Theory:

We have learnt that the movement in plants is based on the stimulus and is either slow or fast.
 
Important!
The responses to the stimuli will occur at a faster rate only if the information transfer occurs quickly. For this, it requires a medium of transmission which moves at a faster rate.
What is chemical communication?
 
The electrical impulses are an excellent mode for faster cell-to-cell communications. Due to some limitations, it will occur only within the neurons. Along with the electrical impulses, the neurons use some chemical messengers for communications, known as chemical communication.
1024px-Neuronal_Synapse.jpg
Chemical communication in animal cells
What are hormones?
The electrical and followed by chemical communications not observed in plant cells as they lack nervous tissue. Instead of impulses, the stimulated cells release a chemical compound that diffuses throughout the organism's body. The other cells detect these released chemicals using the special molecules on their surfaces that will be recognized and transmitted. And, these chemicals are known as hormones.

Let us study the various hormones secreted in plants and their importance.
The word hormone is derived from the Greek word "hormone", meaning "to excite", "to stimulate", "impulse".
Hormone_Transport.png
Transportation of hormones in plants and animals
Plant hormones:
The control and coordination in plants are carried out by these chemical substances in plants known as plant hormones or phytohormones.
These phytohormones and are transported to different parts of the plants to perform various physiological functions.
These are organic molecules produced in low concentrations in plants, controlling various morphological, physiological, and biochemical responses.
Types of plant hormones:
Plant hormones can be classified as five major classes. They are as follows:
  1. Auxins
  2. Cytokinins
  3. Gibberellins
  4. Abscisic Acid (ABA)
  5. Ethylene
In accordance with growth auxins, cytokinins and gibberellins are the plant hormones that promote plant growth; abscisic acid and ethylene inhibit plant growth.
 
YC Editorial - Divya (18).png
Hormonal interaction in plant growth and development
  
It stimulates the formation of an abscission zone in leaves, flowers, and fruits, leading to premature shedding.
Reference:
https://en.wikipedia.org/wiki/Hormone#/media/File:Hormone_Transport.png
https://commons.wikimedia.org/wiki/File:Plant_microbiota.png
https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Neuronal_Synapse.jpg/1024px-Neuronal_Synapse.jpg