In order for plants to make the most of their leaf photosynthesis, they have developed a variety of strategies. The direction in which light is coming in will determine the direction of growth, just as it does with houseplants that are placed in a sunny window. Because of this, they are able to meet their requirements for energy through photosynthesis to the greatest extent possible. But who or what is directing this movement in plants? How are the real, immobile plants able to angle themselves toward the sun even though they are located in the darkest shadows?
Proteins, stem cells, and phototropism
It is essential for a plant to direct its growth toward sources of available light while it is still in its immature stages. In the absence of light, many seeds are able to germinate and live off of the starch and fat that they have stored within their bodies. The young plants push their way to the surface of the soil by elongating as much as possible and working against gravity, which serves as their primary source of guidance.
They do this by using light-detecting proteins, which enable them to bend in the direction of the light to find the shortest path to the sunlight. Adult plants are also able to sway in the direction of the light that is the most intense because their stem cells extend more on the side of the plant that is not directly exposed to light. The term “phototropism” describes the process of growth in response to a light stimulus.
Auxin is a hormone found in plants that assists in bending
The well-known scientist Charles Darwin provided the very first in-depth description of plant motion in his seminal work titled “The Power of Movement in Plants,” which was published in the year 1880.
In 1937, the Dutch researcher Frits Went suggested that the hormone auxin, which is found in plants, might play a role in the process of bending in response to light. Even though numerous subsequent findings have supported the idea that auxin is involved in this process, there was a lack of evidence that for that for quite some time.
How it works?
Auxin is the factor responsible for the elongation of these cells. Producing and transmitting this plant hormone is the job of the cells that are located near the tip of the plant shoot. After making its way through the route and stopping at a number of relay stations along the way, it eventually arrives at its final destination, which is the cells on the dark side.
Auxin is transported from one cell to the next by a complicated network of proteins that act as exporters and importers. This allows the Auxin to reach its final destination. In the presence of auxin, cell division is prompted, and the stem of the plant grows in the direction of the light.
However, in the absence of the transport proteins, the hormone will be unable to reach its destination. So, what happens when either of these substances is lacking in the body? By inhibiting the export proteins in plants called “PINs,” it is possible to make a plant less sensitive to light.
Plants like this defy the pull of gravity and continue to grow upward regardless of the direction of sunlight. The same can be achieved by inhibiting the enzyme that was responsible for activating these proteins. And phototropism will once again stop functioning properly. Auxin is the substance that gives plants the power to exhibit phototropism, bending and growing towards the light.