Interactions Between Plant Growth Regulators
1. Auxins and Gibberellins
Auxins and gibberellins exhibit a synergistic effect in promoting growth. Spraying various plants with a combination of gibberellins and auxins at appropriate concentrations promotes stem elongation; the effect of spraying auxins alone is less pronounced than that of gibberellins. A mixture of the two yields superior results.
Auxins and gibberellins display an antagonistic relationship regarding sex differentiation in cucumbers. This antagonism is primarily evident in the control of floral sex: auxins promote the differentiation of female flowers, whereas gibberellins promote the differentiation of male flowers. For instance, if cucumber seedlings treated with auxins are subsequently treated with gibberellins, the effect of the auxins can be negated, and vice versa.
2. Auxins and Cytokinins
The synergistic effect between auxins and cytokinins is manifested in the prolonged duration of cytokinin activity when both hormones are present simultaneously. Cytokinins can enhance the polar transport of auxins, thereby amplifying auxin activity.
The antagonism between auxins and cytokinins is observed in the development of lateral buds in dicotyledonous plants: cytokinins promote lateral bud development, while auxins inhibit it. Regarding the control of apical dominance, a high cytokinin-to-auxin ratio favors lateral bud development, whereas a low ratio maintains apical dominance. However, substances such as kinetin, zeatin, and 6-BA can inhibit the growth-promoting effects of auxins.
3. Auxins and Ethylene
Auxins promote ethylene synthesis by enhancing the activity of ethylene synthase; consequently, high concentrations of auxins inhibit growth. Ethylene influences auxins by inhibiting their polar transport and biosynthesis, as well as by promoting the activity of auxin oxidase.
Excessive levels of auxins induce ethylene production; once the induced ethylene reaches a certain threshold, it inhibits auxin activity. This demonstrates a feedback relationship between the two, and it is precisely this "feedback" mechanism that regulates appropriate plant growth. 4. Gibberellins and Abscisic Acid
Gibberellins and abscisic acid exhibit an antagonistic relationship: gibberellins can break bud or seed dormancy, whereas abscisic acid promotes dormancy. They share the same biosynthetic precursors but are produced under different conditions.
Auxins and gibberellins exhibit a synergistic effect in promoting growth. Spraying various plants with a combination of gibberellins and auxins at appropriate concentrations promotes stem elongation; the effect of spraying auxins alone is less pronounced than that of gibberellins. A mixture of the two yields superior results.
Auxins and gibberellins display an antagonistic relationship regarding sex differentiation in cucumbers. This antagonism is primarily evident in the control of floral sex: auxins promote the differentiation of female flowers, whereas gibberellins promote the differentiation of male flowers. For instance, if cucumber seedlings treated with auxins are subsequently treated with gibberellins, the effect of the auxins can be negated, and vice versa.
2. Auxins and Cytokinins
The synergistic effect between auxins and cytokinins is manifested in the prolonged duration of cytokinin activity when both hormones are present simultaneously. Cytokinins can enhance the polar transport of auxins, thereby amplifying auxin activity.
The antagonism between auxins and cytokinins is observed in the development of lateral buds in dicotyledonous plants: cytokinins promote lateral bud development, while auxins inhibit it. Regarding the control of apical dominance, a high cytokinin-to-auxin ratio favors lateral bud development, whereas a low ratio maintains apical dominance. However, substances such as kinetin, zeatin, and 6-BA can inhibit the growth-promoting effects of auxins.
3. Auxins and Ethylene
Auxins promote ethylene synthesis by enhancing the activity of ethylene synthase; consequently, high concentrations of auxins inhibit growth. Ethylene influences auxins by inhibiting their polar transport and biosynthesis, as well as by promoting the activity of auxin oxidase.
Excessive levels of auxins induce ethylene production; once the induced ethylene reaches a certain threshold, it inhibits auxin activity. This demonstrates a feedback relationship between the two, and it is precisely this "feedback" mechanism that regulates appropriate plant growth. 4. Gibberellins and Abscisic Acid
Gibberellins and abscisic acid exhibit an antagonistic relationship: gibberellins can break bud or seed dormancy, whereas abscisic acid promotes dormancy. They share the same biosynthetic precursors but are produced under different conditions.
