth patterns affect growth data in short-term. In general, the results reflected high stability of the measured parameters in long term but also indicated that some temporal variability is inevitable which can bias the comparability of growth tests. The frond area-based relative growth rate resulted in smaller coefficient of variation than the usually preferred frond number-based one. The results also revealed a negative correlation between mean growth rates and their coefficients of variation. Therefore, it would be advisable to introduce higher minimal growth rates and/or maximized tolerable coefficients of variation for control cultures into the standard duckweed growth inhibition tests. Analyses of growth data aggregated on seasonal basis indicated faster growth and larger mean frond size in laboratory duckweed cultures from mid-autumn till mid-spring than during summer and early autumn. But, in shorter term (∼50 days) we did not observe distinct trends in growth suggesting that the successive frond generations have no effect on growth traits within this time-scale. Our results point to the importance of assessing intrinsic growth dynamics in duckweed cultures and also to the re-usability of the already collected phytotoxicity data in addressing new research questions.

Low-Light Dependence of the Magnetic Field Effect on Cryptochromes: Possible Relevance to Plant Ecology

Various responses to static magnetic fields (MF) have been reported in plants, and it has been suggested that the geomagnetic field influences plant physiology. Accordingly, diverse mechanisms have been proposed to mediate MF effects in plants. The currently most probable sensor candidates are cryptochromes (Cry) which are sensitive to submillitesla MF. Here, we propose a quantitative approach of the MF effect on Cry depending on light intensity, and try to link it to a possible functional role for magnetic sensitivity in plants. Based on a theoretical evaluation and on a review of relevant data on Arabidopsis thaliana Cry 1, we point out that the MF effect on the signaling state of Cry, as well as the possible consequences of that effect on certain phenotypes (growth in particular) show parallel dependences on light intensity, being most prominent at low light levels. Based on these findings, we propose that Cry magnetosensitivity in plants could represent an ecological adaptation which regulates the amount of Cry signaling state under low light conditions. That hypothesis would preferentially be tested by studying sensitive and specific endpoints, such as the expression of clock proteins that are downregulated by Cry, but under light intensities lower than those used so far. Finally, we highlight that the low-light dependence of the MF effect described here could also apply to light-dependent functions of animal Cry, in particular magnetoreception which, from the present evaluation, would be based on the magnetic sensitivity of the photoreduction reaction, like in plants.