Totipotency in Plants Apical Meristems & Lateral Meristem Function
Totipotency in Plants
The capability to form a full-plant from a single cell. Plants that are totipotent can regenerate their cells or tissues, which is plants’ ability to replace themselves through natural growth. If a plant cannot regenerate, it will not grow as well as those who do have the capability. Some plants are more totipotent than others, with some being able to regenerate any cell in their body while other types can only form new stems.
The regeneration process in plants is how plants replace their cells, tissues, and organs. After being damaged, trees have formed the ability to repair themselves. This efficiency of the plant’s self-repairing system differs from animals as animals do not have cells that can be regenerated.
Regeneration, therefore, gives plants a greater advantage over animals because it can be more efficient when it comes to growing back its parts or shedding them. While this is a benefit for plants, it could be considered a negative thing for animals. Animals did not evolve the ability to replace their organs. Some scientists believe that increased efficiency would put plants ahead of animals, leading to some animals being crowded out.
This ability is due to the large number of stem cells that are present in plants. When a part of a plant is damaged, stem cells will be activated and replace that part, enabling the plant to grow back quickly and perfectly healthy again. It has been found that all plants, even after severing their roots from the plant, can grow back and replace all of the cells in their roots.
After a plant is cut or damaged, the phytohormone auxin is produced. This hormone allows for cell division and development rather than proliferation. Because of this, cell proliferation stops, and all-new cells produced become either apical meristems or lateral meristems.
Apical meristems will give rise to new tissues, while lateral meristems will grow to replace lost parts of the plant. This auxin production and the movements of lateral and apical meristems are called “the shoot apical dominance system” by Auxin.
Auxin, also known as indole-3-acetic acid (IAA), is a hormone that is responsible for controlling plant growth and development. Auxin is most prevalent in plants’ root systems, but it can also be found in leaves and the stem. Auxin moves from the root up to the shoot, affecting how fast new cells will form in shoots.
Auxin is usually produced by meristems (specialized structures that contain a high concentration of intact cells) but can also be formed secondarily through secretion from injured or damaged cells. Auxin proteins are responsible for binding to auxin response elements (AuxRE) present on the cell’s genetic material. Auxin also controls whether cells are formed apically or laterally.
Apical meristems function
Apical meristems are important for plant growth because they will produce growing points and new stems. Apical meristems will divide to form new cells, which will become differentiating cells. As this process occurs, the new cells are pushed further away from the apical meristem, forming a primary axis. The cells will then differentiate into tissues and organs of the plant.
What are the lateral meristem functions in plants?
Lateral meristems are responsible for growing plant tissues and building any new structures that may be needed to replace those that are damaged or severed. Lateral meristems do not have distinct growth regions like apical meristems do, simply growing in a direction determined by the outermost cell’s movement. If a branch is severed, lateral meristems will grow to replace its lost tissue.
Like “Apium graveolens,” some plants have been found to be able to replace an entire root system if it is severed from the plant’s body. The root cells are totipotent and will multiply and replace all the cells in the root initially.
In “Nicotiana rustica,” it has been found that individual cells can act as the main axis, initiating new growth and not being replaced by laterals or other meristems. An example of this is shown by the formation of a flower stalk. The main shoot grows from a single cell that will become the main axis.
This cell then divides into 4 cells surrounding it, which will become laterals. Once these laterals are formed, they grow in length and form flowers on their ends, known as the “initiation stage.” This process happens in only one bud and only once in an entire plant’s life.
More recently, it has been shown that a plant can produce two apical meristems, which will form two laterals on either side of the plant. One of the laterals will then grow up and out of the plant’s surface to become a series of fruit (or reproductive structures) while the other reaches into the root system to continue growth. This is an example of “co-option” because one lateral will be used to replace an entire root, while another will take over for that portion of the root system.