Cinnamic acids, auxins

Inhibition of PAL-activity in vivo should result in the reduced accumulation of metabolites derived from cinnamic acid. Light-induced anthocyanin formation was used as an indicator of the in vivo production of cinnamic acid, as the anthocyanin content of a tissue can be determined by rapid and simple procedures. All compounds tested reduced the production of anthooyanins in isolated hypocotyls incubated in the light, but in these experiments a-NAA showed a nearly tenfold higher inhibitory activity as compared with B-KAA. This result clearly indicates that the action of auxins on anthocyanins exists, but is not very specific. 

Secondary metabolites, produced by pathways derived from primary metabolic routes, are numerous and widespread, especially in higher plants. More than 20,000 were known in 1985 (Hartmann, 1985), and at least 1000 additional compounds, are described each year. In practice, the difference between the primary and secondary metabolites is fuzzy. Plant hormones such as gibberellic acid, indoleace-tic acid (auxin), ethylene, kinetin, and abscisic acid, as well as compounds involved in plant cell wall structure such as cinnamic acid and its polymeric derivative, lignin, are intermediate between primary and secondary metabolism (Birch, 1973). In some instances, compounds normally considered primary metabolites may accumulate in large amounts and behave in a manner usually associated with secondary metabolites. Entities such as shikimic acid and squalene, which initially were considered secondary metabolites, were subsequently shown to be important intermediates in the formation of primary metabolites (phenylalanine, tyrosine and tryptophan, and steroids, respectively). 

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