Hormones are chemical messengers synthesized at one location that deliver messages to a different location. Five main types of hormones influence plant growth. Oxin, gibberellin, cytokinin, ethylene, and abscisic acid. Oxin is the hormone that allows plants to bend towards the light. This is called phototropism.
Tropism is the turning of an organism towards an external stimulus. Oxin is synthesized at stem tips and travels downward. That's why, if you remove the stem tip, the plant will lose the ability to grow towards the light.
Oxen makes the plant bend towards the light by moving to the shaded part of the stem. Gibberellins are important at several stages of plant development. For instance, they are required in order for a plant to germinate and are hence upregulated at that time.
They also promote elongation of internodes. aka the stem between nodes which are the spots from which the leaves grow cytokinin counters senescence in plants it is also important in making new plant organs roots vs shoots this hormone is produced in the root apical meristem in other words the tips of roots and is passively carried up with water through the plant's xylem the plant uses the ratio of auxin vs cytokinin to determine if it should form roots or shoots. More auxin promotes the formation of roots, while more cytokinin promotes the formation of shoots. Cytokinin also works with the next hormone we'll discuss, ethylene, to cause the abscission or shedding of leaves, flowers, and fruits. Ethylene, the magical ripening hormone.
If you put a ripe banana in a bag with unripe bananas, the unripe bananas will ripen much more quickly. Ethylene is gaseous, with low solubility in water. It diffuses out of cells, and more of it gets produced by rapidly growing and dividing cells.
This is important for germinating plants, since the high production of this hormone inhibits the expansion of leaves, and allows the shoot to dig upwards through the soil until it reaches light. Abscisic acid is a hormone that signals dehydration. It is synthesized in the chloroplasts of leaves.
When a plant is water stressed, This hormone travels through its xylem and phloem, and causes the leaves to close their stomata to reduce water loss through phototranspiration. These are just five types of hormones that influence plant growth. However, there are many more. If you like this video, please like and subscribe. It would help me make more videos.
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