We eat! We walk! We sleep! We react! How come all these happen?

There is particular controlling system in our body for guiding this. But what about the plants? Do they also have this system? Yes such phenomena also occur in plants. As like human being, they also consist of hormones. But their hormones do certain other activities. What kind of activities? That’s I am going to tell you here. There are basically five kinds of Plant hormones or Phytohormones. Names are auxin, cytokinin, gibberellins, abscisic acid & ethylene. Stick to this article & read what they actually do.  


Term auxin is derived from word auxein (Gk. Meaning ‘to grow’). Auxin is the key hormone who is responsible for cell elongation in phototropism & gravitropism. Differentiation of the meristem into vascular tissue is also controlled by this hormone. It helps in promoting

Differentiation of the meristem into vascular tissue is also controlled by this hormone. It helps in promoting leaf development & arrangement.

One of the most significant functions regulated by auxins is apical dominance.  It involves inhibition of lateral buds more of the auxin production in apical meristem. Some of the other functions controlled by auxins are flowering, fruit, setting, inhibition of abscission & other many of the responses of plants.

Auxins are of two types; naturally occurring & synthetic.

WHO-1Synthetic auxins are used as herbicides. Synthetic Auxins promotes flowering in tomato. Some of the examples are given in picture. 

You must have heard about IAA (indole acetic acid). It is natural auxin. IAA shows physiological activities. It is basically a rooting hormone.

Auxin also promotes parthenocarpy. Movement of auxin is unidirectional i.e. from top to bottom. Concentration of auxin is more at the top of the plant. Consequently auxin causes apical dominance. Growth of lateral buds is suppressed in this case.

You know what? When the apical part of a plant is cut; even apical dominance is also removed.


Certain effects of gibberellin are as like that of auxin. You know gibberellin is not a single hormone but it is a group of hormone or chemicals.

You know how it was invented? Rice pants grew taller & fell over. On studying it was observed that they have been infected by a fungi viz. Gibberella fujikuroi. This fungus was producing certain kind of chemicals which were causing growth.  Yes they were gibberellins!

Gibberellins promote stem elongation by increasing length of internodes. You can consider example of sugarcane. Obviously, for obtaining more amount of sugar, we need to have more yields. We can also have canes of good length. For that we require gibberellins. 🙂

Gibberellins also help in germination, flowering, fruit ripening as well. Gibberellins are like growth hormones secreted by Pituitary gland in human.

They help in fruit growth. They basically affect intracellular activities as in protein formation by the process of transcription.

They help in overcoming genetic dwarfism as well. Why not? It is increasing length after all. You know they are found to be very active in inducing parthenocarpy as well. They are even more effective in inducing parthenocarpy as compare to auxins.


Do not confuse it with cytokines which are types of immune cells.

Cytokinins are also a group of hormones which help in cell division.  Resultantly it helps in making new plant organs. Actually, it helps in production of certain proteins which help in mitosis.

WHO-2Cytokinins are also produced apical part and moves towards other part of plant.  And you know one more thing, this movement is passive. It doesn’t need energy.

One more important function controlled by Cytokinins is delaying senescence.  They also control repair mechanism of plant. 

Let me tell you one more thing, auxin & cytokinins are antagonistic hormones. It means they function oppositely. If the concentration of both hormones is equal then normal plant growth occurs. If auxin concentration is more as compared to cytokinin, then rooting will occur. On the other hand if concentration of cytokinin is more then shoot formation will occur.


WHO-3Did you ever notice that if a basket is having really ripe brown banana with green banana, the unripen banana will turn yellow at a faster rate. How this happens? This whole story moves around a hormone, ethylene. The interesting thing about this hormone is that it is volatile. It can evaporate easily & can affect nearby fruits in the form of a gas. Cool no?


When do we drink water? Obviously, when we feel thirsty. During the time when we feel dehydrated, we have to drink water. In same way, when stress condition occurs in plant, a hormone is released.

You know what, even one plant give signal to another plant regarding the stress & all of them start forming Abscisic acid. This hormone is usually found in dried leaves. It can move in all of the direction in plants.

You know what stomata do in a plant right? When there is scarcity of water, they are closed. How do they get this signal? Well this is Abscisic acid which is taking up this signal to guard cells for closing of the stomata.

Knowledge cannot be limited in words. This is just a drop from the sea. Want to look at sea of information? Jump in to the link.

You can find pool of biology here.

You can find PCM material as well at this link.

Well guys! This is Anjali Ahuja; signing off for now 🙂

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