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LU6: Plant Growth Regulation, : - Coggle Diagram
LU6: Plant Growth Regulation
Several distinctively different groups of compounds are recognised as triggering substances
Auxins,cytokinins, Gibberellins and Phenolics.
Auxin and Cytokinin contain nitrogen.
Abscisic acid, gibberellins, ethylene are composed of carbons, hydrogen and oxygen.
Environmental factors such as light and temperature, interact with the phytohormones and biochemical processes during growth and differientiation.
Growth Regulators & Hormones
Growth regulators are triggering substances involved in the excitement of the biochemical reactions.
Leading to changes in chemical composition within the plant.
Major Plant hormones-auxins,cytokinins,gibberellins (control growth direction). Abscisic acid and ethylene survival hormones tend to inhibit growth.
Hormones are specific organic substance, effective in low concentration, synthesized by cells in one part of plant, then transported to another part of plant.
Physiological effects of hormones which differ from time to time, species to species and more particularly; tissues to tissues.
Hormones are use effectively in low concentrations, and many are toxic when they are use in high concentrations.
Roles& function PGR
Cell differentiation
Auxin influence differentiation of vascular tissue in the elonging shoot.
Wedge-cut is made in the stem of Coleus plant to severe and remove parts of the vascular bundles.
New vascular tissues will be formed from cells in the pith and connect with the bundles in the uncut regions.
Cambium growth
Auxin promotes the growth of the calcium in woody plants.
Auxin moves down from the shoot tip and stimulates cambium cells to divide and forming secondary phloem and secondary xylem.
Root growth
Auxin promotes the formation of adventitious roots in cuttings. Cuttings made from selected parts of woody plant species.
Application of a large quantity of auxin to roots already growing will inhibit the growth of the roots.
Fruit Growth
Auxin promotes the growth of fruits by treating female flower parts of certain species.
Within the flower, the developing seeds are a source of auxin.
Leaf abscission
In old leaves, other parts of the plant occurred with a diminished production.
Among other factors, under many circumstances, abscission can be prevented by the application of auxin.
Control of weeds
Synthetic auxin, 2,4-D and its chemical deriavates are widely use commercially to control weeds in agriculture.
Auxin applied in high concentration and thereby is toxic and killed the weeds.
Roles&Function Cytokinins
1) cell division
Leaf Senescence
3) Organ Formation in tissue culture
Roles and function of Ethylene
1) Fruit ripening
Abscission
3) Sex expression
Roles and function Abscisic acid
Vegetative buds
Tolerance to stress conditions
Closing of stomata
Roles and function Gibberellins
1) Stem Elongation
Produce dwarf Mutants
2) Juvenility in plants
Induce flowering
Overcome Dormancy
Stimulate pollen and fruit development
Hormones are biologically active in extremely small amounts
Chemically related to certain components of nucleic acid
Ethylene is a gas ti produce by the incomplete combustion of hydrocarbons.
Gibberellins overcome dormancy and enable the seeds to germinate.
Effects of plant hormones depend largely on the target tissues and the chemical environment in which these tissues are located.
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