1. Research questionHow does different light affect photosynthesis i.e. plant growth?Photosynthesis is the proccess in which plants take in sunlight, water, CO2 and nutrients and create O2 and food. Via this proccess plants grow. The light spectrum is divided into three main colors, blue, green and red. Plants absorb blue and red, but they reflect green and that is why they are green. Through this experiment, the effect of every individual part of light will be explored.Three individuals of three different types of plants, spinach, radish and lettuce, will be grown over a 30 day period under 5 different lights; red, orange, green, blue and purple, in closed off compartments. Their growth will be measured after the 30 days via ruler. It is expected for the individuals under green light to grow the least and under red and blue light the most.2. VariablesIndependent: color of lightDependent: growth of plantsControlled: amount of O2, water provided for growth, temperature3. Control of variablesThe independent varaible will stay constant in each compartment through the time period of 30 days. The light will not be changed or turned off at any instance.The amount of oxygen cannot be strictly controlled in the conditions I am working in, but without changing the plants position or temperature, a constant will be provided. The amount of water will be constant as well, a 200 ml glass of water every three days.4. Materials

15 spinach seeds 15 radish seeds 15 lettuce seeds 45 medium sized plant bowls Package of soil 5 darkened compartments Ruler (0.05cm) Glass flask of 200 ml (0.1ml) Lightbulbs capable of emitting just red, orange, green, blue or purple light

5. MethodPrepare the plants by placing soil in the plant bowls half way, putting a seed and filling them up all the way. Place 3 bowls of each plant per one compartment, in total 5 darkened compartments with 9 plants per compartment under a certain light. Give the plants 200ml of water every third day and after a month, 30 days, measure each plants height with a ruler by placing the ruler to a 90 degree angle with the bowl and mark the highest leaf on the plant.Whole bowl of soil soilseedPreparation of bowl Top view of darkened compartment Row of lettuceRSRLLSLRSRow of spinachRow of radish

lightbulbbowlsSide view of darkened compartment

yMeasuring height of plant rulerTallest leaf90 degrees

yy

6. Raw dataTable 1. Lengths of spinach over respective colorsSPINACH LENGTH (cm)PLANT 1PLANT 2PLANT 3

RED16.316.516.622.221.922.318.418.518.7

ORANGE12.412.312.717.317.217.416.516.416.8

GREEN3.43.63.74.24.54.62.82.62.5

BLUE17.117.417.622.922.922.71818.518.3

VIOLET16.216.616.320.520.820.715.315.415.9

Table 2. Lengths of radish over respective colorsRADISH LENGTH (cm)PLANT 1PLANT 2PLANT 3

RED11.411.311.616.716.916.512.712.412.8

ORANGE7.47.87.311.211.511.66.46.36.1

GREEN1.41.71.62.62.92.51.51.11.2

BLUE16.116.216.517.417.317.716.816.416.5

VIOLET11.711.211.812.812.512.97.47.27.8

Table 3. Lengths of lettuce over respective colorsLETTUCE LENGTH (cm)PLANT 1PLANT 2PLANT 3

RED8.68.28.713.813.413.612.212.512.3

ORANGE5.65.35.410.510.310.75.85.35.4

GREEN3.13.53.64.84.24.62.93.12.7

BLUE11.410.911.215.615.615.510.610.510.4

VIOLET6.977.312.812.312.57.47.27.8

7. UncertainityThe uncertainty of the instrument with which I was dealing, a ruler, is 0.05 cm. 8. Proccessed dataThe average is calculated by adding up the three measurings and then dividing them by three.

Table 4. Average lengths of plants of respective colors for spinachAVERAGE SPINACH LENGTH (cm0.05cm)PLANT 1PLANT 2PLANT 3

RED16.4722.1318.53

ORANGE12.4717.3016.57

GREEN3.574.432.63

BLUE17.3722.8318.27

VIOLET16.3720.6715.53

Table 5. Average lengths of plants of respective colors for radishAVERAGE RADISH LENGTH (cm0.05cm)PLANT 1PLANT 2PLANT 3

RED11.4316.7012.63

ORANGE7.5011.436.27

GREEN1.572.671.27

BLUE16.2717.4716.57

VIOLET11.5712.737.47

Table 6. Average lengths of plants of respective colors for lettuceAVERAGE LETTUCE LENGTH (cm0.05cm)PLANT 1PLANT 2PLANT 3

RED8.5013.6012.33

ORANGE5.4310.505.50

GREEN3.404.532.90

BLUE11.1715.5710.50

VIOLET7.0712.537.47

Graph 1. Average length of spinach, radish and lettuce under five different parts of light

The x-axis contains the independent variable, the various colors, the y-axis the dependent variable, the length of the plants expressed in cm. The columns are the average height of each individual plant, 3 plants per a species. The blue columns are the spinach individuals, green radish individuals and orange lettuce individuals. As predicted, the shortest individuals were grown in the green light, over all plants averaging about 3 cm. The tallest were grown in blue light, over all plants averaging about 16 cm. Second comes red light with an average of 14 cm, violet with 12 cm and second to last orange with 10 cm. But the difference between height even between green and orange light is an average of 7 cm, and it just increases by color. From this evidence I can answer my research question (How does different light affect photosynthesis i.e. plant growth?) by saying that different colors in the light spectrum drastically affect the growth of plants, and that plants do absorb most of the spectrum with the exception of green with is mostly reflected off into our eyes. 7. ConclusionThe prediciton made at the beginning that the smallest plants will be grown in the green light and the tallest ones in red and blue has been suported by the evidence. As an average growth of plants in green light being 3 cm and from blue and red 16 cm an 14 cm respectively. One can futher conclude that the speed of photosynthesis is greater in all non-green light since green is the light that is being reflected and so not used in photosynthesis. An investigation made by NASA named Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps in which they compared biomass production, physiological characterizations light treatments influence morphology, water use, chlorophyll content, and the production of ATP within plant tissues by growing radishes and lettuce under a) red and blue LEDs and b) white flourescent lamps containing portions of green light, they saw that the plants were generally more productive under the white flourescent lamps because even though it contained green light, there were more colors (other than just red and blue) that contributed to the growth of the plants.[footnoteRef:1] [1: Mickens, Matthew A. Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps. Unknown, 2012. A Final Report Submitted in Fulfillment of the Requirements for the JPFP, Center-Based Research Experience (CBRE).]

8. EvaluationEvaluating errorsAn error could occur if the darkened compartments were not darkened completely and white light either directly from the Sun or inside light could hace affected the growth of plants, but considering that the experiment was done in a high school and not a specialized lab, that margin of error is acceptable. ImprovementsImprovments on the procedure itself could be to increase the number of individual plants per species and so to get better, precise data from which a more accurate conclusion could be drawn. The very location of the experiment could be more suitable, a complete dark room and/or better light bulbs or even LEDs for the light distribution. The pattern of distribution of plants under the light might have affected the data in less exposure and naturally less growth, so to improve the experiment, perhaps more light sources or simply a pattern in which all plants get equal light.9. ReferencesMickens, Matthew A. Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps. Unknown, 2012. A Final Report Submitted in Fulfillment of the Requirements for the JPFP, Center-Based Research Experience (CBRE).BBC - GCSE Bitesize: Photosynthesis, BBC, 2014, (2.1.2015.)Light and Plant Growth, Virtual Labs, unknown, (2.1.2015.)

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