Endocrine System

Hormones are chemicals secreted by various endocrine glands directly into the blood and transported to the respective organs, where they act by regulating various metabolic processes. The organ affected by the hormone is called the target organ. The target cells have specific receptors to recognize the respective hormones.

There are two types of glands present in our body.

Endocrine Glands– These glands that do not have ducts and transport their secretions directly to the site of action through the blood, e.g. adrenal glands, pituitary glands, etc.

Exocrine Glands– These glands have ducts to pass their secretions, e.g., sweat, liver, etc.

Hormones are secreted by endocrine glands.

What is Plant Hormones?

Plants need sunlight, water, oxygen, minerals for their growth and development. These are external factors. Apart from these, there are some intrinsic factors that regulate the growth and development of plants. These are called plant hormones or “Phytohormones”.

Plant hormones are chemical compounds present in very low concentration in plants. They are derivatives of indole (auxins), terpenes (Gibberellins), adenine (Cytokinins), carotenoids (Abscisic acid) and gases (Ethylene).

These hormones are produced in almost all parts of the plant and are transmitted to various parts of the plant.

They may act synergistically or individually. Roles of different hormones can be complementary or antagonistic.

Hormones play an important role in the processes like vernalisation, phototropism, seed germination, dormancy etc. along with extrinsic factors.

Synthetic plant hormones are exogenously applied for controlled crop production

Charles Darwin first observed the phototropism in the coleoptiles of canary grass and F.W. Went first isolated auxin from the coleoptiles of oat seedlings.