Phenol derivatives, in higher plants

Figure 1. Biosynthetic pathway for production of shikimic acid pathway-derived phenolic compounds in higher plants.

Many herbicides and other chemicals have been reported to influence levels of various phenolic compounds in higher plants by unknown mechanisms. It is unlikely that more than a few of these compounds have a primary influence on secondary phenolic compound synthesis. For instance, in our survey of the effects of 17 herbicides on anthocyanin accumulation, only glyphosate appeared to directly influence accumulation (31). The effects of several compounds on secondary phenolic compound production for which the mechanism of influence is unknown are summarized in Table II. A much longer list could be derived from the literature. Unfortunately, many of these compounds are phytotoxic or are known to have effects other than on secondary aromatic compound production. In most cases the effects on these compounds correlate well with extractable PAL activity (31, 71, 72, 73, 74) (Figure 5), even though they do not directly affect the enzyme. 

Phenol-carbohydrate derivatives, in higher plants, 20, 371-408 Photochemistry, of carbohydrates, 18, 9-59 Physical chemistry, of carbohydrates, 15, 11-51 of starch, 11, 335-385 Physical properties, of solutions of polysaccharides, 18, 357-398... 

Pridham, J. B., Phenol-Carbohydrate Derivatives in Higher Plants, 20, 371-408... 

Phenol-carbohydrate derivatives, in higher plants, 20, 371-408 Photochemistry, of carbohydrates, 18, 9-59... 

J. B. Pridham, Phenol-carbohydrate derivatives in higher plants, Adv. Carbohydr. Chem., 20 (1965) 371 08. 

The pathways of carbon flow in eukaryotes are more complex than in prokaryotes, mainly because the C2 units produced within mitochondria can be exported (e.g. for lipid biosynthesis) only as part of a citrate unit produced in the citric acid cycle. The branch point in carbon flow to either isoprene or acetate can lead to additional isotopic fractionation. In general, it seems that n-alkyl hpids in a particular organism are depleted in 13C by c. 1.5%o relative to isoprenoids produced from the same substrate (Hayes 1993). In higher plants, the phenolic precursors of lignin derive from glucose (Fig. 2.29), so it is not surprising that the carbon isotopic composition of lignin reflects the major photosynthetic pathway involved (C3 or C4 Benner et al. 1987). 

Bryophytes, constituents of (constituents of mosses). Bryophytes produce numerous secondary metabolites that have not yet been found in other plants. They are mostly phenolic compounds and terpenes, there are considerable differences between the individual classes of mosses. Homworts (Anthocerotae) are characterized by the presence of lignans, liverworts (Hepaticae) principally by terpenes, especially sesqulterpenes that are often enantiomers of the compounds found in higher plants and bibenzyl derivatives. Mosses (Musci) contain biflavonoids (see flavonoids), sphagnorubins (peat mosses) and cou-marin derivatives. Alkaloids are rare and have as yet only been found in liverworts. 

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