How Does Phototropism Affect Pea Plants
For my science experiment I will be testing if phototropism affects pea plants. The purpose of this is to see how much the growth of the plant is affected by sunlight. Many years ago the scientist Charles Darwin discovered what today we called phototropism. I intend to create my own small experiment except this time I will be using artificial light instead of natural light (the sun).
The definition of tropism is "a growth movement whose direction is determined by the direction from which the stimulus strikes the plant" and "photo" means relating to light. There for, Phototropism is when a plant grows towards a light source. This is caused by a hormone. A hormone is any of various similar substances found in plants and insects that regulate development. The hormone that causes the plant to grow towards the light is called auxin. Auxin makes the cells divide and the plant to grow. The plant pumps more auxin to the side with the most shade causing the plant to be larger on one side, making the plant bend in the other direction.
The first scientist to ever experiment with phototropism was Charles Darwin. He was born in 1809 and died 1882. In his lifetime he wrote the famous book. On the Origin of Species. In 1880 Charles Darwin and his son Francis Darwin discovered that phototropism would not occur unless most of the plant was shaded. When they …show more content…
shaded the top of the plant phototropism did not occur so the plant stood up straight. However, when they put black sand up to the plants tip the plant would grow towards the light. The Darwins concluded that somehow the tip was causing more growth for the shaded area than the area with light.
Another scientist by the name Boysen Jensen held a phototropism experiment in 1913. Jensen cut the tip off of the tip then covered the tip with gelatin and replaced it. When he did this phototropism occurred. When he used a substance called impervious mica between the tip and the stump, phototropism was prevented. From this he concluded that the shaded area grows faster then the area with sunlight,
Though phototropism was occurring no one at that time knew it occurred because the hormone auxin. The scientist F.W. Went did an experiment that proved some chemical substance caused phototropism. He cut the tips of an Avena sativa and placed them on agar block, a gelatinous material derived from certain marine algae. After several hours he took the agar block and placed it on top of the plant. Growth took place because the auxin was stored in the block then given off to the plant, there for taking the job of the plant tip. All though F.W. Went discovered Auxin it was not known to the world yet as auxin.
The next experiment proved that unequal amounts of auxin causes bending in phototropism.
It was based off Went's experiment but the agar block was placed on one side of the plant and not in the middle. This caused the plant to grow curved. This is because the auxin went all to one side causing it to grow. One side growing faster then another causes the plant to bend. Gravity can cause an unequal amount of auxin. When a tip of a coleoptile is put on an agar block evenly both side of the block will get equal amounts of auxin but if you were to tip the 90 degrees one side of the agar block would receive more auxin then
another.
The ideal plant for an experiment involving phototropism would be a plant with a coleoptile like grass. Any flowering plant or a plant that grows something other then a stem on either side may ruin the results from the experiment.
I modeled my experiment after past experiments but changed some factors to help my results. Since I will not be growing the plants in the spring or summer, I will not use the sun as a source of light for the plants. Also the plants will not be grown outside but inside with a controlled temperature.
When I conduct my experiment I will be using artificial light from a flashlight to simulate the sun. The plant will have light only hitting half of it, which will cause the auxin to be spread more to one side than another. I will do this with five plants. For another five plants I will have even amount of sunlight hitting all parts of the plant causing an equal amount of auxin. For best result I'll keep the light on at all times for all the plants. Twice a day at the same time I will record the plants growth and the angle in which it grows in. I will do this until a week before the due date. Then I will average my data and organize it. After that I will graph it using a line graph. The graph should show the plants growth and tilt over time and how the two groups vary.
Phototropism is a very interesting topic that I think has not been explored enough. Many questions still need to be answered. If it wasn't for Charles Darwin and his son people today would have not noticed there was a thing, such as phototropism. All though phototropism seems to be a minor role in plant growth it plays a major roll. If a plant can't get enough sunlight it will die off but unlike humans, plants can't move to go get food or other necessities. Phototropism is a plants way of adapting to sunlight and it deserves to be tested, explored and explained.
The definition of tropism is "a growth movement whose direction is determined by the direction from which the stimulus strikes the plant" and "photo" means relating to light. There for, Phototropism is when a plant grows towards a light source. This is caused by a hormone. A hormone is any of various similar substances found in plants and insects that regulate development. The hormone that causes the plant to grow towards the light is called auxin. Auxin makes the cells divide and the plant to grow. The plant pumps more auxin to the side with the most shade causing the plant to be larger on one side, making the plant bend in the other direction.
The first scientist to ever experiment with phototropism was Charles Darwin. He was born in 1809 and died 1882. In his lifetime he wrote the famous book. On the Origin of Species. In 1880 Charles Darwin and his son Francis Darwin discovered that phototropism would not occur unless most of the plant was shaded. When they …show more content…
shaded the top of the plant phototropism did not occur so the plant stood up straight. However, when they put black sand up to the plants tip the plant would grow towards the light. The Darwins concluded that somehow the tip was causing more growth for the shaded area than the area with light.
Another scientist by the name Boysen Jensen held a phototropism experiment in 1913. Jensen cut the tip off of the tip then covered the tip with gelatin and replaced it. When he did this phototropism occurred. When he used a substance called impervious mica between the tip and the stump, phototropism was prevented. From this he concluded that the shaded area grows faster then the area with sunlight,
Though phototropism was occurring no one at that time knew it occurred because the hormone auxin. The scientist F.W. Went did an experiment that proved some chemical substance caused phototropism. He cut the tips of an Avena sativa and placed them on agar block, a gelatinous material derived from certain marine algae. After several hours he took the agar block and placed it on top of the plant. Growth took place because the auxin was stored in the block then given off to the plant, there for taking the job of the plant tip. All though F.W. Went discovered Auxin it was not known to the world yet as auxin.
The next experiment proved that unequal amounts of auxin causes bending in phototropism.
It was based off Went's experiment but the agar block was placed on one side of the plant and not in the middle. This caused the plant to grow curved. This is because the auxin went all to one side causing it to grow. One side growing faster then another causes the plant to bend. Gravity can cause an unequal amount of auxin. When a tip of a coleoptile is put on an agar block evenly both side of the block will get equal amounts of auxin but if you were to tip the 90 degrees one side of the agar block would receive more auxin then
another.
The ideal plant for an experiment involving phototropism would be a plant with a coleoptile like grass. Any flowering plant or a plant that grows something other then a stem on either side may ruin the results from the experiment.
I modeled my experiment after past experiments but changed some factors to help my results. Since I will not be growing the plants in the spring or summer, I will not use the sun as a source of light for the plants. Also the plants will not be grown outside but inside with a controlled temperature.
When I conduct my experiment I will be using artificial light from a flashlight to simulate the sun. The plant will have light only hitting half of it, which will cause the auxin to be spread more to one side than another. I will do this with five plants. For another five plants I will have even amount of sunlight hitting all parts of the plant causing an equal amount of auxin. For best result I'll keep the light on at all times for all the plants. Twice a day at the same time I will record the plants growth and the angle in which it grows in. I will do this until a week before the due date. Then I will average my data and organize it. After that I will graph it using a line graph. The graph should show the plants growth and tilt over time and how the two groups vary.
Phototropism is a very interesting topic that I think has not been explored enough. Many questions still need to be answered. If it wasn't for Charles Darwin and his son people today would have not noticed there was a thing, such as phototropism. All though phototropism seems to be a minor role in plant growth it plays a major roll. If a plant can't get enough sunlight it will die off but unlike humans, plants can't move to go get food or other necessities. Phototropism is a plants way of adapting to sunlight and it deserves to be tested, explored and explained.