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light on plant growth

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An Investigation into the effect of Different Wavelengths Of Light on the Growth of Plants Pilot study data: The pilot study was designed to test which growth medium would be best for the cress, as well as the affect of different wavelengths of light on the plants growths. Method: All three of the containers had different colour films applied to them blue, green and red. The sides were covered in black sugar paper to prevent light other than the filtered light from passing through the cress. The blue film container had cotton wool as the growth medium. The red container had Perlite as its medium and the green container had filter paper as their media. The containers were all placed in the same location and had enough water throughout the experiment. The plants were measured using a ruler. Ten seeds were planted per container. The cress plants were measured daily and watered as necessary. The accuracy and precision of this experiment was maintained by using a millimetre-graduated ruler, as it was appropriate to measure cress in millimetres. The reliability of this study was ensured, by using replicates in the form of ten seeds per container rather than just the one seed per container. ...read more.


Experimental Hypothesis: The different wavelengths of light the plants receive will affect the plants photosynthetic rate and so indirectly affect the plants final height. I also hypothesise that the plants under red and blue light will grow to greater average heights. Results: Blue Film Day: (stem length in mm) Plant Number: 1 2 3 4 5 6 7 1 4 8 17 25 45 47 50 2 3 5 12 26 33 36 38 3 6 8 23 27 31 35 39 4 5 9 17 23 27 32 42 5 3 6 15 22 29 37 43 6 4 9 19 26 38 45 44 7 2 10 21 25 27 34 46 8 4 7 15 25 39 46 51 9 2 5 17 28 32 38 52 10 5 9 16 35 43 48 53 Red Film Day: (stem length in mm) Plant Number: 1 2 3 4 5 6 7 1 19 23 31 50 55 57 62 2 17 20 28 44 51 55 59 3 2 5 8 12 15 17 19 4 5 8 21 30 34 38 43 5 2 6 15 41 45 47 54 6 4 9 13 16 21 23 25 7 5 11 24 36 47 49 56 ...read more.


Averages (final heights): Mean: Red - 46.6mm Blue - 45.8mm Green - 40.2mm Median: Red film - 53.5mm Blue - 45mm Green - 43.5mm These average final heights also lend support to my hypothesis. The Blue light clearly benefitted the plant and so it grew to a greater final height due to an increased level of photosynthesis. The red film also experienced the same factors and came out with the second greatest final height. Red light ideally should have procured the greatest average as it is absorbed in slightly higher quanta. The chlorophyll absorption graph shows that chlorophyll a absorbs blue light at wavelength ranges 400-450nm and red light at 645-670nm. Using these ranges it may be possible that the light passing through the blue film was slightly out of the range of the absorption spectrum, this may have lead to the slightly decreased average of the blue film cress compared to the red film cress. The medians calculated show that the cress that grew under red light had the majority greater heights. This is essentially showing that the red light influenced the cress growth more than the green or blue light. The blue light also influenced the plants growth positively but not to as greater extent as the red light. ...read more.

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