By Andrew Shim
Subheading: Ways plants grow towards a direction based on stimulus such as light or touch.
Have you ever left a plant next to the windows and a few days later you see them grown towards a certain direction? The following phenomenon is tropism. Tropism is a directional growth of an organism in response to various stimuli. The following phenomena are most commonly observed in plants. The following phenomena start with the receptors within plants noticing a certain direction having a better environment, which increases the possibility of survival of plants. Then, they immediately go to action in which the following receptors and their associated signal pathway affect the density of auxins within plants (a plant hormone and will be discussed later). The change of the density of auxin in a certain area is directly correlated with the direction of growth the plant will take, which leads to the most optimal environment in which the plant can flourish.
Tropism may commonly occur due to many factors, where some factors include light, touch, water, gravity, chemicals, humidity, and much more. The most common type of tropism is phototropism, which is a phenomenon that occurs due to the stimulation of light. The following process is done in several stages. The initial stage is first, the cells that are furthest away from the ground detect the presence of light towards a certain direction. The second stage is the receptors and its associated signal pathways within plants receive such information and distributes the hormone auxin, which induces growth, towards the other side of the light source that has been detected. Afterward, the auxin that has been mostly distributed to the other side activates the growth of the following cells, which makes the cells elongate and makes the plant bend towards the side of the stimulus.
Another type of tropism is thigmotropism, tropism that occurs due to the stimulus of touch, is often used to control the growth direction of plants in crops which are often used to prevent plants’ competition over water, nutrients, and sunlight. It is also used to direct plant’s growth and prevent them from falling down due to weight such as in tomato plants, in which they often lean towards a certain direction as they grow due to its increased weight on the high part of the plant, but using thigmotropism (placing a stick next to the plant so the plant can grow onto it), the plant can grow properly straight, which maximizes their potential of gaining sunlight which directly correlates to the harvest rate of tomatoes.
In conclusion, tropism is a phenomenon that happens to all plants in order for them to maximize their survival rate in case of change in environment, in which the plants specifically grow toward a certain direction in which the following direction leads the plant to the best conditions for them to grow. Due to the following trait of plants, the concept of tropism is often used in agricultural affairs, in which farmers control the direction of growth in order to purposely make fruits grow towards the following direction to facilitate their work.
References
Encyclopædia Britannica, inc. (n.d.). Auxin. Encyclopædia Britannica. Retrieved from
Encyclopædia Britannica, inc. (n.d.). Phototropism. Encyclopædia Britannica. Retrieved from
Encyclopædia Britannica, inc. (n.d.). Tropism. Encyclopædia Britannica. Retrieved from
Guilfoyle, T., & Hagen, G. (1970, January 1). Auxin Signal Transduction. ScienceON. Retrieved
From
Phototropism. Phototropism - an overview | ScienceDirect Topics. (n.d.). Retrieved from
“Tropism.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,
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