give description of plant and animal hormone?

Asked by Meenu S Unnithan | 18th Sep, 2014, 08:31: AM

Expert Answer:

Plant Hormones: Plant hormones control some aspects of the growth of plants such as cell division, cell enlargement and cell differentiation.



1. Auxins

  • Promote growth of plants.
  • They are secreted by the cells present at the tip of stems and roots.
  • Therefore, auxins control the phototropic and geotropic movements of plants.
  • Auxins accelerate growth of stems but reduce the growth in roots.
  • Synthetic auxins are used in horticulture.

2. Gibberellins

  • Promote cell differentiation in the presence of auxins.
  • They break seed dormancy.
  • They also break dormancy in buds.
  • Stimulate elongation of shoots.

3. Cytokinins

  • Promote cell division in plants.
  • Delay ageing of leaves.
  • Promote opening of stomata.
  • Promote fruit growth.

4. Abscisic Acid

  • Acts as a growth inhibitor.
  • It promotes dormancy in seeds and buds.
  • Promotes closing of stomata.
  • Promotes abscission, i.e. wilting and falling of leaves.
  • Detachment of flowers and fruits from the plants is due to abscisic acid.
Hormones in Animals: They are secreted by different endocrine glands.




1. Adrenaline

Produced by the adrenal glands.

  • Adrenaline prepares the body for the fight and flight mechanism.
  • When excited or in anger, the adrenal glands produce a lot of adrenaline.
  • It speeds up heart beat and breathing.
  • It raises the blood pressure.
  • Blood supply to the digestive system and skin is reduced, and the blood supply to the skeletal muscles is increased.


2. Thyroxine

Secreted by the thyroid gland.

  • Regulates carbohydrate, protein and fat metabolism.
  • It increases the basal metabolic rate (BMR).
  • It regulates body growth such as ossification of bones and mental development.

Simple goitre:

  • It is caused by iodine deficiency.
  • Iodine is necessary for the synthesis of thyroxine.
  • In this disorder, the gland is enlarged which is prominent due to swelling in the neck.

3. Growth Hormone (Somatotropin)

Secreted by the anterior lobe of the pituitary gland.

  • It is essential for normal growth.


  • Due to the deficiency of growth hormone.
  • The growth of bones and other body organs is slow.


  • Due to the oversecretion of growth hormone.
  • The bones grow long.
  • Such a person giants up to 2.7 metre in height.

4. Insulin

Secreted by pancreas

  • Regulates the blood glucose (sugar) level.

Diabetes Mellitus


  • High concentration of sugar in blood (hyperglycemia).
  • Excretes large amount of urine containing more concentration of sugar.
  • A person feels thirsty due to constant loss of water through urination.
  • The person loses weight and becomes weaker.
  • Sometimes, the person may lose vision.


It cannot be cured, but sugar levels can be maintained by the administration of insulin.

5. Testosterone

Secreted by the testes in males.

  • Controls the development of sex organs in males.
  • Controls the development of secondary sexual characters during puberty.


6. Oestrogen

Secreted by the ovaries in females.

  • Controls the development of female sex organs.
  • Controls the development of secondary sexual characters during puberty in females.



Answered by Hemangi Binny | 18th Sep, 2014, 09:20: AM