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Why blue light affects vegetation growth.
Hey
Okay maybe if I explain how I did my project then you will know what sort of an answer i am looking for. I got three plastic cups filled it up with soil and planted 10 radish seedlings in each of them. On the first cup I covered it with blue plastic, on the second cup I covered it with red plastic and on the third cup I didnt cover it with anything because I wanted to test that on normal sunlight. I did not use any different coloured light bulbs.I set my project outside under the sun. I tested the radish seedlings out over a three week period in the end I discovered that the blue plastic covered cup the plant grew best in. My teacher wants to know why that is she wants to know the scientific idea behind my experiment... i told her, from my research that blue light helps vegetables grow fastest...then she asks why, i tell her that it has more of an effect on the plant than red light or norml sunlight, because red light is better for flowering plants. she still goes and asks me why... So really the question that I want to ask you is why did the blue covered cup help my plant grow at a faster rate. Thanks |
#2
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Why blue light affects vegetation growth.
In article .com, "misswizz" wrote:
Hey Okay maybe if I explain how I did my project then you will know what sort of an answer i am looking for. I got three plastic cups filled it up with soil and planted 10 radish seedlings in each of them. On the first cup I covered it with blue plastic, on the second cup I covered it with red plastic and on the third cup I didnt cover it with anything because I wanted to test that on normal sunlight. I did not use any different coloured light bulbs.I set my project outside under the sun. I tested the radish seedlings out over a three week period in the end I discovered that the blue plastic covered cup the plant grew best in. My teacher wants to know why that is she wants to know the scientific idea behind my experiment... i told her, from my research that blue light helps vegetables grow fastest...then she asks why, i tell her that it has more of an effect on the plant than red light or norml sunlight, because red light is better for flowering plants. she still goes and asks me why... So really the question that I want to ask you is why did the blue covered cup help my plant grow at a faster rate. More fertiliser? Cheers, Phred. -- LID |
#3
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Why blue light affects vegetation growth.
"misswizz" wrote in message
oups.com... Hey Okay maybe if I explain how I did my project then you will know what sort of an answer i am looking for. I got three plastic cups filled it up with soil and planted 10 radish seedlings in each of them. On the first cup I covered it with blue plastic, on the second cup I covered it with red plastic and on the third cup I didnt cover it with anything because I wanted to test that on normal sunlight. I did not use any different coloured light bulbs.I set my project outside under the sun. I tested the radish seedlings out over a three week period in the end I discovered that the blue plastic covered cup the plant grew best in. My teacher wants to know why that is she wants to know the scientific idea behind my experiment... i told her, from my research that blue light helps vegetables grow fastest...then she asks why, i tell her that it has more of an effect on the plant than red light or norml sunlight, because red light is better for flowering plants. she still goes and asks me why... So really the question that I want to ask you is why did the blue covered cup help my plant grow at a faster rate. We need more details of *how* you covered the seedlings with the blue plastic. Did you cover these seedlings so that there was a free flow of air (i.e.absolutely free flow) around them? Or did you cover the seedlings with the blue plastic in such a way that the flow of air was hindered? If you did the latter, you effectively placed these seedlings in a greenhouse, so that they grew in a hotter environment than did the seedlings that were exposed to direct sunlight without a plastic "greenhouse". Even if you accept this idea, you would still need to explain why the seedlings under the blue plastic grew better than the ones under the red plastic. You have received many excellent suggestions to answer this point. It is worth remarking that plant growth is not the only thing that depends on the colour of the light. Photographers (in the old days of black and white photography) used to work in darkrooms that were illuminated by a red light. This was because the emulsion on the photographic paper was sensitive to blue/green/yellow light, but not to red. Tanning of the skin, and skin cancer, are both caused by ultra-violet light, but not (to any significant extent) by red, green or blue light. From a physicist's point of view, light arrives as a shower of millions of "photons" - which are individual packets of light energy (much as an atom is a individual packet of a given chemical element, or an electron is an individual packet of electrical charge). The energy of each photon depends on the wavelength of the light. The shorter the wavelength, the higher the energy of each photon. Red light has a relatively long wavelength, and each individual photon has a relatively low energy. To a large extent, therefore, each photon of red light has insufficient energy to initiate a chemical reaction. Because the wavelength of blue light is approximately half that of red, each individual photon of blue light has twice the energy. This extra energy is often sufficient to initiate a chemical reaction, such as photosynthesis, but is relatively ineffective in tanning your skin or causing skin cancer. Ultra-violet light is even shorter wavelength than blue, has an even higher photon energy, and can cause the chemical reactions of tanning and skin cancer. The energy of far-ultra-violet light may be so high that plant leaves might experience more damage than beneficial photosynthesis if exposed to it. Our eyes may also be damaged by exposure to excessive ultra-violet light, again because of the high photon energy. Richard Chambers Leeds UK. |
#4
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Why blue light affects vegetation growth.
How was plant growth measured in the experiment and what were the plant
data for the three treatments? Although often used by students, height is often not the best measure of plant growth. Plants that grow tall may be thinner and gain less weight than shorter plants. A better measure of plant growth is shoot fresh weight or dry weight. Covering a plant with colored plastic will significantly reduce the amount of Photosynthetically Active Radiation (PAR) that a plant receives. The rate of photosynthesis and plant growth is often directly proportional to the amount of PAR the plant receives. PAR counts the number of photons between 400 and 700 nanometers in wavelength, which is visible light. In photosynthesis, the energy of a photon is not important; basically a red photon is just as good as a blue photon. Therefore, one would expect that a plant receiving full sunlight would grow better than one receiving only the red or blue wavelengths in sunlight. To fairly compare plant growth under different colors of light would require using a PAR meter so that all plants received the same amount of PAR. Unfortunately, PAR meters are expensive so are not usually available for student projects. I believe Dick Chambers has possibly the best explanation - that the blue plastic covering the cup provided a better environment for the plants than the uncovered plants that received full sunlight. The plastic covering could have increased the temperature or retained more water. The appropriate control treatment would have been a cup covered with clear plastic. Another possibility is that the results occurred just due to chance. There should always be replication of three or more pots per treatment in order to take into account the natural variability in plants and the possibility of a plant dying or growing poorly in a treatment for reasons unrelated to the experimental treatment. Questions about projects like yours come up frequently at madsci.org - http://madsci.org/circumnav/index.html The MadSci.org botany archives can be searched for light color. David R. Hershey |
#5
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Why blue light affects vegetation growth.
Thank you very much for your reply
I did indeed repeat my experiment overall 3 times. My results were still the same. |
#6
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Why blue light affects vegetation growth.
"misswizz" wrote in message ups.com... Hey shaniya here. Thank you vey much for your reply. I was wondering if you could explain to me the difference between the wavelengths of blue light and sunlight. Answer to this question would be highly appreciated. ----------------- I will try to do so, if you will explain to me what "Hey shaniya" means. Sunlight is a mixture of colours, from ultra-violet (which you cannot see, but which you can certainly detect and measure with the appropriate instruments), through violet, blue, green, yellow, orange, red, and then to infra-red. Infra-red is also invisible to the human eye, but (like ultra-violet) can be detected and measured using the appropriate instruments. The fact that white light is a mixture of all the main colours explains why you see the various colours of the rainbow when a beam of white light is passed through a prism. It is also the underlying reason why you see "all the colours of the rainbow" when you look at a rainbow. Indirectly, it also is part of the explanation of why the sky is blue, and the sunset red. Blue light is just one of the constituent colours of white light. The blue plastic that you have put over one of your pots of radish seedlings has the effect of blocking the red, yellow and much of the green light from the sun, while it is transparent to the blue light. That is why you can still see objects by looking through the plastic, but they all seem blue. Your radish seedlings will receive all the blue-light constuent of the sunlight, but the other colours will be blocked. Because the red and yellow light have been blocked by the blue plastic, the seedlings in this pot are, in fact, receiving less sunlight energy than the seedlings that you have exposed to direct sunlight. Does this matter? Red light has a wavelength of around 800nm, while blue light is around 400nm. The shorter the wavelength, the higher the energy of the individual photon. An individual photon of blue light has approximately twice the amout of energy that an individual photon of red light has. For some types of photosynthesis in some types of plant, the red photon simply does not have sufficient energy to initiate a chemical reaction, while the higher energy of a blue photon does produce photosynthesis. If this is the case with radishes (and I do not know whether it is), removing the red and yellow light by use of your blue plastic should (theoretically) have no effect on the growth of the seedlings. All that would matter in such a case is "how much blue light the plant receives". Richard Chambers Leeds UK. |
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