High magnetic field induced changes of gene expression in arabidopsis

Interaction effects of magnetized water irrigation and wounding stress on Cd phytoremediation effect of Arabidopsis halleri

In this study, the phytoremediation efficiency of Arabidopsis halleri L. in response to mechanical injury were compared between those irrigated with magnetized water and those irrigated with normal water. Under normal irrigation treatment, wounding stress increased malondialdehyde (MDA) concentrations and hydrogen peroxide (H2O2) levels in A. halleri leaves significantly, by 46.7-86.1% and 39.4-77.4%, respectively, relative to those in the intact tissues. In addition, wounding stresses decreased the content of Cd in leaves by 26.8-52.2%, relative to the control, indicating that oxidative damage in plant tissues was induced by mechanical injury, rather than Cd accumulation. There were no significant differences in MDA and H2O2 between A. halleri irrigated with magnetized water and with normal water under wounding conditions; however, the activities of catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) in the leaves of plants treated with magnetized water were significantly increased by 25.1-56.7%, 47.3-183.6%, and 44.2-109.4%, respectively. Notably, under the magnetic field, the phytoremediation effect of 30% wounded A. halleri nearly returned to normal levels. We find that irrigation with magnetized water is an economical pathway to improve the tolerance of A. halleri to inevitable mechanical injury and may recover its phytoremediation effect.

Advances in Microgravity Directed Tissue Engineering

Tissue engineering aims to generate functional biological substitutes to repair, sustain, improve, or replace tissue function affected by disease. With the rapid development of space science, the application of simulated microgravity has become an active topic in the field of tissue engineering. There is a growing body of evidence demonstrating that microgravity offers excellent advantages for tissue engineering by modulating cellular morphology, metabolism, secretion, proliferation, and stem cell differentiation. To date, there have been many achievements in constructing bioartificial spheroids, organoids, or tissue analogs with or without scaffolds in vitro under simulated microgravity conditions. Herein, the current status, recent advances, challenges, and prospects of microgravity related to tissue engineering are reviewed. Current simulated-microgravity devices and cutting-edge advances of microgravity for biomaterials-dependent or biomaterials-independent tissue engineering to offer a reference for guiding further exploration of simulated microgravity strategies to produce engineered tissues are summarized and discussed.

Effects of neodymium magneto-priming on seed germination and salinity tolerance in tomato

Earth's biosphere is surrounded by magnetic fields that affect all living organisms. A plant's response to magnetic fields is displayed in terms of its seed's vigor, growth, and yield. Examining seed germination in such magnetic fields is the first step in the investigation of how magnetic fields might be used to enhance plant growth and maximize crop performance. In this study, salinity-sensitive Super Strain-B tomato seeds were primed with the northern and southern poles of neodymium magnets of 150, 200, and 250 mT. The magneto-primed seeds showed a significant increase in germination rate and speed, where the orientation of the magnet was identified as being crucial for germination rate and the orientation of seeds towards the magnet was shown to affect the germination speed. The primed plants exhibited enhanced growth characteristics, including longer shoots and roots, larger leaf area, more root hairs, higher water content, and more tolerance to salinity levels, up to 200 mM NaCl. All magneto-primed plants showed a significant decrease in chlorophyll content, continuous chlorophyll fluorescence yield (Ft), and quantum yield (QY). The salinity treatments decreased all chlorophyll parameters in control plants, significantly, but did not lower such parameters in magneto-primed tomatoes. The results of this study illustrate the positive effects of neodymium magnet on the growth and development of tomato plants in terms of their germination, growth, and salinity tolerance, and negatively affected the chlorophyll content in tomato leaves. © 2023 Bioelectromagnetics Society.

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.

The Static Magnetic Field Regulates the Structure, Biochemical Activity, and Gene Expression of Plants

The purpose of this paper is to review the scientific results and summarise the emerging topic of the effects of statistic magnetic field on the structure, biochemical activity, and gene expression of plants. The literature on the subject reports a wide range of possibilities regarding the use of the magnetic field to modify the properties of plant cells. MFs have a significant impact on the photosynthesis efficiency of the biomass and vigour accumulation indexes. Treating plants with SMFs accelerates the formation and accumulation of reactive oxygen species. At the same time, the influence of MFs causes the high activity of antioxidant enzymes, which reduces oxidative stress. SMFs have a strong influence on the shape of the cell and the structure of the cell membrane, thus increasing their permeability and influencing the various activities of the metabolic pathways. The use of magnetic treatments on plants causes a higher content of proteins, carbohydrates, soluble and reducing sugars, and in some cases, lipids and fatty acid composition and influences the uptake of macro- and microelements and different levels of gene expression. In this study, the effect of MFs was considered as a combination of MF intensity and time exposure, for different varieties and plant species. The following article shows the wide-ranging possibilities of applying magnetic fields to the dynamics of changes in the life processes and structures of plants. Thus far, the magnetic field is not widely used in agricultural practice. The current knowledge about the influence of MFs on plant cells is still insufficient. It is, therefore, necessary to carry out detailed research for a more in-depth understanding of the possibilities of modifying the properties of plant cells and achieving the desired effects by means of a magnetic field.

The Effect on the Germination Vigour of Cucumber Seeds after Receiving Magnetic Field Treatment Pre-Sowing

In the experiment, the impact of magnetisation on cucumber seeds is examined with the use of Bitter magnets with a constant magnetic field. The magnetisation process is performed in three magnetic fields: low—200 mT, medium—1 T, and high—9 T for 15 and 60 min. After germination, the biometric parameters are determined. The results of this research show that cucumber after pre-treatment in a magnetic field of 1 T for 60 min has a similar germination capacity and root length as the control sample. However, cucumber seeds magnetised in a 1 T field for 60 min have a significantly higher dry weight than the control sample (5.50 ± 0.32 mg vs. 3.01 ± 0.18 mg). The magnetisation in 9 T for both 15 and 60 min shows that these samples have a significantly lower germination capacity (86.8 ± 4.4% and 81.4 ± 7.3% vs. 91.8 a ± 3.2%) and root length (1.78 ± 0.02 cm and 4.42 ± 0.83 cm vs. 8.21 ± 0.34 cm) compared to the control sample. The cucumber seeds pre-treated at 9 T have a significantly greater dry weight than the control sample. Additionally, our research shows that some magnetic field intensities and magnetisation durations inhibit root growth and limit germination. These results are also important as they indicate which values of magnetic fields should be avoided.

Effect of Magnetic and Electrical Fields on Yield, Shelf Life and Quality of Fruits

The presented article is a review of the literature reports on the influence of magnetic and electric fields on the growth, yield, ripening, and durability of fruits and their quality. The article shows the potential application of MF and EF in agricultural production. Magnetic and electrical fields increase the shelf life of the fruit and improve its quality. Alternating magnetic fields (AMF) with a value of 0.1–200 mT and a power frequency of 50 Hz or 60 Hz improve plant growth parameters. MF cause an increase in firmness, the rate of maturation, the content of beta-carotene, lycopene, and fructose, sugar concentration, and a reduction in acidity and respiration. The most common is a high-voltage electric field (HVEF) of 2–3.61 kV/cm. These fields extend the shelf life and improve the quality of fruit by decreasing respiration rate and ethylene production. The presented methods seem to be a promising way to increase the quantity and quality of crops in agricultural and fruit production. They are suitable for extending the shelf life of fruit and vegetables during their storage. Further research is needed to develop an accessible and uncomplicated way of applying MF and AEF in agricultural and fruit production.

Effect of using Celosia argentea grown from seeds treated with a magnetic field to conduct Cd phytoremediation in drought stress conditions

The mechanisms of the stimulatory effect of external magnetic fields on plant growth have been revealed; however, the role of magnetic fields in the efficiency of phytoremediation with Celosia argentea grown under drought stress which results in detrimental influences on food security has not been reported. Therefore, this study evaluated the physiological responses of C. argentea to the interactions between exposure to a magnetic field and drought stress. Compared with a control, a drought treatment negatively affected the dry weight, transpiration rate, and Cd extraction efficiency of the species and caused oxidative damage in plant cells, as manifested by the increase in malondialdehyde levels and antioxidant enzyme activities. The biomass production, pigment levels, Cd content, and phytoremediation efficiency of the plant were positively affected by all magnetic field treatments compared to the control. All magnetic treatments, except those at 30 mT, alleviated the detrimental effects induced by a 10-day irrigation regime by enhancing the dry weight, chlorophyll content, and activities of antioxidant enzymes in the leaves of the plant. In terms of the interaction between pre-sowing magnetic field seed treatment and drought stress, a 100 mT treatment increased most of the measured parameters, particularly under a 3-day irrigation regime; this corresponded to the optimal phytoremediation efficiency. The results suggest that magnetic field treatment is a novel, economical, and practicable strategy by which to increase the efficiency of phytoremediation using C. argentea under drought stress.

Differential root and shoot magnetoresponses in Arabidopsis thaliana

The geomagnetic field (GMF) is one of the environmental stimuli that plants experience continuously on Earth; however, the actions of the GMF on plants are poorly understood. Here, we carried out a time-course microarray experiment to identify genes that are differentially regulated by the GMF in shoot and roots. We also used qPCR to validate the activity of some genes selected from the microarray analysis in a dose-dependent magnetic field experiment. We found that the GMF regulated genes in both shoot and roots, suggesting that both organs can sense the GMF. However, 49% of the genes were regulated in a reverse direction in these organs, meaning that the resident signaling networks define the up- or downregulation of specific genes. The set of GMF-regulated genes strongly overlapped with various stress-responsive genes, implicating the involvement of one or more common signals, such as reactive oxygen species, in these responses. The biphasic dose response of GMF-responsive genes indicates a hormetic response of plants to the GMF. At present, no evidence exists to indicate any evolutionary advantage of plant adaptation to the GMF; however, plants can sense and respond to the GMF using the signaling networks involved in stress responses.

Enhancement of the denitrification performance of an activated sludge using an electromagnetic field in batch mode

The influence of electromagnetic fields on bacterial denitrification has been tested on synthetic media with sludges from wastewater treatment stations, in batch mode. The effects of the intensity of the magnetic induction ratio B (mT), reaction volume and initial biomass concentration on the kinetics of the denitrification process were studied. Magnetic field had both an optimal stimulating effect on the activity of the denitrifying flora for B (mT)/mgx values of the order of 0.212, and an inhibitory effect for the values beyond the latter.Sludges underwent multiple exposure cycles to magnetic fields. It was shown that, after three exposure cycles, denitrification kinetics went from 6.5 to 12.7 mg N-NO^-₃.L^-1.h^-1 which corresponds to a 2.7 fold improvement. The improved performance persists even after the cessation of the magnetic field. Observation of the sludge by the environmentalelectron microscope shows that the microbial population forming the starting sludge; changed following exposure to the magnetic field. The action of the; electromagnetic field on the microbial populations in denitrification resulted in the modification of the diversity of the flora that is initially present, favoring the development of Proteo bacteria, particularly the Betaproteo bacteria subclass, which results in improved denitrification.

Exploration of space to achieve scientific breakthroughs

Living organisms adapt to changing environments using their amazing flexibility to remodel themselves by a process called evolution. Environmental stress causes selective pressure and is associated with genetic and phenotypic shifts for better modifications, maintenance, and functioning of organismal systems. The natural evolution process can be used in complement to rational strain engineering for the development of desired traits or phenotypes as well as for the production of novel biomaterials through the imposition of one or more selective pressures. Space provides a unique environment of stressors (e.g., weightlessness and high radiation) that organisms have never experienced on Earth. Cells in the outer space reorganize and develop or activate a range of molecular responses that lead to changes in cellular properties. Exposure of cells to the outer space will lead to the development of novel variants more efficiently than on Earth. For instance, natural crop varieties can be generated with higher nutrition value, yield, and improved features, such as resistance against high and low temperatures, salt stress, and microbial and pest attacks. The review summarizes the literature on the parameters of outer space that affect the growth and behavior of cells and organisms as well as complex colloidal systems. We illustrate an understanding of gravity-related basic biological mechanisms and enlighten the possibility to explore the outer space environment for application-oriented aspects. This will stimulate biological research in the pursuit of innovative approaches for the future of agriculture and health on Earth.

A novel phytoremediation method assisted by magnetized water to decontaminate soil Cd based on harvesting senescent and dead leaves of Festuca arundinacea

It is more economical and feasible to harvest above-ground plant tissues, especially leaves, than to uproot the entire plant during phytoremediation. The major goal of this study is to estimate the promoting effect of an external magnetic field on soil Cadmium (Cd) remediation efficiency by harvesting the leaves of Festuca arundinacea, irrigated by normal and magnetized water. Changes in the amount of emerging, mature, senescent, and dead leaves, as well as Cd concentrations in the corresponding tissues were compared. It was found that F. arundinacea irrigated by either kind of water accumulated significantly more Cd in senescent and dead leaves than in other tissues. After irrigation with magnetized water, the biomass of senescent and dead leaves increased from 15.7 and 6.4% to 17.2 and 11.6%, respectively, and a significantly higher amount of Cd (˜23.6%) was redistributed into dead leaves compared with the control. Thus, significantly more Cd was removed by harvesting the senescent and dead leaves of F. arundinacea. These results indicate that magnetic fields can increase the phytoremediation efficiency of F. arundinacea for Cd, and simultaneously reduce the cost of harvested residue disposal.

Comparison of Microgravity Analogs to Spaceflight in Studies of Plant Growth and Development

Life on Earth has evolved under the influence of gravity. This force has played an important role in shaping development and morphology from the molecular level to the whole organism. Although aquatic life experiences reduced gravity effects, land plants have evolved under a 1-g environment. Understanding gravitational effects requires changing the magnitude of this force. One method of eliminating gravity''s influence is to enter into a free-fall orbit around the planet, thereby achieving a balance between centripetal force of gravity and the centrifugal force of the moving object. This balance is often mistakenly referred to as microgravity, but is best described as weightlessness. In addition to actually compensating gravity, instruments such as clinostats, random-positioning machines (RPM), and magnetic levitation devices have been used to eliminate effects of constant gravity on plant growth and development. However, these platforms do not reduce gravity but constantly change its direction. Despite these fundamental differences, there are few studies that have investigated the comparability between these platforms and weightlessness. Here, we provide a review of the strengths and weaknesses of these analogs for the study of plant growth and development compared to spaceflight experiments. We also consider reduced or partial gravity effects via spaceflight and analog methods. While these analogs are useful, the fidelity of the results relative to spaceflight depends on biological parameters and environmental conditions that cannot be simulated in ground-based studies.

Static magnetic field regulates Arabidopsis root growth via auxin signaling

Static magnetic field (SMF) plays important roles in biological processes of many living organisms. In plants, however, biological significance of SMF and molecular mechanisms underlying SMF action remain largely unknown. To address these questions, we treated Arabidopsis young seedlings with different SMF intensities and directions. Magnetic direction from the north to south pole was adjusted in parallel (N0) with, opposite (N180) and perpendicular to the gravity vector. We discovered that root growth is significantly inhanced by 600 mT treatments except for N180, but not by any 300 mT treatments. N0 treatments lead to more active cell division of the meristem, and higher auxin content that is regulated by coordinated expression of PIN3 and AUX1 in root tips. Consistently, N0-promoted root growth disappears in pin3 and aux1 mutants. Transcriptomic and gene ontology analyses revealed that in roots 85% of the total genes significantly down-regulated by N0 compared to untreatment are enriched in plastid biological processes, such as metabolism and chloroplast development. Lastly, no difference in root length is observed between N0-treated and untreated roots of the double cryptochrome mutant cry1 cry2. Taken together, our data suggest that SMF-regulated root growth is mediated by CRY and auxin signaling pathways in Arabidopsis.

Magnetic field enhance decontamination efficiency of Noccaea caerulescens and reduce leaching of non-hyperaccumulated metals

Hyperaccumulators can accumulate high amounts of specific metals and have been widely used to remediate metal polluted soil. However, organic acid secretion and soil acidification (two important mechanisms for hyperaccumulators to mobilize and extract metals) can also activate non-hyperaccumulated metals and then increase the leaching risk. The decontamination efficiency and leaching risk of using Noccaea caerulescens (formerly Thlaspi caerulescens) and Thlaspi arvense were compared in the present study. Although N. caerulescens accumulated significantly more Cd and Zn than T. arvense, it increased the leaching risk of Pb and Cu as well. Under magnetic fields of 30, 60, 120 and 150 mT, the biomass production of N. caerulescens was increased by 18.5, 48.9, 80.4, and 29.3% respectively, but decreased by 21.7% under 400 mT. Comparing with the control, plants raised from seeds pre-treated by magnetic fields accumulated 37.8-250.1% more metals and reduced the leachate volume and leached metals by 1.1-32.9% and 4.6-48.1% respectively. Considering remediation efficiency, environmental risk alleviation and energy consumption, N. caerulescens treated by 120 mT magnetic field is suited to remediate multi-metal polluted soil.

Effects of weak static magnetic fields on the gene expression of seedlings of Arabidopsis thaliana

Magnetic-field reception of animals and plants is currently discussed in the framework of a cryptochrome-based radical-pair mechanism. Efforts to unravel magnetoreception in plants suffered historically from several shortcomings, most prominently, the conspicuous absence of detailed stimulus-response relationships. To determine the sensitivity of seedlings of Arabidopsis thaliana to weak static magnetic fields we generated stimulus-response curves between near zero and 188 μT for the transcript levels of the genes rbcl, cab4, pal4 and ef1. The moderate magneto-responsiveness of dark-grown seedlings was greatly enhanced under blue light, and for rbcl and pal4 also under red light. The stimulus-response curves obtained under blue light of constant photon-fluence rate displayed multiple maxima and thus a pattern fundamentally different from that prevalent in plant and animal physiology. A double mutant lacking cryptochromes 1 and 2 displayed altered stimulus-response curves without losing, however, magneto-responsiveness completely. A reversal of the magnetic field direction substantially affected the gene expression and the quantity of CAB-protein (chlorophyll a,b-binding protein). The majority of our results are at variance with the notion of cryptochromes acting as the only magnetic-field sensors. They do not, however, exclude the possibility that cryptochromes participate in the magnetic field reception of Arabidopsis. The findings have the unexpected implication that cryptochrome- and phytochrome-mediated plant responses can be modulated by the strength and the orientation of the local geomagnetic field.

Effect of magnetic field on in vitro seedling growth and shoot regeneration from cotyledon node explants of Lathyrus chrysanthus boiss

The stimulatory effects on germination of seeds and growth of plants of static magnetic field (MF) pre-treatments depending on MF intensity, exposure time periods, signal form, flux density, and source frequencies on plants are reported. Seed germination frequency is low due to dormancy in Lathyrus chrysanthus Boiss. from Fabaceae family, consisting of 187 taxa. Tissue culture protocol for this plant has already been optimized. This plant is also used as a model for developing alternative methods to overcome dormancy. This study was conducted to determine the effects of MF on in vitro seed germination, seedling growth, and shoot regeneration capacity of cotyledon node explants in Lathyrus chrysanthus Boiss. to obtain healthy seedlings in large quantities. The seeds of an ecotype (Diyarbakir) were subjected to 125 mT MF strength for different exposure time periods (0-untreated, 24, 48, and 72 h). Sterilized seeds were germinated on growth basal medium in Magenta vessels. Seed germination and seedling growth percentages were recorded after 7 and 14 days of culture initiation, whereas seedling and root lengths were noted 28 days after culture initiation. At the end of the culture, shoot regeneration percentage, shoot number per explant, highest shoot height per explant, and total shoot number per petri dish were recorded. According to the results, it could be concluded that MF treatment could clearly be used to improve germination by breaking dormancy not only in Lathyrus chrysanthus Boiss. but also other plant species. Bioelectromagnetics. 39:547-555, 2018.© 2018 Wiley Periodicals, Inc.

Possible role of iron containing proteins in physiological responses of soybean to static magnetic field

Iron is a component of many proteins that have crucial roles in plant growth and development, such as ferritin and catalase. Iron also, as a ferromagnetic element, is assumed to be influenced by a static magnetic field (SMF). In the present study, we examined the relationship between ferrous content and gene expression and activity of ferritin and catalase in soybean plants under the influence of 0, 20, and 30 mT SMF for 5 day, 5 h each. Exposure to 20 mT decreased gene expression of Fe transporter, ferrous and H2O2 contents and gene expression, content and activity of ferritin and catalase. Opposite responses were observed under 30 mT treatments. The results suggest that SMF triggered a signaling pathway that is mediated by iron. The structure and activity of purified ferritin and apoferritin from horse spleen, and catalase from bovine liver proteins under SMF were evaluated as well. Secondary structure of proteins were not influenced by SMF (evidenced by far-UV circular dichroism), whereas their tertiary structure, size, and activity were altered (shown by fluorescence spectroscopy and dynamic light-scattering). From these results, it is likely that the number of iron atoms is involved in the nature of influence of SMF on protein structure.

Toward 20 T magnetic resonance for human brain studies: opportunities for discovery and neuroscience rationale

An initiative to design and build magnetic resonance imaging (MRI) and spectroscopy (MRS) instruments at 14 T and beyond to 20 T has been underway since 2012. This initiative has been supported by 22 interested participants from the USA and Europe, of which 15 are authors of this review. Advances in high temperature superconductor materials, advances in cryocooling engineering, prospects for non-persistent mode stable magnets, and experiences gained from large-bore, high-field magnet engineering for the nuclear fusion endeavors support the feasibility of a human brain MRI and MRS system with 1 ppm homogeneity over at least a 16-cm diameter volume and a bore size of 68 cm. Twelve neuroscience opportunities are presented as well as an analysis of the biophysical and physiological effects to be investigated before exposing human subjects to the high fields of 14 T and beyond.

Magnetic fields: how is plant growth and development impacted?

This review provides detailed insight on the effects of magnetic fields on germination, growth, development, and yield of plants focusing on ex vitro growth and development and discussing the possible physiological and biochemical responses. The MFs considered in this review range from the nanoTesla (nT) to geomagnetic levels, up to very strong MFs greater than 15 Tesla (T) and also super-weak MFs (near 0 T). The theoretical bases of the action of MFs on plant growth, which are complex, are not discussed here and thus far, there is limited mathematical background about the action of MFs on plant growth. MFs can positively influence the morphogenesis of several plants which allows them to be used in practical situations. MFs have thus far been shown to modify seed germination and affect seedling growth and development in a wide range of plants, including field, fodder, and industrial crops; cereals and pseudo-cereals; grasses; herbs and medicinal plants; horticultural crops (vegetables, fruits, ornamentals); trees; and model crops. This is important since MFs may constitute a non-residual and non-toxic stimulus. In addition to presenting and summarizing the effects of MFs on plant growth and development, we also provide possible physiological and biochemical explanations for these responses including stress-related responses of plants, explanations based on dia-, para-, and ferromagnetism, oriented movements of substances, and cellular and molecular changes.

Use of high gradient magnetic fields to evaluate gravity perception and response mechanisms in plants and algae

Magnetic gradients have the valuable property of exerting a repulsive ponderomotive force onto diamagnetic compounds. A carefully designed gradient and proper positioning of biological material can be used to manipulate gravisensing organelles such as amyloplasts of higher plants and other statoliths such as the BaSO4-filled vesicles of Characean algae. This chapter describes the main considerations of magnetic gradients and their application as a localized force field to manipulate (sort) cellular organelles based on their magnetic properties. Many of the inferences from such activities have yet to be investigated.

Mechanisms of disruption of meristematic competence by microgravity in Arabidopsis seedlings

Experiments performed in actively proliferating plant cells both in space and simulated microgravity have evidenced a common effect: cell proliferation appears enhanced whereas cell growth is depleted. Coordination of cell growth and proliferation, called meristematic competence, is a major feature of meristematic cells and its disruption may lead to important alterations in the developmental pattern of the plant. Auxin is known to be a mediator of the transduction of the gravitropic signal and a regulator of the rates of growth and proliferation in meristematic cells, as well as of their further differentiation. Therefore, gravity sensing, gravitropism, auxin levels, and meristematic competence are mutually interrelated. However, our experiments in simulated microgravity, using both mechanical and magnetic levitation technologies, have revealed that this interdependence is neither strict nor univocal and may include additional factors and mechanisms. Available data indicate that altered gravity may affect cell growth and proliferation by mechanisms alternative to the transduction of the gravitropic signal perceived by columella cells in the root tip. These mechanisms would include gravity sensing independent from statolith displacement and transduction mediators other than polar auxin transport.

Cell proliferation and plant development under novel altered gravity environments

Gravity is a key factor for life on Earth. It is the only environmental factor that has remained constant throughout evolution, and plants use it to modulate important physiological activities; gravity removal or alteration produces substantial changes in essential functions. For root gravitropism, gravity is sensed in specialised cells, which are capable of detecting magnitudes of the g vector lower than 10(-3) . Then, the mechanosignal is transduced to upper zones of the root, resulting in changes in the lateral distribution of auxin and in the rate of auxin polar transport. Gravity alteration has consequences for cell growth and proliferation rates in root meristems, which are the basis of the developmental programme of a plant, in which regulation via auxin is involved. The effect is disruption of meristematic competence, i.e. the strict coordination between cell proliferation and growth, which characterises meristematic cells. This effect can be related to changes in the transport and distribution of auxin throughout the root. However, similar effects of gravity alteration have been found in plant cell cultures in vitro, in which neither specialised structures for gravity sensing and signal transduction, nor apparent gravitropism have been described. We postulate that gravity resistance, a general mechanism of cellular origin for developing rigid structures in plants capable of resisting the gravity force, could also be responsible for the changes in cell growth and proliferation parameters detected in non-specialised cells. The mechanisms of gravitropism and graviresistance are complementary, the first being mostly sensitive to the direction of the gravity vector, and the second to its magnitude. At a global molecular level, the consequence of gravity alteration is that the genome should be finely tuned to counteract a type of stress that plants have never encountered before throughout evolution. Multigene families and redundant genes present an advantage in that they can experience changes without the risk of being deleterious and, for this reason, they should play a key role in the response to gravitational stress.

Magnetic field effects on plant growth, development, and evolution

The geomagnetic field (GMF) is a natural component of our environment. Plants, which are known to sense different wavelengths of light, respond to gravity, react to touch and electrical signaling, cannot escape the effect of GMF. While phototropism, gravitropism, and tigmotropism have been thoroughly studied, the impact of GMF on plant growth and development is not well-understood. This review describes the effects of altering magnetic field (MF) conditions on plants by considering plant responses to MF values either lower or higher than those of the GMF. The possible role of GMF on plant evolution and the nature of the magnetoreceptor is also discussed.

MRI of plants and foods

The importance and prospects for MRI as applied to intact plants and to foods are presented in view of one of humanity's most pressing concerns, the sustainable and healthy feeding of a worldwide increasing population. Intact plants and foods have in common that their functionality is determined by complex multiple length scale architectures. Intact plants have an additional level of complexity since they are living systems which critically depend on transport and signalling processes between and within tissues and organs. The combination of recent cutting-edge technical advances and integration of MRI accessible parameters has the perspective to contribute to breakthroughs in understanding complex regulatory plant performance mechanisms. In food science and technology MRI allows for quantitative multi-length scale structural assessment of food systems, non-invasive monitoring of heat and mass transport during shelf-life and processing, and for a unique view on food properties under shear. These MRI applications are powerful enablers of rationally (re)designed food formulations and processes. Limitations and bottlenecks of the present plant and food MRI methods are mainly related to short T2 values and susceptibility artefacts originating from small air spaces in tissues/materials. We envisage cross-fertilisation of solutions to overcome these hurdles in MRI applications in plants and foods. For both application areas we witness a development where MRI is moving from highly specialised equipment to mobile and downscaled versions to be used by a broad user base in the field, greenhouse, food laboratory or factory.

Spaceflight engages heat shock protein and other molecular chaperone genes in tissue culture cells of Arabidopsis thaliana

PREMISE OF THE STUDY

Gravity has been a major force throughout the evolution of terrestrial organisms, and plants have developed exquisitely sensitive, regulated tropisms and growth patterns that are based on the gravity vector. The nullified gravity during spaceflight allows direct assessment of gravity roles. The microgravity environments provided by the Space Shuttle and International Space Station have made it possible to seek novel insights into gravity perception at the organismal, tissue, and cellular levels. Cell cultures of Arabidopsis thaliana perceive and respond to spaceflight, even though they lack the specialized cell structures normally associated with gravity perception in intact plants; in particular, genes for a specific subset of heat shock proteins (HSPs) and factors (HSFs) are induced. Here we ask if similar changes in HSP gene expression occur during nonspaceflight changes in gravity stimulation.

METHODS

Quantitative RT-qPCR was used to evaluate mRNA levels for Hsp17.6A and Hsp101 in cell cultures exposed to four conditions: spaceflight (mission STS-131), hypergravity (centrifugation at 3 g or 16 g), sustained two-dimensional clinorotation, and transient milligravity achieved on parabolic flights.

KEY RESULTS

We showed that HSP genes were induced in cells only in response to sustained clinorotation. Transient microgravity intervals in parabolic flight and various hypergravity conditions failed to induce HSP genes.

CONCLUSIONS

We conclude that nondifferentiated cells do indeed sense their gravity environment and HSP genes are induced only in response to prolonged microgravity or simulated microgravity conditions. We hypothesize that HSP induction upon microgravity indicates a role for HSP-related proteins in maintaining cytoskeletal architecture and cell shape signaling.

Analysis of magnetic gradients to study gravitropism

PREMISE OF THE STUDY

Gravitropism typically is generated by dense particles that respond to gravity. Experimental stimulation by high-gradient magnetic fields provides a new approach to selectively manipulate the gravisensing system.

METHODS

The movement of corn, wheat, and potato starch grains in suspension was examined with videomicroscopy during parabolic flights that generated 20 to 25 s of weightlessness. During weightlessness, a magnetic gradient was generated by inserting a wedge into a uniform, external magnetic field that caused repulsion of starch grains. The resultant velocity of movement was compared with the velocity of sedimentation under 1 g conditions.

RESULTS

The high-gradient magnetic fields repelled the starch grains and generated a force of at least 0.6 g. Different wedge shapes significantly affected starch velocity and directionality of movement.

CONCLUSIONS

Magnetic gradients are able to move diamagnetic compounds under weightless or microgravity conditions and serve as directional stimulus during seed germination in low-gravity environments. Further work can determine whether gravity sensing is based on force or contact between amyloplasts and statocyte membrane system.

Effects of pulsed magnetic field treatment of soybean seeds on calli growth, cell damage, and biochemical changes under salt stress

The effects of magnetic field (MF) treatments of soybean seeds on calli growth, cell damage, and biochemical changes under salt stress were investigated under controlled conditions. Soybean seeds were exposed to a 1.0 Hz sinusoidal uniform pulsed magnetic field (PMF) of 1.5 µT for 5 h/day for 20 days. Non-treated seeds were considered as controls. For callus regeneration, the embryonic axis explants were taken from seeds and inoculated in a saline medium with a concentration of 10 mM NaCl for calli growth analysis and biochemical changes. The combined treatment of MF and salt stress was found to significantly increase calli fresh weight, total soluble sugar, total protein, and total phenol contents, but it decreased the ascorbic acid, lipid peroxidation, and catalase activity of calli from magnetically exposed seeds compared to the control calli. PMF treatment significantly improved calli tolerance to salt stress in terms of an increase in flavonoid, flavone, flavonole, alkaloid, saponin, total polyphenol, genistein, and daidzein contents under salt stress. The results suggest that PMF treatment of soybean seeds has the potential to counteract the adverse effects of salt stress on calli growth by improving primary and secondary metabolites under salt stress conditions.

Surveying the plant's world by magnetic resonance imaging

Understanding the way in which plants develop, grow and interact with their environment requires tools capable of a high degree of both spatial and temporal resolution. Magnetic resonance imaging (MRI), a technique which is able to visualize internal structures and metabolites, has the great virtue that it is non-invasive and therefore has the potential to monitor physiological processes occurring in vivo. The major aim of this review is to attract plant biologists to MRI by explaining its advantages and wide range of possible applications for solving outstanding issues in plant science. We discuss the challenges and opportunities of MRI in the study of plant physiology and development, plant-environment interactions, biodiversity, gene functions and metabolism. Overall, it is our view that the potential benefit of harnessing MRI for plant research purposes is hard to overrate.

Gravitational and magnetic field variations synergize to cause subtle variations in the global transcriptional state of Arabidopsis in vitro callus cultures

BACKGROUND

Biological systems respond to changes in both the Earth's magnetic and gravitational fields, but as experiments in space are expensive and infrequent, Earth-based simulation techniques are required. A high gradient magnetic field can be used to levitate biological material, thereby simulating microgravity and can also create environments with a reduced or an enhanced level of gravity (g), although special attention should be paid to the possible effects of the magnetic field (B) itself.

RESULTS

Using diamagnetic levitation, we exposed Arabidopsis thaliana in vitro callus cultures to five environments with different levels of effective gravity and magnetic field strengths. The environments included levitation, i.e. simulated μg* (close to 0 g* at B = 10.1 T), intermediate g* (0.1 g* at B = 14.7 T) and enhanced gravity levels (1.9 g* at B = 14.7 T and 2 g* at B = 10.1 T) plus an internal 1 g* control (B = 16.5 T). The asterisk denotes the presence of the background magnetic field, as opposed to the effective gravity environments in the absence of an applied magnetic field, created using a Random Position Machine (simulated μg) and a Large Diameter Centrifuge (2 g).Microarray analysis indicates that changes in the overall gene expression of cultured cells exposed to these unusual environments barely reach significance using an FDR algorithm. However, it was found that gravitational and magnetic fields produce synergistic variations in the steady state of the transcriptional profile of plants. Transcriptomic results confirm that high gradient magnetic fields (i.e. to create μg* and 2 g* conditions) have a significant effect, mainly on structural, abiotic stress genes and secondary metabolism genes, but these subtle gravitational effects are only observable using clustering methodologies.

CONCLUSIONS

A detailed microarray dataset analysis, based on clustering of similarly expressed genes (GEDI software), can detect underlying global-scale responses, which cannot be detected by means of individual gene expression techniques using raw or corrected p values (FDR). A subtle, but consistent, genome-scale response to hypogravity environments was found, which was opposite to the response in a hypergravity environment.

Gene expression profile in cultured human umbilical vein endothelial cells exposed to a 300 mT static magnetic field

In a previous investigation we reported that exposure to a moderate (300 mT) static magnetic field (SMF) causes transient DNA damage and promotes mitochondrial biogenesis in human umbilical vein endothelial cells (HUVECs). To better understand the response of HUVECs to the 300 mT SMF, a high-quality subtracted cDNA library representative of genes induced in cells after 4 h of static magnetic exposure was constructed. The global gene expression profile showed that several genes were induced after the SMF exposure. The characterized clones are involved in cell metabolism, energy, cell growth/division, transcription, protein synthesis, destination and storage, membrane injury, DNA damage/repair, and oxidative stress response. Quantitative real-time polymerase chain reaction (qRT-PCR) experiments were performed at 4 and 24 h on four selected genes. Their expression profiles suggest that HUVEC's response to SMF exposure is transient. Furthermore, compared to control cells, an up-regulation of several genes involved in cell growth and division was observed. This up-regulation is likely to be the cause of the slight, but significant, increase in cell proliferation at 12 h post-treatment. These results provide additional support to the notion that SMFs may be harmless to human health, and could support the rationale for their possible use in medical treatments.

Exposure to high static or pulsed magnetic fields does not affect cellular processes in the yeast Saccharomyces cerevisiae

We report results of a study of the effects of strong static (up to 16 T for 8 h) and pulsed (up to 55 T single-shot and 4 x 20 T repeated shots) magnetic fields on Saccharomyces cerevisiae cultures in the exponential phase of growth. In contrast to previous reports restricted to only a limited number of cellular parameters, we have examined a wide variety of cellular processes: genome-scale gene expression, proteome profile, cell viability, morphology, and growth, metabolic and fermentation activity after magnetic field exposure. None of these cellular activities were impaired in response to static or pulsed magnetic field exposure. Our results confirm and extend previous reports on the absence of magnetic field effects on yeast and support the hypothesis that magnetic fields have no impact on the transcriptional machinery and on the integrity of unicellular biological systems.

Diamagnetic levitation changes growth, cell cycle, and gene expression of Saccharomyces cerevisiae

Inhomogeneous magnetic fields are used in magnetic traps to levitate biological specimens by exploiting the natural diamagnetism of virtually all materials. Using Saccharomyces cerevisiae, this report investigates whether magnetic field (B) induces changes in growth, cell cycle, and gene expression. Comparison to the effects of gravity and temperature allowed determination of whether the responses are general pathways or stimulus specific. Growth and cell cycle analysis were examined in wild-type (WT) yeast and strains with deletions in transcription factors Msn4 or Sfp1. Msn4, Sfp1, and Rap1 have been implicated in responses to physical forces, but only Msn4 and Sfp1 deletions are viable. Gene expression changes were examined in strains bearing GFP-tagged reporters for YIL052C (Sfp1-dependent), YST-2 (Sfp1/Rap1-dependent), or SSA4 (Msn4-dependent). The cell growth and gene expression responses were highly stimulus specific. B increased growth only following Msn4 or Sfp1 deletion, associated with decreased G1 and G2/M and increased S phase of the cell cycle. In addition, B suppressed expression of both YIL052C and YST2. Gravity decreased growth in an Sfp1 but not Msn4-dependent manner, in association with decreased G2/M and increased S phase of the cell cycle. Additionally, gravity decreased expression of SSA4 and YIL052C genes. Temperature increased cell growth in an Msn4- and Sfp1-dependent manner in association with increased G1 and G2/M with decreased S phase of the cell cycle. In addition, temperature increased YIL052C gene expression. This study shows that B has selective effects on cell growth, cell cycle, and gene expression that are stimulus specific.