Microwave Treatment on Maize Seed Germination and Growth - Coursework Example

Microwave treatment on maize seed germination and growth Name Date Introduction Within the electromagnetic spectrum, there is the microwave part whose radiation frequency ranges from 300 MHz (300 million cycles per second) to 300 GHz (300 billion cycles per second). The electromagnetic waves in this band have a non-ionizing effect. According to Banik et al (2006: 822), this non-ionizing electromagnetic effect is absorbed at molecular level and manifests as changes in vibrational energy of heat or molecules. Studies have been conducted on different effects of various forms of externally applied electrical energy upon organisms and plants. Most of the work done describes microwave experiments using a frequency of 2450 MHz, which is among the frequencies allocated by international agreement to industrial and domestic microwave power devices. The exposure to microwave frequency fields has been increased by the extensive use of wireless telecommunication devices. These fields can be harmful depending on the duration of exposure, the power level, pulsed or continuous wave, frequency and the properties of exposed tissue. The exceptional impact of wireless mobile communication technology has presented a strong reason for present research in achieving comprehensive knowledge of the relationships between effects of microwave treatment on maize seed germination and growth and the physical variables (Ragha et al, 2011:168). Maize is a cereal crop that is grown in many parts across the world. Among all the grains, maize is the most produced grain annually. It is found in many colors and species. Maize was introduced in Africa in the sixteenth century and has since become one of the staple foods in the continent. As of today, it is the most crucial cereal crop in sub-Saharan Africa and a staple food for almost 1.5 billion people in Latin America and Africa. In developed countries, maize is commonly used as a raw material for industrial products and as livestock feed. Maize accounts for about 50% of low income earners in southern and eastern Africa. However, one should not rely to maize diet alone as it can lead to vitamin deficiency and malnutrition. Characteristics of microwave energy Microwaves form part of the electromagnetic spectrum and are therefore electromagnetic waves. Electromagnetic field is characterized by its energy content which is to its frequency by the equation: E = hf, where E = Electric field, h = plank’s constant and f = frequency. All waves within the electromagnetic spectrum comprise of electrical and magnetic field components that are mutually perpendicular and vibrate in phase (Macelloni et al, 1998:42). Electromagnetic waves differ depending on frequency. It is the very frequency that defines the characteristics of an electromagnetic wave. According to basic wave theory, the wavelength (λ) and frequency (f) are related by the equation: λ = c/f, where is the speed of light in vacuum. The two major components of a magnetic field are the magnetic flux (Φ) and the magnemotive force (F). Ampere’s law states that the total magnemotive force (F) integrated along any loop is equal to the total current enclosed that loop. There is a corresponding magnetic force whenever current is flowing. Magnetic force can be described by equipotential surfaces. These surfaces come to an end and are bound by the flow of current that gives rise to field. The magnetic field strength (H) is given by determine from the spacing between these equipotential surfaces. Magnetic flux lines always form closed loops that never overlap at any point. In any homogenous area, the magnetic flux lines are perpendicular to the equipotential surfaces of the magnetic force. The magnetic flux density (B) is determined by the spacing between the flux lines. The magnetic flux density B is related to magnetic field strength H by the following equation: B= µH, and µ = µ0µr, where µ0 is permeability in a vacuum (4πand µr is relative permeability. Ionizing and non-ionizing radiation EM waves are carried by particles known as quanta. The amount of energy carried by these particles is directly proportional to their frequencies. Electromagnetic waves with more energy per quanta have the ability to break the chemical bond of material they come in contact with. Radiations from electromagnetic waves with very high frequencies within the electromagnetic spectrum are classified as ionizing. Examples of this are X-rays and Gamma rays. Low frequency electromagnetic fields such as microwaves, radio waves, etc. produce non-ionization radiations (Macelloni et al, 1998:43). Specific Absorption Rate Specific absorption rate (SAR) is a calculated figure that is commonly used to describe the absorption of electromagnetic field in matter. It is the quantity of absorption of non-ionizing electromagnetic radiation by living tissue or cells. It is defined mathematically as the amount of energy per unit time (P) to the unit mass (m) of the living tissue. The interaction between plant microwaves and plant/living cells is a wide subject due to multiplicity of living cells and the physical occurrences that come into play. Each living cell has its own unique reaction when exposed to microwaves. These reactions depend on the duration of exposure, frequency of wave and intensity of exposure. Depending upon intensity and frequency, microwaves exposure may lead to breakdown or alteration of genetic or chemical link and may favor or inhibit cell growth. Radio frequency and microwave treatment of soil Many experiments have been conducted on the effect of radio frequencies on soil temperature (Davis et al, 1973: 132). In many occasions, a controlled and short exposure resulted in increased growth. However, extended exposure led to no germination at all as seeds died in the process. An earlier experiment was conducted on the application of microwave heating in soils of different moisture contents to kill the naturalized seed weeds in the soil samples (Barker and Craker, 1991: 303). The results obtained revealed that the susceptibility of a seed to microwave treatment entirely depends on temperature. When the temperature in the soil rose to 700C there was a drastic decline in the growth of natural weeds and they were completely wiped out with further increase in temperature. Experience obtained from early research affirms that a range of seed weeds in the soil can be killed by microwave treatment. The existence of explicit biological effects of microwave treatment on seed germination and growth still remains discussable. The idea that powerful microwave can produce thermal effects makes it technically hard to distinguish its probable explicit effect in experiments. (Dimitris and Margaritis, (2005: 36). According to Kazuhiko et al (1999: 12), the thermal impact of short microwave pulses, when hygienic limits are taken into account, cannot structurally or chemically affect the biological tissue and cells, even if the most detrimental assumption of 100% absorption is made. In addition, work done by Racuciu et al (2007: 648) reveal that there is no physical cause of any other effect other than the thermal effect. The real biochemical processes by which microwaves could affect the germination and growth of maize seeds are not very clear and the mechanism may vary depending on duty cycle, frequency and amplitude of the field. Researchers report that among various ways of pre-sowing treatment of seeds, special attention needs to be directed towards electromagnetic irradiation. The frequencies of the cell membrane radiations of biological specimens lie in the millimeter-wave range. The millimeter-wave irradiation of biological specimens kicks off resonant phenomena in living organisms and has a general constructive effect on biological objects. Various studies indicate that high power microwave can affect maize growth and the extended exposure to microwave affects germination of maize seeds. Aladjadjiyan, (2010: 108) records that microwaves determined variations in peroxidase and catalase activities in Zea mays depending on the age of the plants, the microwave exposure time and condition of seeds. It was indicated that plant growth was not affected by weak intensity but increased doses slowed down the germination process. Fischer et al, (2004:640) conducted an experiment on direct effect of electromagnetic radiation of the microwave on the germination and growth of cereals (maize, wheat, oats and barley). He used 1 cm wavelength and exposed them for forty minutes. There was an increased germination rate in all the tested seeds and the optimal effect was realized after twenty minutes exposure time. The use of microwave heating in agriculture It is a fact that seeds are heat sensitive and that seeds won’t germinate when exposed to too much heat. As put by Casada and Walton (1983:910), microwaves provide a faster heating mechanism as compared to traditional heating ovens thus excessive exposure of seeds to microwaves can lead to increases in seed temperature which may affects the seed’s viability or longevity. It is important to note that drying seeds at high temperatures may be detrimental to the seed because of the rapid removal of seed moisture which is supposed to help in cooling. Microwaves are mostly applied in domestic heating as compared to agricultural processing. However, its application in agriculture has increased in the recent past, for example in areas such as pest and weed control. It was suggested by Nelson (1987: 820) that uses of microwave heating in agriculture include seed treatment, drying, insect control, measurement of moisture content and product processing. He also suggested that mass production of magnetrons to serve as sources of energy for industrial and domestic microwave ovens has made the costs of energy sources to go down so that attention might be focused towards new applications of microwaves. In agriculture in general, and specifically in seed technology, seed moisture testing could be conducted by use of microwave heating. As examples, Okabe, et al (1973:62) used microwaves to improve germination of some tiny legume seeds, alfalfa, whose seed coats are naturally impermeable. He also used microwave in drying maize and ended up with promising results. Other successes were reported in controlling wood infesting insects thanks to microwaves. The work done by Murr (2004:115) indicates that microwaves are among the agents that stimulate seed growth. He argues that microwaves are bio-stimulators. The most common bio-stimulators are fertilizers that are made from chemicals. He studied the effect of magnetic fields from Helmholtz’s coil on germination and growth of soybean seeds. Microwave treatment of plants In controlling the growth of weeds, radio frequencies are not affected by wind which as major hindrance to conventional spraying methods. In addition, the microwave soil treatment can be directed an individual plant without affecting the adjacent plants. Furthermore, seeds and roots that are so deep in soil can also be killed by microwave energy. (Brodie et al, 2007: 325) The germination rate of maize seeds have been observed under different conditions ranging from natural environmental factors to other environmental synthetic factors. Several studies on the effect of electric fields on plants have been conducted. Some regions in the United Kingdom sometimes experience lethal dust storms which disturb the normal electrical balance of the atmosphere causing high electric field intensities to hover near the ground level. Jones (2001: 221) reports that crops were affected by electrical action whenever such storms occur. Other researchers have also realized detrimental effects on natural grass after storms. Due to such observations scholars have tried to investigate the chances of lethal electro tropism in cereal plants to the demonstrations that higher electric fields can stop the leaves from growing and/or kill the entire plant. Early research postulated that subjecting plants to microwave treatment was helpful. This topic has been debated and researched on for many years, but it has never been generally accepted as beneficial. From the mid sixteenth century to mid twentieth century, studies revealed that both vegetable and cereal crops could do better if they are exposed to microwave treatment while growing (Shibusawa and Shibata, 1970:2257; Jorgensen and Priestley, 2004: 342; Newman, 1971:915; Hendrick, 1998: 162). Various experiments were undertaken in late nineteenth century Lemstrom (2004:79) on effects of microwave treatment on plants in various places in Europe. Although his results were convincing, they were so inconsistent. He generally concluded that applying electromagnetic fields to plants by hanging conductors above them could produce healthy crops with increased yields. He conducted his experiments on cereals, vegetables and strawberries. He proposed that the optimum time for exposing microwaves to crops were for three hours in the early morning and another three hours in the evening. The microwaves could be exposed to plants all day in the case of cloudy weather and all nights of moist weather. Plants could be adversely affected by the microwave radiations in strong sunshine and during dry conditions. Lemstrom’s work was extended by several scholars. Generally the results that were obtained were encouraging. His trials with clover hay and maize in the twentieth century produced results that indicated increased yields. There was even the establishment of Electroculture Committee by the Board of Agriculture and Fisheries of the United Kingdom in 1918; nonetheless, its 1937 final report stated that the results obtained from their research were not decisive and that it was not obvious that plants benefited from electrical treatments (Board of Agriculture and Fisheries, 1918 – 1937). However, the European researchers did not share their encouraging results with their American counterparts, who tried but failed to realize significant and beneficial impact of microwave treatment on plant growth (Briggs et al, 2006:1379). In view of these findings and the unpredictability in the other results, confidence in the electrical treatment of plants was lost. The electrical approach failed to attract attention although in more recent work (Bachman, et al, 2001:500); interests have been shown in the effects of ions on plant growth. Murr (2004:118) suggested the term ‘lethal electro tropism’ following a number of studies on the impact of electromagnetic fields on crops. In his experiments, he established an electric field between two aluminium wires. He placed a lower electrode below the soil in a plot in which a maize seed was planted. The other electrode was suspended above the soil and was used in varying the electric field intensity by adjusting the gap between the electrode and soil but never went beyond 15 cm above the top of the soil. Light intensity and temperature were also controlled and the experiment sixteen hours. The plots used for control had similar electrode arrangement as the other electrodes even though no voltages were applied. The top electrode was made positive with respect to the bottom electrode which was connected to negative terminal of the power supply to excite the natural electric field of the earth (Chalmers, 2007: 184). It was observed that during unremitting exposure to electromagnetic fields, the leaves of the maize seedlings began to turn brown and similarity to mineral deficiency was noted. It also seemed that damage spread from the tip downwards at a rate faster than the plant’s growth. The researcher believed a probable cause of this detrimental effect was the migration of ionized minerals to the tip as a result of exposure to electromagnetic field. The concentration unbalance that comes with it might have a negative impact on the osmotic process and make cells to rapture. To further his investigation Murr (2004:119), applied field strengths of 25, 50 & 75 kV-1 to the maize seedlings. The results were contrary to expectation. There were no notable differences in the amounts of magnesium, nitrogen, potassium, calcium or phosphorus between the control and electrified samples. However, there was slight increase in minor elements: aluminium, zinc and iron. He concluded that the damaging effect was as a result of accelerated metabolism and general tissue deterioration and was not caused by movement of ionized salts and dehydration as he had thought initially. He associated the slight increase in minor elements with hastened ‘metallo-enzyme activity’ affecting respiration and damaging the issue in the end. According to him, accelerated metabolic reaction was also behind the changes in density of chloroplasts. The high densities of chloroplasts in treated leaves were due to the effect of ozone in oxidizing prophyrin groups. Earlier researchers had also reported deep green colour of leaves of plants exposed to static EM fields. Priestly (2010: 22) observed that wheat seedlings of wheat from electrified plots were darker green as compared to those in control plots. While furthering his experiments, he commented on the colour difference, stating that other investigators had noticed a darker green colour especially in wheat plant. While experimenting with oats, Blackman and Jorgensen (1987: 47) noted that, after 40 days the electrically treated crop was taller, greener and looked healthier than oats not exposed to electrical energy. Again in another study, Blackman (1994:243) observed that barley that was exposed to microwave radiations was greener and taller after one month than that in the adjacent control plot. A number of researchers have suggested that the increase in chlorophyll in cereal’s leaves might be as a result of continuous amounts of nitrates being added to the soil by the electrical apparatus. A soil test was conducted and it indicated about four times the amount of nitrogen in microwave treated soils than soil in control plots. Priestly, (2010:17) again postulated that plants exposed microwave radiations may directly make use of atmospheric nitrogen, perhaps by combination of carbohydrates within the plant and gaseous nitrogen. It was also observed by Hart and Schottenfield (2009: 412) that leaves of pole beans darkened when exposed to microwave radiations. However, extended exposure made plants to lose turgor and collapse. During the microwave treatment, damage in air was compared to that in hydrogen and nitrogen by passing them over the leaf during the treatment process. The damaging effect was large on the presence of hydrogen than air or nitrogen. Microwave remediation of contaminated soil Microwave-aided soil clean up has been applied to soils contaminated with volatile compounds. Microwave treatment has been so effective in soil remediation. Most constituents of the soil are transparent to microwaves and therefore the applied microwave radiation is concentrated on pore water and contaminants. Detoxification of contaminants is done by breaking the bonding within their molecular structure at elevated temperatures and certain amount of microwave conductors and absorbers need to be added to contaminated soil to enable to reach these high temperatures (Abramovitch et, al 1998, Krueger et al (2005: 206) complemented the results by finding out that maize planted in atmospheres that are iron-free lack rigidity, have retarded growth and have weak leaves. He also exposed barley seedlings to electromagnetic fields in a chamber that was ion-free and to chamber that was enriched with ions. After some time he realized that the plants in the ion-enriched chamber had grown more than those in ion-free chamber. His conclusion was that air-ions played a part in increased plant growth, but was not sure whether the increment in growth was as a result of air ions alone or both air ions and electromagnetic field. Conclusion Microwave treatment of soils promotes seed germination, speeds up seedling development and growth, promotes metabolic biosynthesis by increasing chloroplast density in leaves and improves hydraulic conductance by increase of minute vascular bundles. The natural earth’s electrical state is also vital to plant growth. Literature in this area of research indicates that electromagnetic radiation has a positive effect on some crops and a detrimental effect on others; thus it can be deduced that the impact of microwave treatment depends on three factors: exposure period; radiation frequency and the conditions of the environment in which the crop is planted. Analysis and results from earlier experiments reveal that lower power level with limited exposure time helps in growth of maize but very high levels of power with extended exposure time hampers growth. To substantiate the positive impact of microwave treatment in plants, intensive research to focus on the effect of electromagnetic radiation on the biological structure of cell organelles, genetic changes, yield quality and enzyme activities of different plants must be conducted. Bibliography Abramovitch, R., Huang, B., Davis, M., and Peters, L. (1998): Decomposition of PCBs and other polychlorinated aromatics in soil using microwave energy: Chemosphere Aladjadjiyan A. (2010): Study of the Influence of Magnetic Field on some Biological Characteristics of Zea Mais: Journal of Central European agriculture Anderson T. (1999): Design of Helmholtz Coil for susceptibility Testing Using Variational Calculus and Experimental Verification: Electromagnetic Compatibility IEEE Symposium, p601-604 Bachman, H. Hademenos G. and Underwood, S. (2001): Ozone and air ions accompanying biological applications of electric: Journal of Atmospheric and Terrestrial Physics 33(3): p497-508. Banik, S Ganguly, S. and Dan, D. (2006): Effect of microwave irradiated Methanosarcina barkeri DSM-804 on Biomethanation: Bioresources Technology, p 819–823. Barker, A. and Craker, L. (1991): Inhibition of weed seed germination by microwaves. Agronomy Journal, 83(2): 302-305 Blackman, H. (1994): Field experiments in electro culture: J. Agric. Sci. (Cambridge) 14: p240-267. Blackman, H. and Jorgensen, I. (1987): The overhead electric discharge and crop production: Journal of the Board of Agriculture 24: p45-49. Board of Agriculture and Fisheries: (1935): Reports 1-18 of the Electro-Culture Committee (Chairman Sir J. Snell). Microfilm copy available from Ministry of Agriculture, Food and Fisheries: Great Westminster House, Horseferry Road, London SW 1 P 2AE. Bown,R. (1997): Low energy irradiation of seed lots, Agricult. Eng. September, p666–669. Briggs, L. Campbell, B. Heald R. and Flint, L. (2006): Electroculture. U.S.D.A. Dept. Bull. p1379. Brodie, G. (2007): Microwave treatment accelerates solar timber drying. Transaction of the American Society of Agricultural and Biological Engineers, 50(2): 389-396 Casada M and Walton L: (1983) Moisture content as a function of temperature rise in Microwave Radiation: Transactions of the American Society of Agricultural Engineers, p 907 - 911 Chalmers, A. (2007): Atmospheric Electricity: Pergamon Press Ltd., Oxford. Davis, F., Wayland, J. and Merkle, M. (1973): Phytotoxicity of a UHF Electromagnetic Field, Nature, 241(5387): 291-292. Dimitris J. and Margaritis L. (2005): Theoretical Considerations for the Biological Effects of Electromagnetic Fields: University of Athenes, Department of Cell Biology and Biophysics Fischer, G. Tausz M. Kock, M.and Grill, D. (2004): Effects of Weak Magnetic Fields on growth Parameters of Young Cereals: Bioelectromagnetics, Vol25: p638-641. Hendrick, J. (1998): Experiments on the treatment of growing crops with overhead electric discharges. Scott: Journal of Agric. 1: p160-171. Jones R. (2001) Effect of Light on Germination of Forest Tree Seed: Proceedings of the International Seed Testing Association Jorgensen, I and Priestly, H. (2004): The Distribution of the Overhead Electrical Discharge Employed in Recent Agricultural Experiments: J. Agric. Sci. (Cambridge) 6: p337- 348 Kazuhiko, Y. Ono, T. Saito, D. and Saito, M. (1999): Effect of Static magnetic Field on Cell growth and Mitochondria: IEEE TENCON Kotaka, S. and Krueger, P. (2004): Studies on the air-ion-induced growth increase in higher plants: Advancing Frontiers P1. Sci. 20: p115-208. Krueger, P. Kotaka, S. and P. Andriese, C. (2005): The effect of abnormally low concentrations of air ion on the growth of Hordeum vulgare: Int. J. Biometeorol. 9(3): p201-209. Lemstrom, S. (2004): Electricity in agriculture and horticulture. The Electrician Printing and Publishing Co., London. Macelloni, G. Paloscia S. Pampaloni, P. and Ruisi, R. (1998): Microwave Emission Features of Crops with Vertical Stems: IEEE transactions on geoscience and remote sensing, Vol. 36, no. 1, Murr, E. (2004): Optical Microscopy Investigation of Plant Cell Destruction in an Electrostatic field. Proc. Pennsylvania Acad. Sci. 37: p109-121. Nelson O. (1987): Potential Agricultural Applications for RF and microwave Energy: Transactions of the American Society of Agricultural Engineers, p819-822. Newman, J. (1971): Electricity as Aplied to Agriculture: The Electrician, p 915 Okabe, T. Huang M and Okamura S (1973): A new Method for the measurement of Grain Moisture Content by use of Microwaves: Journal of Agricultural Engineering Research, p59-66. Priestley, J. (2010): Overhead electrical discharges and plant growth: J. Board. Agric. 17: p16-28. Racucuci, M. Creanga, D. and Amoraritei C (2007) Biochemical Changes Induced by Low Frequency Magnetic Exposure of Vegetal Organisms: Journ. Phys, p645-651 Ragha, L. Mishra, S. Ramachandran, V. and Bhatia, M. (2011): Effects of low-power microwave fields on seed germination and growth rate: Journal of Electromagnetic Analysis and Applications, Vol. 3, pp. p165-171 Schottenfield, B. (2009): Electric fields in plants: Annual Rev. P1. Physiol. 18: p409-418. Shibusawa, M. and Shibata, K. (1970): The Effect of Electric Discharges on the Rates of Growth of Plants: Biol. Abstract 4(10) p2257 Read More