Auxin synthetic

Synthetic auxins Phenoxyalkanoic acids Benzoic acids Pyridinecarboxylic acids Quinolinecarboxylic acids 4... 

The stimulatory effect of auxin on ethylene biosynthesis is the basis for the use of synthetic auxins (Figure 5.11) to promote the abscission of... 

Naphthyloxy)acetic acid Figure 5.11 Synthetic auxins... 

Synthetic auxin or plant hormone, plant growth regulator... 

Many of the same conclusions may be drawn from results with synthetic auxins as from indole-3-acetic acid water intake increased, there was a lessening of the downward translocation of photosynthate with temporary increases of soluble carbohydrates in the leaves, and alterations appeared in the metabolic ratq and direction and in enzyme activity. However, the direct site of action is not known, and many of the effects are puzzling. n-Fructose oligosaccharides in artichoke and chicory storage-tissue were diminished by 70% (calculated on the content of dry matter) in 6 days... 

Two aliphatic acids possess, for grasses, many of the growth-distortion and toxicity effects associated with the synthetic auxins on dicotyledonous plants. Trichloroacetic acid and 2,2-dichloropropionic acid (dalapon), as the sodium salts, have been called grass "hormones or auxins, although Wilkinson184 could find no growth stimulation at low concentrations, and described dalapon as an antiauxin from its interference with indole-3-acetic acid effects. The herbicidal properties of trichloroacetate do not depend on its protein-denaturing ability, and those of 2,2-dichloropropionic acid involve, at least indirectly, the synthesis of pantothenic acid. 

There is little published information of interest to carbohydrate chemists concerning the benzoic acid herbicides. The predominant member, 2,3,6-trichlorobenzoic acid, inhibited uptake and utilization109 of acetate-14C. It shows some auxin-like properties, whereas 2,3,5-triiodobenzoic acid appears to block the transport of natural and synthetic auxins, and has often been termed an antiauxin. The triiodo compound inhibited oxygen (86% at... 

Application of ethylene-,4C to plants resulted in only a 2.4% conversion into soluble carbohydrates, 11% into ether-soluble materials, 6.9% into phytol, 31.7% into cellulose and lignin, and 9.6% into soluble protein and non-protein material, mainly phosphates. 9 Treatment of detached fruit (such as apples, bananas, peaches, figs, and pears) with synthetic auxins, especially (2,4,5-trichlorophenoxy) acetic acid, speeded up ripening, as indicated by color, taste, softness, and starch breakdown. 7 Other fruits have been similarly ripened, 8 and the treatments are effective both on climacteric and non-climacteric fruit. 

Many synthetic auxins have been produced, including 2,4-dichIoro-phenoxyacetic acid or 2,4-D naphthalene-l-acetic acid and 2,3,6-trichlorobenzoic acid, among others. Used as a herbicide. 2.4-D is described in Herbicides. 

This may be confirmed by the fact that silatrane derivatives of synthetic auxins resistant to lAA-oxidase are practically as active as auxins themselves (Table 29). 

Nakamura, A., Higuchi, K., Goda, H., Fujiwara, M. T., Sawa, S., Koshiba,T., Shimada, Y., and Yoshida, S. (2003). Brassinolide induces IAA5, IAA19, and DR5, a synthetic auxin response element in Arabidopsis, implying a cross talk point of brassinosteroid and auxin signalhng. Plant Physiol. 133,1843-1853. 

Synthetic auxin (acting like indolylacetic acid)... 

The variety of aldehyde oxidases discovered in other plants have similarities to the maize enzyme, but also have some very important differences. Enzymes contained in a cell wall fraction from barley seedlings were able to oxidize IAAld to form IAA at a pH optimum of 7 and Km of 5 pmol 1 1, which was very similar to the enzyme found in maize.113 Two aldehyde oxidases from potato have also been identified 101 they had a similar pH optimum (between 7 and 8), but preferred aliphatic aldehydes to aromatic aldehydes. Although oat and cucumber aldehyde oxidases have been shown to oxidize IAAld to produce IAA,102 114 the oat enzyme had a lower pH optimum and higher Km than the maize enzyme, and the cucumber enzyme was inhibited by synthetic auxin and activated by 2-mercaptoethanol, which was not true for the maize enzyme. The difference in the enzymes makes it difficult to envision a common evolutionary origin for the IAAld pathway in plants if these particular enzymes are involved in each case. 

Of the analogous compounds related to a particular hormone, attention must be drawn to the large group of synthetic auxins, to the synthetic cytokinins (- recently not only adenine, but also urea derivatives -) and to the ethylene generators ( 1, 2). An extension of the range of analogous compounds is indicated in the case of abscisic acid, as well (3j. 

Auxins Synthetic Auxins Triiodobenzoic acid Hydroxyfluorene carboxylates... 

Figure 1. Structures of natural auxin, indole-3-acetic add, and synthetic auxin herbicides and auxin transport inhibitors (phytotropins) belonging to the different chemical families.

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