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Questions and Answers
What is the function of p-Chlorophenoxyisobutyric acid (PCIB) in relation to auxin?
Which compound strongly promotes the photooxidation of IBA and IAA?
What is the primary function of 1-Aminocyclopropane-1-carboxylic acid (ACC) in plants?
What is the role of aminoethoxyvinylglycine (AVG) in plants?
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Which compound inhibits polar auxin transport?
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What is the impact of compounds that inhibit cytokinin synthesis?
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Study Notes
Auxins and Cytokinins
- Main auxins: indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), Picloram, Dicamba, and p-chlorophenoxyacetic acid (CPA)
- Main cytokinins: zeatin (Z), zeatinriboside (ZR), isopentenyladenine (iP), 6-benzylaminopurine (BAP), 6-furfurylaminopurine (kinetin), and thidiazuron (TDZ)
Plant Hormone Action in Plant Tissue Culture
- Callus tissue is generated from leaf explants of Arabidopsis halleri and Arabidopsis thaliana
- Friable callus is produced and transferred to shoot regeneration media, followed by root regeneration media
- The final step is the removal of the fully regenerated plants to the greenhouse
- Friable callus can also be used to generate stable cell suspension cultures
Plant Hormones (Growth Regulators)
- Hormones are "chemical messengers" influencing plant development
- Plant hormone: a natural substance produced by plants that acts to control plant activities
- Classical plant hormones: Auxin, Gibberellins, Cytokinins, Abscisic Acid, and Ethylene
- New generation plant hormones: Brassinosteroids, Salicylic acid, Jasmonic acid, Peptides, and Polyamines
Auxin and Cytokinin Function
- Auxin is produced in the apex and upper part of the stem and transported downwards
- Auxin and cytokinin penetrate the axillary bud and inhibit and promote outgrowth, respectively
- Cytokinin is produced in the roots and transported upwards in the stem
- Strigolactone (SL) reduces auxin transport capacity, inhibiting axillary bud outgrowth
Effects of Hormones in Tissue Culture
- Auxin:
- Formation of meristems of adventitious roots
- Induction of somatic embryos
- Cell division and callus formation
- Inhibition of outgrowth of axillary buds
- Cytokinin:
- Stimulation of outgrowth of axillary buds
- Inhibition of shoot elongation
- Inhibition of leaf senescence
- Promotion of cell division and callus formation
- Gibberellin:
- Release from dormancy in seeds, somatic embryos, apical buds, and bulbs
- Inhibition of adventitious root formation
- Synthesis-inhibitors promote root formation
- Ethylene:
- Ripening of fruits
- Promotion or inhibition of adventitious regeneration
- Maturation of somatic embryos
- Facilitation of acclimatization
- Abscisic acid:
- Inhibition of root growth
- Promotion of the development of dormancy
Modulators of Hormone Metabolism, Action, or Transport
- 2,3,4-Triiodobenzoic acid (TIBA) and 1-N-naphthylphthalamic acid (NPA) inhibit polar auxin transport
- p-Chlorophenoxyisobutyric acid (PCIB) inhibits auxin action
- Phenolic compounds (e.g. ferulic acid or phloroglucinol) inhibit auxin oxidation
- Lovastatin inhibits cytokinin synthesis
- Paclobutrazole, ancymidol, and flurprimidol inhibit gibberellin synthesis
- 1-Aminocyclopropane-1-carboxylic acid (ACC) is a precursor of ethylene
- Aminoethoxyvinylglycine (AVG) inhibits ethylene synthesis
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Description
Test your knowledge on plant hormones by identifying main auxins and cytokinins such as indole-3-acetic acid, zeatin, and more. Learn about the functions and characteristics of these important plant growth regulators.