To what extent does solar radiation of a high UV index passed through different coloured sheets impact the Trigonella foenum-graecum (fenugreek) plant growth(cms) during a span of 3 weeks

In the atmosphere, the solar radiation emitted from the sun can be categorised into three types - ultraviolet, visible and infrared light. The earth receives most of its radiation from UV radiation and visible light. On the other hand UV - C does not enter the atmosphere is reflected mostly by the ozone layer (Center for Devices and Radiological Health.). The visible light that reaches the earth is about 42.3%, infrared rays are about 49.4% and the ultraviolet radiation amount to over 8% (“Solar Radiation & Photosynthetically Active Radiation.”).

 

The UV radiation intensity is measured using a linear scale called the UV index. Higher the value of the index, the greater the potential damage to both human health and the environment. The varying values of the UV index is caused majorly by heavy cloud cover due to excessive pollutants in the atmosphere. It is used an indicator to create awareness amongst people to protect themselves from these intense UV radiation.

“Radiation: The Ultraviolet (UV) Index.” World Health Organization, World Health Organization, https://www.who.int/news-room/questions-and-answers/item/radiation-the-ultraviolet-(uv )-index 15.12.2022.

 

Moreover, the increase in the UV radiation from the sun/prolonged exposure which reaches the earth are mainly aggravated by human activities contributing to the depletion of the UV protective barrier - ozone layer. Chemicals like CFC’s, halons, VOCs released through human activities play a major role in contributing to ozone depletion. Furthermore, another human activity such as deforestation can reduce the green cover, thus exposing the bare surface towards intense UV radiation.An increased rate of deforestation aggravates the impacts of prolonged exposure of the UV rays on both humans and the environment. Prolonged exposure to these rays affect many plant species' productivity and have a negative effect on the growth of the plant leading to lower biomass and moreover also decreasing the moisture in the soil . Longer exposure of plants to these ultraviolet rays can reduce seed germination (Franklin). Moreover, due to these prolonged emission of rays, it changes the composition of food and decreases the nutrient content of the plant, impacting the economy as there is a decrease in food quality and quantity. For example, when plants are exposed to harmful ultraviolet radiation discolours plants and alters plants growth processes. Contrasting to that, when humans are subjected to harmful ultraviolet radiation, it can “induce free radicals in the dermis and diminish the skin's antioxidant capacity. (LBL A-Z). Increased ultraviolet radiation is a crucial issue to study because of the escalating consequences on the ecological balance of the environment and human health. This experiment was conducted during the November month in Hyderabad, India. The UV forecast during this time was very high and the average daily maximum UV index is 9 (Weather Atlas), indicating that the plant growth in this region is highly affected by the radiation which results in the damage to plants DNA, affecting the photosynthesis processes, hence negatively impacting the crop yield. In order to provide a solution to this environmental issue, the idea of shade nets have been researched and implemented in the agroindustry. Studies show that plants respond differently to various types of lights and their quality trigger different plant functions (Factors Hindering Crop Biomass Production: Possible Tools to Overcome ). For example, research shows that blue light helps in leaf growth, red and blue light combined helps the plants to flower (“Can Colored Lights Affect How Plants Grow?”). However, different colour filters helps plants to protect themselves by allowing absorption, reflection and scattering the colour they receive from visible light. In a world of growing population there is a growing need for crop yield and increased food production, thus it is essential for us to understand how each colour of light affects the plant growth/germination. For this investigation, the research will be based on the manipulation of different colour sheet ( as a model) and its effects on fenugreek plants.

I predict that the Fenugreek plant will flourish and grow in the red ultraviolet light while reflecting the green, blue and yellow colour light. This is because the pigment chlorophyll a reflects colours like green, blue and yellow while partially absorbing colours like red and orange through the process of photosynthesis (Koening).

Fenugreek (Trigonella foenum-graecum) was chosen as the type of plant for this experiment because of its quick growth rate and since the herb is a “shallow-rooted plant”, it doesn't require large amounts of space to grow it in. Moreover, Fenugreek is a staple leafy vegetable widely used for consumption and cooking purposes, hence has a huge value in various societies in Telangana. The naturally occurring white light is the best for photosynthesis but because of the prolonged ultraviolet radiation, plants are unable to properly grow in this light. In order to figure out the best plant growth, the white light would be manipulated in such a way that four different plants would be under four different colours. This will help in deciding which colour will be the best for plant growth/germination. This manipulation of colours will be done by wrapping boxes in coloured cellophane, hence making way for the plant to be exposed to one colour only for photosynthesis. Cellophane has been used as a model that simulates shade nets in this experiment because its cost-efficient and easy to utilise for the experiment.

Independent: 5 different coloured cellophane on the boxes - The range of wavelengths for each colour is as follows: Blue: 450-495 nm; Green: 495-570 nm; Yellow: 570-590 nm; Red: 620-750 nm; Visible Light - 400 - 700 nm Dependent: The growth of the Fenugreek plant in cms Controlled: Controlling the area of growth - loamy soil, type of plant used, Time taken across all trials, size of the container, amount of water used for watering

• 5 closed plastic boxes - 15 *12 inch
• 50 Fenugreek seeds
• Coloured cellophane - green, red, blue, yellow - 4 sheets
• Ruler - 15cm
• 5 Pots - 6 *6 inch
• Loamy Soil - 10 kg total
• Five 50ml glass measuring cups
• 1750 ml Tap water for watering

Set up

1. Half-fill the 5 pots with loamy soil
2. Then, plant 10 fenugreek seeds in each of the pot
3. Add a small layer of loamy soil to the cover the seeds visible outside
4. Pour 50mL of the distilled water into the clean, dry measuring cups
5. Water the 5 pots with 50mL of distilled water each
6. Take the 5 transparent boxes and the 4 coloured filament cellophane
7. Cut, cover and past each transparent box with the coloured cellophane and leave one of the boxes transparent
8. Take both the pots with the seeds and the boxes outside into a place with sufficient sunlight
9. Place each of the coloured cellophane wrapped transparent boxes on each one of the pots
10. For a span of 3 weeks , keep watering the plants with 50mL of distilled water
11. During the night, the transparent boxes will be opened, so that the plants do not get overheated in the closed boxes (based on the learnings from the previous pilot project)
12. Collect the quantitative and or qualitative data continuously for three weeks and calculate the average growth, analyse the error bars and standard deviations

No major risks were involved in this experiment. However, during the process of planting seeds, gloves were worn, so that any bacteria in the soil does not infect the skin and nail beds. Moreover, hands were also thoroughly washed with soap and water after the experiment.

There were no toxic chemicals involved in this experimentation. Nevertheless, in order to make sure that all the resources that have been used for this experiment do not go to waste, the loamy soil was disposed of in a designated place like the compost in the organic garden. Furthermore, the healthy plants were given to the organic farming at the academy, this ensures that these plants are treated rightfully.

• Initially the plants germinated well but with differing time periods for different trials pots and coloured filters
• As they reached the third week, they started drying up quickly as the the solar radiation became very intense, this has led me to conclude the experiment by the end of the third week

Formula for average

 

Average = (Sum of all observations) ÷ number of observations (n)

 

= (b₁+ b₂+ b₃+ b₄+ b₅) ÷ n 

 

Sample calculation for average -

 

From transparent

 

(7.8 + 6.9 + 7.2 + 7.5 + 7.8 + 6.6 + 7.2 + 7.8 + 6.9) ÷ 10 = 72.9 ÷ 1 = 7.29

This acts as a representation of the compatibility of the fenugreek plants considering the changing environmental and growing conditions. As the graph moves from the left to right, this depicts the increase in reflectivity of chlorophyll a (as mentioned in hypothesis). The downward sloping curve explains that as the reflectivity increases, the average growth rate of the fenugreek plant decreases. The transparent box has the highest average growth of 7.29cm while the yellow coloured filter covered box has the lowest average growth of 0cm, meaning that the plant flourishes well in visible light and does not flourish at all in yellow light. The other colours like red has an average growth of 6.09cm, green has a comparatively less average growth of 4.26cm and blue has an average growth rate less than green of 1.09cm. Moreover, the average growth also aids in estimating the plants biomass or yield. Thus, this estimated yield can be useful for food production and other purposes.

Error bar here is used to find out the uncertainty and the variability of the average fenugreek plant growth data. The length of the error bars here for all the values is similar for both the horizontal and vertical, upper and lower errors. This means that there is low uncertainty in the plant and the average growth data points are concise and certain and hence, making that data reliable to some extent.

The hypothesis that was suggested is partially supported by the data collected. The wavelength of red light consists of 620 - 750 nm and the experiment shows the average growth of the plant to be better than the other coloured lights. However, the blue which is supposed to be giving efficient results depicts a very low average growth rate and after a few days of germination, the plants died. This could be due to a procedural or methodological problem while conducting the experiment. Based on the experiment conducted, it has been found out that cellophane does not have the ability to filter out the UV light and allows only visible light. Moreover, the material of the cellophane is not appropriate to be used as a shade net compared to the commercial shade nets in agroindustry.

The effectiveness of coloured shades are predominantly determined by the type of the material being used. This means that with the use of better scientific coloured filters, the results of the experiment would have been more accurate. However, according to the sources, different colours are used by plant growers to manipulate the plants growth rate(Yılmaz). Through this experiment the ideal colour required is the visible/transparent light. This means that no colour should be found in excess for a stable and healthy plant growth, which in the data collected shows that average plant growth is highest for the transparent filter. Furthermore, the long term exposure to the a high index UV rays is detrimental to the health of plants and humans, impacting both health and food production systems.

The experiment was conducted in an optimum location with direct sunlight and the health of the plant was maintained by continuous checkups and regular watering. The range of colours chosen allows the visible light to be manipulated efficiently. Furthermore, there were air spaces provided for the boxes, so that the plants do not get overheated in them for long periods of time. The experiment is very convenient, cost-effective and can be implemented multiple times to derive accurate results.

For the experiment, the cellophane filters could have been replaced with actual UV coloured shades for more reliable data. The seeds should have been allowed to germinate into sprouts before being subjected to the experiment, this will help in ruling out any ungerminated seeds. The temperatures during the day time cross over 30°C. This temperature is not ideal to grow plants, especially in a closed box, leading to overheating. Thus, this overheating might have impacted the overall plant growth results, particularly in the blue and yellow coloured shades. More trials for this experiment, for example 5 pots for each colour (5*5), could have given made way for research to investigate the r value.

An area that can be investigated further is looking at the plant responses to different coloured shade nets with a wide range of shade percentages like 30%, 40%, 50%, etc.

One solution to solve this environmental issue of the effect of prolonged exposure to high UV index rays is to use shade covers or nets with recommended Shade % transparency for the fenugreek or similar leafy vegetable plants (“10 Simple and Effective Tips to Protect Your Plants in Summer.”). These shades help in cooling the plants and reduce the exposure to harmful radiation for the plant. This also decreases the amount of water evaporating from the plant, keeping them healthy and moist with good water retention capacity . Using this alternative could have resulted in an accelerated plant growth. Moreover, since plant shade is not uniform, its management is difficult and these shades can also restrict certain farming equipment (“Shading and Agroforestry.”). In addition, the shade nets retain moisture and lead to fungal growth. Decreased air circulation may increase the chances of pest and disease attack. However, if the aforementioned disadvantages are worked upon, the suggested solution can be a viable and reliable one to solve the environmental issue.

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