The light from the Sun and the presence of carbon dioxide is crucial in propelling the process of photosynthesis. It is these main factors that plants can grow and expand. However, the threat of climate change will dramatically alter the conditions in which flora can thrive in. Hence forth this experiment is to model and investigate the impacts of climate change on plants via a combination of light intensity and carbon dioxide presence.
Climate change is heavily linked to an increase of carbon dioxide in the atmosphere. Trend in atmospheric CO2 concentration has been on the rise and it is concluded that their elevated presence has led to faster photosynthetic rate and plant growth (Kaiser et al., 2014). Despite that, both C4 and C3 plants have a saturation point where CO2 can no longer contribute to their development (Ghannoum et al., 2000).
However, as CO2 rises, so does temperature. Plants can function at a high temperature but only to a certain extent. As it is projected that in 30-50 years, the average temperature will rise within a range of 2-3 °C (Intergovernmental Panel Climate Change (IPCC) (2007)), many plant species will begin to experience extreme dryness, thus overall decreasing the efficiency of photosynthesis.
One example was shown in maize growth, where its reproductive stage of development was exposed to a much higher temperature than its normal regime. The grain yield was largely reduced by around 80-90% (Jerry et al., 2015). Therefore, with heat waves or extreme temperature are predicted to become more intense, there will be a few days with temperature increases of over 5 °C above the expected temperatures. One of the possible effects of excessive heat has been studied to show a reduction in grain numbers in wheat (Triticum aestivum) and decreased duration of the grain-filling period (Barlow et al., 2015). Whereas during frost, it modified the form grains to cause sterility and consequently, damaging the plant itself.
Furthermore, light is a source of energy for photosynthesis; however, it can also become a stress factor for the plants. Under extreme light, it can suppress photosynthesis, known as photoinhibition. When plants are stressed, that is under intense light, the energy supply (ATP) and NADPH exceeds the demand for the metabolic processes (Miyake et al. 2009). In those conditions, the plants have their own mechanisms of mitigating the damage. One the methods is the dissipation of the excess energy in the form of heat to reduce the damage.
To further the understanding of the impacts of climate change on plants, this experiment stimulates rocket, Eruca sativa, under low/high light and ambient/elevated CO2 conditions. Its leaf area was then used to measure the growth and the rate of photosynthesis, to see how flora would react in a modelled setting. If the concentration of CO2 were elevated along with the amount of light, the photosynthesis rate and plant growth of E. sativa will increase.
The experiment supported the hypothesis provided. It showed that having access to more light and CO2 does greatly influence a plant’s growth, as indicated by the leaf area average. The two figures had a huge gap in terms of their p value. Therefore, there is a statistically significant difference, indicating that the difference occurred is not due to chance, but rather due to the access of light and carbon dioxide for the plants.
These results were as expected, where having readily access to resources allowed further growth. This is also supported in an experiment that assessed the growth responses of C4 and C3 plants, against elevated CO¬2 levels (Ghannoum et al., 2000). The paper aims to explore the mechanics of how C4 plants accumulate great biomass at higher CO2 atmospheric levels. Majority of plants are categorised as C3, all having a feature of non-compatibility under warmer temperatures as compared to C4 plants. Indicating that their photosynthesis process is dependent on the carbon dioxide that is available as opposed to C4 plants (Uprety, Sen and Dwivedi, 2010), where they focused on the grain quality of crops in changing CO2 conditions. It showed that C4 plants under elevated carbon dioxide conditions, did not have much of a difference in growth and yield.
At elevated CO2 conditions of around 475-600ppm, the average leaf photosynthetic rate increased by 40% (Uprety, Sen and Dwivedi, 2010). With constant exposure to CO2, plants had low stomatal conductance, decreasing the plant’s overall water usage, estimated to be 5-20%. Despite the less need of water, this showed that climate change had a profound effect in increasing both the soil moisture and runoff. Elevated CO2 also lead to the carbohydrates per leaf area to increase by an average of 30-40% (Ainsworth and Long, 2004). The studies all supported the results that higher CO2 concentrations allowed for faster plant growth, but they all presented that is not the only factor in plant development and will become a saturation point when it is too high. A limitless supply of carbon dioxide does not equate to the high presence of other resources that is needed, like minerals and nitrogen. Therefore, as plants respond with increased photosynthetic rate in elevated CO2 conditions, they are still limited by the nutrients available in the soil.
Another factor that this experiment concentrated on was how light played a role in plant growth. The many characteristics in light such as intensity, duration and direction can influence the plant’s development. This experiment only used intensity as a measure, but light spectra also plays a large role (Bayat et al., 2018). Plants under excess light will choose to decrease the amount that it needs to absorb for photosynthesis, therefore indicating that there is a saturation point. Another method of mitigation under high light intensity is that the plants will release the excess energy in the form of heat (Miyake et al. 2009). Therefore, high light helps plant growth only up to a certain point, under lighting of 250 μmol m−2 s−1, carbohydrate production decreased and there was a build of H2O2, which stalled the photosynthetic process (Bayat et al., 2018).
This experiment performed can be further improved by adding a control. This would assist in whether the experiment performed is valid, that the changes are in plant growth did occur. A control group enables each variable to be studied one at a time, to confirm if the supposed variable truly affects the subject. It is also to avoid bias from the researchers themselves and previously held beliefs (Pithon, 2013).
Also plant growth is affected by other factors like temperature and soil type, but since these factors were not the focus of this experiment, it is not conclusive whether they played an important role. As nitrogen is a major component of chlorophyll and amino acids, it is essential that plants require 3-4% in their soil (Gojon, 2017). Without it, plants wither and die as proteins act as the building blocks in their cells. It is known that plant size will increase with higher CO2 concentrations, therefore, the demand for nitrogen rises as well.
Furthermore, the study should be replicated with different types of plants, to see if the result obtained here are consistent across different species. C4 and C¬3 plants all react differently to the changing environmental conditions. Light intensity affects both types equally, but C3 plants benefits more from higher CO2 levels (Uprety, Sen and Dwivedi, 2010).
As a result, this research has further supported the understanding in maximising plant growth as the Earth undergoes a drastic change. The Earth is now experiencing an increase in carbon dioxide and this experiment will help explain how it will affect plant growth worldwide.
It is predicted that the severity of climate change will only aggravate further in the coming years. Plants are more sensitive to biological damage than any other organisms. Hence the main goal is to effectively reduce the greenhouse gases, specifically carbon dioxide. As a result, the process of photosynthesis in plants is paramount in curbing the presence of carbon dioxide.
Overall, the aim of this experiment was to investigate the effects of climate change on plants. This was achieved by using Eruca sativa, and it was subjected to a combination of elevated/ambient CO2 along with high/low light. Although this study needs to be further replicated and requires improvements, it has achieved its aim in modelling how the plants responded to climate change-like conditions. Despite that, this topic requires more in-depth research as factors like nitrogen and soil type has not been the focused on.
- Kaiser, E., Morales, A., Harbinson, J., Kromdijk, J., Heuvelink, E. and Marcelis, L. (2014). Dynamic photosynthesis in different environmental conditions. Journal of Experimental Botany, 66(9), pp.2415-2426.
- Ghannoum, O., Caemmerer, S., Ziska, L. and Conroy, J. (2000). The growth response of C 4 plants to rising atmospheric CO 2 partial pressure: a reassessment. Plant, Cell & Environment, 23(9), pp.931-942.
- Hatfield, J. and Prueger, J. (2015). Temperature extremes: Effect on plant growth and development. Weather and Climate Extremes, 10, pp.4-10.
- Tkemaladze, G. and Makhashvili, K. (2016). Climate changes and photosynthesis. Annals of Agrarian Science, 14(2), pp.119-126.
- Barlow, K., Christy, B., O’Leary, G., Riffkin, P. and Nuttall, J. (2015). Simulating the impact of extreme heat and frost events on wheat crop production: A review. Field Crops Research, 171, pp.109-119.
- Miyake, C., Amako, K., Shiraishi, N. and Sugimoto, T. (2009). Acclimation of Tobacco Leaves to High Light Intensity Drives the Plastoquinone Oxidation System—Relationship Among the Fraction of Open PSII Centers, Non-Photochemical Quenching of Chl Fluorescence and the Maximum Quantum Yield of PSII in the Dark. Plant and Cell Physiology, 50(4), pp.730-743.
- Uprety, D., Sen, S. and Dwivedi, N. (2010). Rising atmospheric carbon dioxide on grain quality in crop plants. Physiology and Molecular Biology of Plants, 16(3), pp.215-227.
- Ainsworth, E. and Long, S. (2004). What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytologist, 165(2), pp.351-372.
- Pithon, M. (2013). Importance of the control group in scientific research. Dental Press Journal of Orthodontics, 18(6), pp.13-14.
- Gojon, A. (2017). Nitrogen nutrition in plants: rapid progress and new challenges. Journal of Experimental Botany, 68(10), pp.2457-2462.