Magnesium (Mg) is a metallic chemical element found in the soil, vital for both animal and plant life. A secondary nutrient, in terms of quantity, it is just as critical as any other element, and is the driving force behind photosynthesis1. Chlorophyll, the pigment that gives plants the distinct green colour and carries out photosynthesis, needs magnesium to catch the incoming solar energy from the Sun. A deficiency of magnesium in plants results in decreased plant growth, fruit production, and eventual death.2 An excess of magnesium also causes serious problems as it results in competition with other necessary elements such as potassium and calcium, culminating in plant death.3
The plant I have decided to use is the mung bean. The reasons to why I am using mung bean plants (Vigna Radiata) for this biological experiment are because they are easy to grow in a variety of environments, grow quickly, and are cheap. As magnesium is very water-soluble, I will be providing my soil with excess water, this will leach magnesium to the lower layers of the soil. The rationale behind this is to stimulate natural soil after a very heavy rainfall, something that is happening more commonly due to climate change.4 In this study, I will be using varying concentrations of Magnesium (Mg2+) to determine how the growth of V. Radiata is affected. Since a deficiency of magnesium results in lesser plant growth, I will use fertilizer to provide additional magnesium and other nutrients in an attempt to offset the lack of magnesium. Without sufficient amounts of this element, chlorophyll in plant leaves begin to degrade, resulting in the yellowing of leaves and decrease in plant growth, it is also critical for the activation of many enzymes such as Rubisco5.
Often, humans add nutrients to aid plant growth, in the form of fertilizers. For this investigation, fertilizer will be added to the group B plants in order to determine to what extent the effects of low magnesium concentrations can be negated by the addition of fertilizer. The magnesium will be added in the beginning of the experiment, to allow me to see how much the effect of magnesium deficiency is reduced over a period of time as opposed to plants without fertilizer. The initial flooding of water will cause magnesium to go to the lower layers of the soil. As roots grow longer, they are able to absorb nutrients with significantly greater ease. 6 Perhaps, this would negate some of the impact a lack of magnesium has on the growth rate because magnesium is a necessary element and the roots will attempt to attain satisfactory amounts. The purpose of this investigation is to see clearly the effect low magnesium concentrations have on the growth of mung beans (V. radiata) and whether fertilizer can make them better suited for soils with low magnesium concentrations.
1.2 Choice of Topic
My favourite units in Biology HL were topic four: ecology and topic five: evolution and biodiversity. In Biology HL, I learnt some of the major factors that affect germination and plant growth such as water, temperature, and sunlight. Also, I strongly believe that pollution and climate change currently are one of the biggest problems that humans are facing. As such, I decided I wanted to do an investigation that related to this topic. Gardening is also a personal hobby that I’ve been undertaking since the age of twelve. I find the “struggle” of plants, as they grow from a miniscule seed to large plants, very captivating. Due to these reasons, I intransigently chose to do something based on plants.
In many fast developing areas of the world today, governments give precedence to economic growth, instead of environmental friendliness. Climate change and pollution are quickly decreasing the available amount of arable land, then, overpopulation puts even greater stresses on the lesser amount of cultivable land available.7 A positive feedback loop begins in which countries are cutting down forests and green spaces to make space for agriculture due to the higher demand from population. An eight-year study done by China showed that 19.4% of its cultivable land showed contamination.8 Thus, soil contamination, too, is a very serious issue. Although the Environmental Protection Ministry of PRC named nickel, cadmium, and arsenic as top pollutants, other non-related studies have stressed the importance of magnesium to plants as well as the effects of an excess amount. 9 10 In the end, I decided to research how a magnesium deficiency affects plant growth.
1 Role of Magnesium in Plant Culture. (2017, September 12). Retrieved October 15, 2017, from https://www.pthorticulture.com/en/training-center/role-of-magnesium-in-plant-culture/
2 Patterson, S. (2016, November 27). Understanding The Role of Magnesium in Plants – How Do Plants Use Magnesium. Retrieved June, 2017, from https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/fixing-magnesium-deficiency.htm
3 Rempe, S. (2017, July 17). Too Much Magnesium for Plants | Hunker. Retrieved August, 2017, from https://www.hunker.com/13428066/too-much-magnesium-for-plants
4 Climate Change Indicators: Heavy Precipitation. (2017, January 12). Retrieved August, 2017, from https://www.epa.gov/climate-indicators/climate-change-indicators-heavy-precipitation
5 Magnesium: The Lamp of Life – Chlorophyll, DNA, DHEA and Cholesterol. (2016, December 10). Retrieved September, 2017, from http://drsircus.com/magnesium/magnesium-the-lamp-of-life/
6 (n.d.). Retrieved August, 2017, from http://facweb.furman.edu/~lthompson/bgy34/plantanatomy/plant_root.htm
7 Zhang, X., & Cai, X. (2011, March 18). Climate change impacts on global agricultural land availability. Retrieved September, 2017, from http://iopscience.iop.org/article/10.1088/1748-9326/6/1/014014/meta
8 (n.d.). Retrieved September, 2017, from http://www.mep.gov.cn/gkml/hbb/qt/201404/t20140417_270670.htm
9 Guo, W., Nazim, H., Liang, Z., & Yiang, D. (2016). Magnesium deficiency in plants: An urgent problem. The Crop Journal, 4(2), 83-91. doi:https://doi.org/10.1016/j.cj.2015.11.003
10 Selvaraj Venkatesan and Sankar Jayaganesh, 2010. Characterisation of Magnesium Toxicity, its Influence on Amino Acid Synthesis Pathway and Biochemical Parameters of Tea. Research Journal of Phytochemistry, 4: 67-77.