Vegetable Hormones

What are

In vegetables the response to stimuli is not mediated by the nervous system but by hormones.

As in all other organisms, the response of a plant to internal and environmental stimuli takes place in three stages: perception, transduction and response.

In general, perception occurs when a stimulus interacts with its receptor. This phenomenon somehow triggers transduction, that is the conversion of the stimulus into a form capable of influencing the phenomena that occur in a cell. In this passage a second intracellular messenger often intervenes.

Usually the response of a plant to plant hormones involves the activation of genes responsible for the synthesis of specific proteins or other metabolic changes

Functions

Plant hormones are the chemical messengers that preside over the internal coordination of the plant's various functions and regulate responses to external stimuli. They are produced in a part of an organism and influence its other parts disproportionately regarding their concentrations.

If for example a plant is subjected to water stress, a hormone is released from the mesophyll chloroplasts, the abscissic acid, which goes to reach the stomata and stimulates them to close, thus limiting breathing, and allowing the plant to adapt to the new environmental condition

Difference between animal and plant hormones

1. There are no specialized organs in a plant to produce hormones: the production centers are multiple and difficult to locate

2. Plant hormones do not always act in a place other than that of production.

3. Each plant hormone has a wide range of activities and therefore acts on numerous organs with different functions; consequently every vegetable organ is regulated by more hormones
4. The action of a plant hormone varies from one organ to another. The diversity of effects resides in the presence of receptors for the hormone in more organs; however, these receptors lead to different transduction chains that trigger different chemical reactions.
5. While animal hormones are chemically polypeptides or steroids, plant hormones are small molecules with varied structure

6. . Plants have a lower number of hormones, the main ones are in fact only 5 ( auxins, ethylene, abscissic acid, gibberellins and cytokinins ).
7. One thing in common between animal and plant hormones is low concentration action. The effect of the hormone begins to manifest itself beyond a certain threshold concentration; increasing the concentration also increases the effect up to an optimal concentration at which there is the maximum effect. If the optimal concentration is exceeded, the effect decreases again. However in animals the hormonal action can be graduated through small variations of concentration, in plants instead it takes variations of the order of 1000-10000 times
8. In animals the action of hormones is regulated by a rigid system: most of the endocrine glands are regulated by the pituitary gland, which, in turn, is controlled by the nervous system. In plants, coordination is less hierarchical and there is no single center that controls the production and secretion of all hormones.