| Auxin |
- Cell elongation |
- Synthesized primarily in apical meristems |
Polar transport |
- Binding to receptor proteins in cells |
- Rooting hormones, herbicides, and plant growth regulators |
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- Apical dominance |
and young leaves |
(basipetal and |
- Activation of AUX/IAA genes |
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- Root development |
- Derived from tryptophan amino acid |
acropetal) |
- pH changes in cell walls |
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- Tropisms (e.g., phototropism, gravitropism) |
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| Gibberellin |
- Stem elongation |
- Synthesized in shoot tips and young leaves |
Non-polar transport |
- Binding to specific receptors in cells |
- Promoting stem elongation, improving yields |
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- Seed germination |
- Complex enzymatic pathway |
(both acropetal and |
- Activation of gene expression |
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- Flowering regulation |
|
basipetal transport) |
- DELLA protein degradation |
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- Fruit development |
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| Abscisic Acid |
- Stress response |
- Synthesized in various plant tissues |
Diffusion and |
- Binding to specific receptors in cells |
- Enhancing stress tolerance, seed dormancy |
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- Stomatal regulation |
- Derived from carotenoids |
vascular transport |
- Activation of stress response genes |
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- Leaf abscission |
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- Regulation of stomatal closure |
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- Seed dormancy |
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- Promotion of leaf senescence |
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| Ethylene |
- Fruit ripening |
- Synthesized mainly from methionine |
Gas (diffusion) |
- Binding to specific receptors in cells |
- Ripening of fruits, promoting senescence |
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- Senescence |
- Enzymatic reactions |
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- Activation of transcription factors |
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- Leaf abscission |
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- Stress response |
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| Cytokinin |
- Cell division and growth |
- Synthesized in roots, young leaves, seeds |
Xylem and phloem |
- Binding to specific receptors in cells |
- Promoting cell division, shoot and root development |
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- Shoot development |
- Conversion of AMP to various cytokinins |
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- Activation of cell division-related genes |
- Used in plant tissue culture, improving crop yield |
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- Root development |
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- Nutrient uptake |
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- Delay in senescence |
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