Ethylene auxin and

Wample, R.L. and Reid, D.M., The role of endogenous auxins and ethylene in the formation of adventitious roots and hypocotyl hypertrophy in flooded sunflower plants (Helianthus annuus), Physiol. Plant.,... 

Souter, M., Topping, J., Pullen, M., Friml, J., Palme, K., Hackett, R., Grierson, D. and Lindsey, K. (2002) Hydra mutants of Arabidopsis are defective in sterol profiles and auxin and ethylene signaling. Plant Cell, 14,1017-31. 

A major factor leading to abscission is the weakening of the middle lamella, cell walls, or cells in a separation zone across the petiole, pedicel, or stem. Although any of the known plant hormones can alter the progress of abscission, ethylene remains unique as the principal stimulus of the increased activity of wall-degrading enzymes in abscission, whereas auxin can be given a central role in the retardation of abscission. With the present level of understanding, it would seem that abscission control involves interactions between auxin and ethylene. 

In some cases it might be desirable to inhibit ethylene synthesis chemically to prevent responses mediated by naturally produced ethylene or stress-produced ethylene. Although some substances do inhibit ethylene production modestly—e.g. TIBA (69)—no outstanding regulator of this nature has been discovered. Another possibility is to promote or inhibit ethylene action. Promotion can be accomplished by auxin transport inhibitors and GA in cases where auxins and ethylene have opposite effects 52, 53, 54, 55). Recently, silver ion was found to be a potent inhibitor of ethylene action (70). Ethylene action also can be inhibited by lowering the temperature and O2 level or increasing the CO2 level... 

Epstein, E., Sagee, O., Cohen, J.D., Garty, J., 1986. Endogenous auxin and ethylene in the lichen Ramalina duriaei. Plant Physiol. 82, 1122-1125. 

CHAE, H.S., CHO, Y.G., PARK, M.Y., LEE, M.C., EUN, M.Y., KANG, B.G., KIM, W.T., Hormonal cross-talk between auxin and ethylene differentially regulates the expression of two members of the 1-aminocyclopropane-l-earboxylate oxidase gene family in rice Oryza sativa L.), Plant Cell Physiol., 2000, 41,354-62. 

Subsequent work with lAA indicated that this auxin which was produced at the terminal bud stimulated cellular growth in the terminal bud but as it was transported down the shoot, somehow supressed growth of the lateral buds (22). There are indications that under the influence of auxin, the cells around lateral buds produce ethylene. It is the ethylene in turn which inhibits the growth of the lateral buds (23). When the terminal bud is removed and the auxin and ethylene are no longer present, the lateral buds grow, resulting in bushy plants. The number of flowers on the plant is also increased. 

Burg SP, Burg EA (1966) The interaction between auxins and ethylene and its role in plant growth. Proc Natl Acad Sci USA 55 262-269 Burrows WJ, Carr DJ (1970) Cytokinin content of pea seeds during their growth and development. Physiol Plant 23 1064-1070... 

Epstein E, Sagee O, Cohen JD, Garty J (1986) Endogenous Auxin and Ethylene in the Lichen Ramalina duriaei. Plant Physiol 82 1122... 

It has been evidenced that auxin and ACC stimulate ethylene production in some lower plants, for example, in the moss Funaria hygrometrica and in the ferns Pteridium aquilinum and Matteuccia struthiopteris Moreover, ethylene synthesis via the ACC-dependent pathway and in the presence of endogenous ACC and its conjugate in marine unicellular Acetabularia algae was reported. Probably during the evolution of land plants, a relatively primitive pathway of ethylene production was replaced by the ACC-dependent synthesis pathway that now predominates. 

Most species of angiosperms produce hermaphroditic flowers. The unisexuality in some plants most often results from developmentally programmed abortion or selective reduction in sex organ primordia. In dicots, higher levels of auxins, cytokinins, and ethylene usually correlate with female sex expression and in most of them the femaleness is mainly promoted by ethylene. ... 

The pathway of ethylene biosynthesis in higher plants is from l-methionine4 (Figure 5.9). Methionine is an intermediate in other metabolic processes and the control of ethylene biosynthesis via the interference of methionine production is not realistic. The ACC synthase step from S-adenosyl methionine to ACC appears more susceptible to chemical modification auxin promotes ethylene production by increasing the activity of ACC synthase. Subsequent steps from ACC are less controlled and ethylene is readily produced from the conversion of ACC in most tissues. 

A relationship was found between the auxin present and ethylene evolution, and it has been suggested that acceleration of abscission may be due to ethylene. 0... 

Ethylene as a stimulator of growth and development. The most observed actions of ethylene on growing plants involves growth inhibition, or acceleration of senescence. These actions are especially evident in the antagonism or opposition of ethylene to auxins, gibberellins and cytokinins (27), as already outlined above. Actually ethylene stimulates growth in many types of cells, especially in water plants (Table II). When ethylene acts to stimulate cell elongation, as in water plants, auxins and CC>2 enhance the ethylene effect (38,39). This interaction is the reverse of that observed on land plants wherein ethylene opposes the effects of auxin, GA3 and cytokinins. 

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