plant hormones

• Plant growth regulators are substances that coordinate plant growth, development, and responses to environmental stimuli. • They include hormones such as Auxins, Gibberellins, Cytokinins, Abscisic acid, Jasmonic acid, and Ethylene.

• Auxins are the first plant hormones discovered. • They are involved in apical dominance, cell elongation, gravitropism, and the remobilization of nutrients. • They are produced in meristematic regions and growing organs.

• Auxins are synthesized from tryptophan in three steps. • They exist in two forms: Free form (active form, moves freely). Conjugated form (inactive, released after enzymatic hydrolysis).

• Gibberellins are diterpenoid compounds involved in cell division and elongation, seed dormancy breakage, and bolting in response to long days. • They are synthesized in developing seeds, fruits, and young leaves.

• Gibberellins are synthesized from acetyl CoA via the mevalonic acid pathway. • They are poorly understood in terms of transport and are found in both phloem and xylem.

• Cytokinins regulate the cell cycle, promote cell elongation, and delay senescence. • They are mainly produced in the roots and work with auxins in morphogenesis.

• ABA regulates stomatal movement, seed dormancy, and inhibition of growth. • It promotes water uptake by roots and induces resistance to water stress.

• Ethylene is a gaseous hormone produced by all plant organs. • It regulates fruit ripening, senescence, flowering, stem elongation, and defense responses to stress.

• Jasmonic acid is synthesized from linolenic acid. • It induces resistance to insects and diseases, alters pollen development, and works in concert with ethylene to modulate responses to wounding.

• PIN proteins are involved in auxin transport, orienting asymmetrically in plant cells. • They help regulate polar auxin transport, a key mechanism in various physiological processes like apical dominance and cell elongation.

• Inducing parthenocarpic fruit production. • Malting of barley by promoting fermentation and enzyme production.

• Ethylene is transported as a volatile gas and soluble form in the phloem and xylem. • It regulates ripening, senescence, flowering, and responses to stress and wounding.

• Jasmonic acid and ethylene work together to regulate responses to stress and pathogen attacks. • They both promote defense mechanisms and influence plant growth and development.