Co-ordination and Control in Plants, Biology tutorial


Coordination in plants is very easy than in animals. It is completed by a chemical termed as plant hormonest.  They are just alike to animal hormones in that they just required in small quantity to bring about their consequences. Thus generated in one portion of the body and transported to the other portion where they apply their effects (positive or negative). Animal hormones are generated in particular glands and bring around much specific responses in particular target organs. In plants, hormones are not generated in tissues specialized just for their production, their results are as well more general, differing with concentration and kinds of target organ. Chemically too, plant hormones are not associated to animal hormones, however they are organic compounds.

Plant hormones almost for all time stimulate or restrain growth in the target tissues in responses to the external stimuli like temperature, light, day length, gravity and touch. As an outcome, they are as well termed as plant growth substances; however they influence other activities like fruit formation, root growth and falling of leaf.

Plant Hormones:

The development of plants to a vast extent is regulated through hormones. Such chemical substances (or hormones) influence the plants within whereas factors like temperature, light, water and gravity affect the plant externally. Hormones are required in small amounts. They are prepared in some regions and diffuse to other portions to generate some special effects.

The main or renowned plant hormones are: Auxins, Gibberelins, Floregens, Cytokinins, Abscissic acid, Ethene (ethylene), Traumatin, Dormin, Formin and so on.


Naturally the mist significant occurring Auxin is indole acetic acid (IAA). It is generated at apices of shoots and is carried in one direction away from the tip. It moves across the short distances through diffusion and longer distances by means of phloem.

Effects or Functions of Auxin on Plant:

The effects or functions of Auxin on plant comprise the given:

1) Rapid growth of shoot: Auxin is recognized to cause the shoots of plants to grow rapidly.

2) It causes apical dominance: Auxin is recognized to cause the development of plants at the apices.

3) Prevention of Lateral growth: Auxins generated in the terminal bud stimulates the development or elongation of the main stem, whereas at the similar time move down to the shoot to restrain (prevent) the growth of lateral buds. Therefore, the terminal bud controls the rest of the shoot so as to make sure that energy for the growth of the main stem is not wasted thus generating a tall plant with short lateral branches.

4) Auxin and fruit growth:

Once a flower is fertilized, Auxin are generated and sent to the ovary causing fast growth of the ovary as it grows into fruits. The presence of Auxin as well prevents the formation of abscission layer at the base of the stalk of flower. This will assist fruits to reach ripening phase. When the fruits are ripened, Auxin supply to the flower stalk is decreased and abscission layer is made leading to the falling of the fruit.

5) It breaks dormancy in seed: Auxin uniformly promotes or assists to break dormancy in seed therefore making sure their early on germination.


Gibberellins are generated in young foliage leaves and roots, apices of roots and stems and also in the embryo.

Functions or Effects of Gibberellins:

1) Gibberellins stimulate fast stem elongation in dwarf plants and other plants which experience little stem elongation.

2) It persuades the growth of fruits devoid of fertilization.

3) It stimulates the augmentation of roots.

4) Dormancy in buds and seeds are broken if gibberellins are released to them.

5) Stimulating the embryos in the germination of seeds to generate enzymes which hydrolyze starch keeps in the seeds.


Cytokinins are generated in roots, embryos and fruits which are actively experiencing growth. Cytokinins are as well growth promoting hormones such as Auxin and gibberellins.

Functions or Effects of Cytokinins:

1) It can stimulate the growth of roots.

2) It controls the cell division.

3) Encourage flowering in certain plants.

4) Encourage fruits growth in certain plants.

5) Assist in breaking the dormancy in certain seeds.

6) Aid to retard the onset of ageing in leaves by maintaining the nucleic acid and protein synthesis.

7) It raises resistance of certain plant to harmful effects like radiation, viral infections and low temperature.

Abscisic Acid:

The abscisic acid is a hormone generated in mature green leaves, fruits and root caps. This is a growth inhibitor whose consequences usually resist those of Auxin, gibberellins and cytokinins.

Functions or Effects of Abscisic Acid:

1) It represses the growth of buds.

2) It persuades dormancy (especially if environmental situations are unfavorable).

3) It brings around ageing in leaves.

4) It might play some roles in the abscission.

5) It restrains mitosis in the vascular cambium.

6) It controls the closing and opening of the stomata.

Ethene (or Ethylene) Gas:

Ethene gas is a simple hydrocarbon generated in stems, leaves and young fruits.

Functions or Effects of Ethene:

1) It slows down lateral bud growth.

2) It speeds up the ripening of fruits.

3) It slows down the stem elongation.

4) It accelerates abscission of flowers, fruits and leaves.

5) It accelerates the ageing of organs of plant.


Floregens are found in fruits and flowers of plants - Most of the botanists are convinced that the flower initiation is an outcome of a hormonal influence and the tentative name floregen has been assigned to the kingdom material.

Functions or Effects of Floregens:

1) It mainly controls the initiation of flowers in the plants.

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