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PLANT GROWTH REGULATORS - Coggle Diagram
PLANT GROWTH REGULATORS
Triggering substances=phytohormones
biochemical reactionsand changes in chemical composition within the cells, tissues and organs of the plant.
Auxins, Cytokinins, Gibberellins and Phenolics
(Ethylene).
PGR = Biostimulants = Bioinhibitors
act inside plant cells to stimulate or inhibit specific enzyme or enzyme systems to regulate plant metabolism
naturally produced in plants to control the growth and other physiological functions
synthesized by cells in one part of the plant and
then is transported to another part of the plant
specific organic substance, effective
in low concentrations.
Physiological Effects of Hormones
Auxins
ROLE
Cell Enlargement: It stimulates cell enlargement and stem growth
Cell Division: It stimulates cell division in cambium. Used in tissue culture plant production in combination with Cytokinin.
Vascular Tissue Differentiation: It stimulates differentiation of phloem and xylem.
Root Initiation: It stimulates root initiation on stem cuttings. Used in plant propagation by tissue culture for development of roots.
Apical Dominance: It suppresses the apical shoot growth and promotes the growth of lateral buds.
FUNCTIONS
Auxin influences the differentiation of vascular
tissue in the elongating shoot.
Auxin promotes the growth of the cambium in
woody plants
Auxin promotes the formation of adventitious
roots in cuttings.
Auxin promotes the growth of fruit: By treating, the female flower parts of certainspecies with auxin, it is possible to produceparthenocarpic fruit (fruit produced without fertilization)
abscission can be prevented by the application of
auxin
The auxin is applied in a high concentration and
thereby is toxic and killed the weeds
Cytokinins
Prevent leaf senescens
Cytokinins have been isolated from many different species of seed plants where they are found primarily in actively dividing tissues, including seeds, fruits and roots.
Organ Formation in Tissue Culture
Abscissic Acid (ABA)
Stomata Closure: Water shortage brings about increase in ABA level, leading to stomata closure as a response to water stress.
Growth Inhibiters: ABA inhibits shoot growth but has less effect on root growth.
GA Counteracts: ABA counteracts the effect of gibberellins on a-amylase synthesis in germinating cereal grains.
Induced Dormancy: ABA affects induction or maintenance of dormancy in seeds.
Gibberellins
Stem growth: Gibberelic Acid (GA) causes hyperelongation of stems by stimulating both cell division and cell elongation. This results in taller plants.
Bolting in long day plants: GA cause stem elongation in response to long days
Induction of seed germination: GA activates germination of seeds which otherwise require cold (stratification) or light to induce germination.
Enzyme production during germination: GAstimulates the production of enzymes like amylase in germinating cereal grains
Ethylene
Fruit Ripening: Ethylene in the form of gas helps ripens fruits under natural conditions.
Induction Of Femaleness: Promotes production of female flowers in cucurbits (cucumber, squash,melon) to increase the yield.
Flower Opening: Promotes flower initiation and controlled ripening in pineapples.
Leaf and Fruit Abscission: Accelerates fruit abscission for mechanical harvesting in fruit crops such as grapes, cherries, and citrus.