Learn with steem contest: "Hormones" by @gwillchrist

Hormones are organic substances secreted by the ductless (endocrine) glands in one part of an organism which are essential for proper body function. They are shed directly into the blood stream thus carried to where they affect organs that respond to their actions. Examples of ductless glands found in most vertebrates are:
Pituitary, thyroid, parathyroid, adrenal, pancreas and gonads.

Pituitary gland is located just below the hypothalamus. Normally called the master gland” because its secretions regulate the actions of other endocrine glands. Pituitary gland consists of an anterior part and a posterior part.

Anterior part of pituitary gland secretes several tropic hormones, the growth hormone and prolactin.

Growth hormone: It controls protein metabolism and also promotes normal growth of bones.

Prolactin: It induces milk production in women.

Anti-duretic hormone (ADH): Increases reabsorption of water by kidney tubules and raises blood pressure by constricting arterioles.

Thyroid Stimulating hormone (TSH): It stimulates thyroid gland to secrete thyroxine.

Adrenocorticotropic hormone (ACTH): It stimulates the adrenal cortex to produce its hormones (corticasteroids).

Follicle stimulating hormone(FSH): Causes follicles in the ovary to ripen and produce mature eggs and also initiates sperm formation in testis.

Oxytocin: Induces birth by contraction of uterine muscle.

Luteinizing hormone (LH): Causes ovulation and stimulates secretion of testosterone in testis.

Plant hormones are substance that enhance plant growth. These hormones include auxins, glibberellins, kinins and ethylene.
Auxins are produced at the apical region of roots.

• Promotes lateral bud development Promotes stem elongation

• Auxin stimulates cell enlargement

• Auxin promotes the development of branches, floral and vegetative parts.

• It is produced behind the growing apex.

• Pollen tube growth is stimulated by auxin and its production in developing seeds stimulates fruit set and pericap growth in flesh fruits.

• Auxin interacts synergistically with gibberellin and cytokinnins in stimulation of cell division and in differentiation of the cambium.

• 2-4dichlorophenoxy ethanoic acid and auxin is a normal weed killer at higher concentration.

• Auxin promotes flower formation in growing pineapple.

• Auxin stimulates abscission layer during leaf fall.

• Used as weed -killers or weed control.

• Used in controlling many different phases of plant growth and development.

• Used in controlling flowering and fruiting of plants. Used in initiating adventitious roots in stem cutting.

• Used for breaking seed dormancy.

• Artificial application of auxins delay or prevent the formation of abscission layer, thus, delaying leaf fall.

Other Plant Hormones:

Gibberellins: located in the root and stem apices.

• Stimulates stem growth in dwarf varieties. Induces production of fruit without fertilization.

• Breaks dormancy.

• Retards leaf abscission.

• Induces enzyme’s synthesis in seeds.

Cytokinins: Located in the roots.

• Stimulates cell division.
• Stimulates lateral buds growth.
• Cytokinins delay aging in plant organs. Breaks seed dormancy.

Ethene (Ethylene): Produced in leaves, stems and young fruits.

• Hastens the ripening of fruits.
• Retards lateral bud development.