Gibberellin ethylene production

There also have been clear indications that interactions of ethylene with auxins, cytokinins, gibberellins and ABA are involved in both ethylene production and action. Generally the effects of ethylene tend to antagonize those of auxins, cytokinins and gibberellins, and tend to reinforce those of ABA, depending, however, on tissue systems involved. Reinforcement of ethylene by ABA and vice versa occurs more frequently in senescence. 

At the preclimacteric stage of development, just prior to the rise in ethylene production the concentrations of auxins, gibberellins, and cytokinins are assumed to be very low. 

Brassinosteroids are reported to stimulate overall plant growth and development, especially under stress conditions, to enhance auxin-induced growth as well as auxin-induced ethylene production (5, 6). Brassinosteroids interact with most of the phytohormones, such as cytokinins and gibberellins, and in particular with auxin. 

Frenkel C (1972) Involvement of peroxidase and indoleacetic acid oxidase isozymes from pear, tomato and blueberry fruit in ripening. Plant Physiol 49 757-763 Fuchs Y, Lieberman M (1968) Effects of kinetin, lAA and gibberellin on ethylene production and their interactions in growth of seedlings. Plant Physiol 43 2029-2036 Fuente RK de la, Leopold AC (1972) Two components of auxin transport. Plant Physiol 50 491-495... 

Fuchs Y, Lieberman M (1968) Effects of kinetin, IA A, and gibberellin on ethylene production and their interactions in growth of seedlings. Plant Physiol (Bethesda) 43 2029-2036... 

The most commercially successful PGRs are those that operate either through the inhibition of gibberellin biosynthesis, from mevalonic acid (Knee, 1982) or through the production of ethylene. These represent the two most valuable pathways for growth modification since they have key roles in extension growth, ripening, fruit set and dominance. 

Auxins (67), gibberellins (68), cytokinins (69), and abscisic acid (67) can enhance the production of ethylene if added in concentrations that are generally considered stronger than tissue levels. Paradoxically, ethylene was one of the first chemicals identified as a potent defoliant (70), and now it has been shown to be a natural product of plant tissues that seems to regulate abscission (68, 71) as well as an influence on a host of other physiological reactions (7). 

Chloro-3-methyl-4-nitro-lH-pyrazole (Release) has no auxin-, gib-berellin-, or cytokinin-like activity, yet it is an ejffective abscission agent. At the present, there is no evidence to indicate that Release retards auxin, gibberellin, or cytokinin activity. It does stimulate and enhance the tissue production of ethylene (105). Release is fairly stable, and there is no indication that it is degraded by the tissue to ethylene per se (106). 

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