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yl- research paper - How Direction of the Light Source...

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How Direction of the Light Source Influences Direction of Plant Growth Taarika George I.D. # 09285 Due 12/22/04 Period F
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The problem to be investigated in this experiment is to see whether bean stems will grow downward if their only light sources come from below. The purpose of this investigation is to see whether plants are affected by the direction of light that they receive. This will show whether plants are just meant to grow upwards, or that the reason they do grow upwards is because their light source comes from above. If light sources come from below, then the plants will grow downwards. This is because previous studies have shown that plants grow toward their light source. The plants need the light in order to perform photosynthesis, so they need whatever light they can get. If the only light source they can get is coming from underneath, they will have to use it in order to live. In this experiment, the independent variable is the direction of the light. The direction of the light will influence how the beans will grow. So, the dependent variable is the direction of plant growth. The hypothesis in this experiment is: If light sources come from below, then the plants will grow downwards. This is because prior investigations have shown that plants grow toward the direction that their source of light is coming from. The plants need the light to carry out photosynthesis, so they need whatever light they can get. If the only light source they can get is coming from below, they will have to use it in order to live. The reason this hypothesis is like this is because of what previous experiments have shown. They have shown that plants grow toward their light source. This makes logical sense because plants need light to carry out photosynthesis. There are also many other factors that will prove that the plants will grow downwards. In this experiment, it will be seen that when the light comes from underneath, the plants will grow downwards, 2
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because that is where their light is coming from, and they need it to go through photosynthesis. In the hypothesis it was mentioned that previous studies had shown that plants grow towards their light source. Through research, it was found over and over again that plants do indeed respond to the direction of light. This is called phototropism. The definition of phototropism is the unequal growth of a plant part in response to a one sided source of light (Stone 204). Some plants have this response because of light- mediated breakdown of auxins, which are chemicals that enhance the lengthening of cells (Stone 204). Charles Darwin performed an experiment using corn coleoptiles. He let them germinate in the dark and then put them in a black box, with light coming from only one window on the side. The result was that all of them curved towards the light in
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This note was uploaded on 09/11/2011 for the course RECON 69 taught by Professor Bahls during the Spring '98 term at Northeastern.

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yl- research paper - How Direction of the Light Source...

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