Phototropism in our Plants

Over the course of the year, there have been a few attempts by our biology classes to grow plants within our crowded classroom. First we worked with fast plants, which grew extremely quickly as the name suggests, then pansies, and we have now moved on to plant an assortment of morning glories and moonflowers. As the morning glories and moonflowers are beginning to develop however, it is plain to see that as their stems shoot up they don’t grow straight, but in a curved line. What is especially fascinating about this pattern of growth is that although the other plants we have grown were placed in similar conditions, except those being used in experimental groups, none of the other groups of plants seemed to have such an intense tendency to slant as they matured. The fast plants we grew did tilt slightly, but not to the same degree as the morning glories and moonflowers being grown now. Below are two images, on the left are fast plants and on the right are some of our moonflowers and morning glories:

Fast Plants Moonflowers and Morning Glories

The phenomenon we are noticing is not unprecedented, in fact we learned about it during our studies this year, and it is called phototropism. Phototropism is the potential of a plant to elongate to move towards or away from light. This process works because plants produce a hormone called auxin, which promotes the elongation of coleoptiles, in their tips and then spread it to their other cells. When there is only one light source the hormone spreads unevenly throughout the plant, accumulating on the dark side and causing it to grow more quickly, resulting in the curve of the plant.

The direction that our plants are leaning is consistent with the explanation of what phototropism is since our plants are growing towards the window, which has a greater source of light than what can be found in the classroom. Still, it is peculiar that these plants are sitting under grow lights, which are artificial lights designed to stimulate plant growth by emitting wavelengths of light sufficient for photosynthesis, and surrounded by light from the windows and the classroom, yet they arch to one of these three light sources that surround them. An even more peculiar question to pose is why did the other plants we grow not arch to the window when they were subject to the same conditions? Do we keep the classroom lights off more than we did during other times of the year because the temperature is so high and we want to remain cooler? Is the fact that it is summer in our part of the world and we have a more direct angle towards the sun changing our results? Are the grow lights not on as consistently as they were during other times of the year? Or maybe the shorter amounts of daylight that we experienced earlier in the year caused the plants to rely more on the artificial lights than the current plants do, resulting in straight as opposed to curved growth.

All of these questions can be overwhelming, but it is the nature of scientists to be curious and pose questions from their observations. As Albert Einstein once said "The important thing is to not stop questioning. Curiosity has its own reason for existence." If scientists were not able to formulate questions and quandaries from the information they gathered, then no new theories or hypothesis would ever arise, and there would be no need for experiments to support or disprove new ideas. Essentially, science would not exist as it does today because there would be a halt in the flow of ideas and experimentation. Scientific discoveries would stop. And although so many unknowns is a lot to process and analyze, forcing oneself to answer them allows a person to realize details that they might have otherwise overlooked. In the case of explaining the phototropism in the morning glories and moonflowers for example, after asking all of these questions I remembered that the grow lights were lower when the fast plants were growing, which could account for the fast plants not having as extreme of a slant. Moonflowers and morning glories also grow on vines, which means that the slant the plants have exhibited thus far could represent the tendency vines have to bend and twist. 

Hopefully more investigation will be able to yield a definitive answer to the cause of phototropism in our plants before the end of the year, but whatever the cause it is remarkable that we are able to see some of the information we learned about in our biology class develop on its own before our eyes.