The effects of different pigments on photosynthetic activity in Plectranthus spp. [Scientific Research Paper]

alchemage (66)in #science • 7 years ago (edited)

Abstract

In this experiment we tested how different pigments affect the process of photosynthesis in Plectranthus spp. We accomplished this by breifly boiling a mature leaf from the specimen in alcohol to remove the pigments. We then placed the leaf in a solution of iodine to check for the presence of starch production in the leaf. Where there was photosynthesis occuring, starch would be present. Iodine stains blue in the presence of starch. The leaf showed significant blue stains along the edge of the leaf where the most green pigments were present and little to no blue staining in the center where the most purple pigments were present.

Source

Introduction

Photosynthesis is one of the most important, if not the most important, processes which occurs on our planet. Photosynthesis is the backbone to supporting life here on Earth. Sunlight and carbon dioxide (CO2) are converted into glucose, which are converted into starch for storage, and oxygen through the process of photosynthesis. This oxygen that is produced allows for life as we know it. Moreover, these sugars which contain carbon, alongside hydrogen and oxygen (commonly at a 1-2-1 ratio, respectively), are the main source of carbon within the human diet, be it directly from the plant or indirectly through consuming other herbivores/omnivores.

Plants capture CO2 through their stomata, coupling it with light energy within their leaves' substystems. According to Chris Turney (2009), vegetative species are directly responsible for channeling 120 billion tons of carbon dioxide per year, a distinguishably larger amount compared to the 8.5 billion tons released by the burning of fossil fuels each year. However, a large amount of that captured CO2 is released back to the atmosphere through respiration and decompisition (Turney 2009). As we increase our levels of CO2 production each year, it is important to know which plants are capturing the most CO2 in order to continue fixing carbon from the atmosphere effectively. Plants which capture large amounts of carbon may possibly be a strong point of focus as they might allow us to reduce the carbon footprint involved in producing a source of manmade carbon fixation.

The sunlight received by plants that is used to drive photosynthesis with CO2 carries the full spectrum of color. Species throughout the entire Plantae kingdom are known to display a variety of stunning and vibrant colors. A study conducted by Andrew A. Pascal and et al. (2005), shows that plants have developed antanae-like molecules which collect photons and deliver them to the reaction center where the synthesis of oxygen occurs. Each of these molecules is specially designed to capture or reflect specific wavelengths of light. A plant in the shade effectively carries out photosynthesis at a greater rate than plants that exist in full sunlight because a large portion of the energy absorbed in full sunlight is not required by the plant. This excess energy is absorbed as heat, thus plants have developed certain pigments to dissipate this excess heat and sheild themselves from being damaged (Pascal and et al., 2005).

The two most common light-absorbing pigments are chlorophyll a and chlorophyll b. According to analysis collected by B. Raychaudhuri and S. Bhattacharyya (2008), chlorophyll a displayed the highest absorption rates around 430 and 663 nm, blue and red respectively. Correspondingly, chlorophyll b displayed absorption rates around 470 and 650 nm ( Raychaudhuri and Bhattacharyya, 2008). The Plectranthus spp. used in this experiment contained both green and purple pigments, chlorophyll a & chlorophyll b, and anthocyanins. Our hypothesis was the specimen would stain the iodine blue where there are the highest concentrations of chlorophyll a & chlorophyll b present. If chlorophyll a & b drive photosynthesis, then there will be sugars present. Where there are high concentrations of anthocyanins there will be no photosynthetic activity.

Materials and Methods

The presence of photosynthetic activity was tested by using an alcohol boiling bath set up by placing a 400 mL beaker containing 200 mL of 80% ethyl-alcohol inside of an 1,000 mL beaker containing 300 mL of boiling water. One mature leaf was then removed from a Plectranthus spp. specimen after receiving several hours of strong light and then placed into the alcohol solution. When the pigments had been dissolved into the alcohol and the leaf was nearly white, forceps were used to remove the leaf. To test for the presence of photosynthetic activity the leaf was then placed into a solution of enough distilled water to cover the leaf and enough iodine to turn the water amber. After about five minutes the results were clear.

Results

We found that our results were positive. The areas which showed the highest chlorophyll a & b concentrations exhibited the presence of photosynthetic activity by staining the iodine blue indicating the presence of starch. The areas with the highest concentration of anthocyanins exhibited no indication of photosynthetic activity (Table 1).

Discussion

As we predicted, the highest presence of starch was exhibited in the regions of the Plectranthus spp. leaf which displayed the highest concentration of chlorophyll a & chlorophyll b. Photons from light energy and CO2 stimulate the chlorophyll molecules to initiate the photosynthetic process. A recent study published by Geun Ho Gim and et al. (2016) showed that with increasing light intensity (up to 150 micro mol/m(squared)/s) chlorophyll concentration increased which also increased the concentration of starch (Gim and et al., 2016). According to A. F. Solovchenko and O. B. Chivkunova, anthocyanins absorb 95% of the visible UV spectrum. This leads one to conclude that anthocyanins act in a way to dissipate excess heat energy from damaging the plant (Solovchenko and Chivkunova, 2011). One of the problems we faced was keeping the leaf from folding. Once it had folded it was nearly impossible to get it to come apart fully without damaging the specimen. Knowing that anthocyanins are antioxidants in the human body, further research could be conducted on the connection between its absortion rates and its antioxidant characteristics.

Literature Cited

Gim GH, Ryu J, Kim MJ, Kim PI, Kim SW. Effects of carbon source and light intensity on the growth and total lipid production of three microalgae under different culture conditions. Journal of Industrial Microbiology & Biotechnology. 2016;43(5):p605–616.

Pascal AA, Liu Z, Broess K, Oort BV, Amerongen HV, Wang C, Horton P, Robert B, Chang W, Ruban A. Molecular basis of photoprotection and control of photosynthetic light-harvesting. Nature. 2005;436(7047):p134–137.

Raychaudhuri B, (Bhaumik) SB. Molecular level all-optical logic with chlorophyll absorption spectrum and polarization sensitivity. Applied Physics B. 2008;91(3-4):p545–550.

Solovchenko AE, Chivkunova OB. Physiological role of anthocyanin accumulation in common hazel juvenile leaves. Russian Journal of Plant Physiology. 2011;58(4):p674–680.

Turney, Chris. Fixing Nitrogen – the natural way. The Chemical Engineer. 2009;813:p44-45

#steemstem #life #nature #writing