| | 1 | Author
| U. Margna, T. Vainjärv | Requires cookie* | | | Title
| Kinetin-Mediated Stimulation of Accumulation of Buckwheat Flavonoids in the Dark  | | | | Abstract
| A short treatment o f excised buckwheat cotyledons with a solution o f kinetin lead to an up to 9-fold stimulation o f anthocyanin biosynthesis, to an about 50 percent increase in the accum ula tion o f rutin, and to an about 30 percent increase, on the average, in the accum ulation o f C-glycosylflavones in the treated material during its posttreatment incubation in the dark. When the treated cotyledons were incubated in a solution o f L-phenylalanine anthocyanin accum ulation in the dark practically attained the same high level as it was observed in the illum inated cotyledons fed with exogenous L-phenylalanine. In experim ents with 14C-labelled L-phenylalanine kinetin induced a sharp rise in the labelling (resp. in the utilization o f exogenous substrate for biosynthesis) o f anthocyanins and rutin in the dark and a slight increase in the radioactivity o f C-glycosylflavones. Similar labelling changes occurred in the illum inated cotyledons. However, both kinetin and light still more effectively prom oted biosynthetic use o f the endogenous sub strate. As a result the relative portion o f flavonoids formed from exogenous L-phenylalanine under these conditions showed a decrease as com pared with the ratio o f precursor use in the un treated cotyledons. The results show that low accum ulation rates o f anthocyanins and other flavo noids in the dark are conditioned by the lim ited access o f substrate (L-phenylalanine) m olecules to the flavonoid enzymes lending further support to the idea that flavonoid biosynthesis is normally controlled at the substrate rather than at the enzym ic level. | | | |
Reference
| Z. Naturforsch. 38c, 711—718 (1983); received May 2 1983 | | | |
Published
| 1983 | | | |
Keywords
| Anthocyanins Flavonoids, Accum ulation Kinetin, [l4C-L]Phenylalanine, Fagopyrum esculentum | | | |
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| default:Reihe_C/38/ZNC-1983-38c-0711.pdf | | | | Identifier
| ZNC-1983-38c-0711 | | | | Volume
| 38 | |
| 2 | Author
| U. Margna, L. Laanest, E. Margna, T. Vainjärv | Requires cookie* | | | Title
| L-Tyrosine as a Precursor of Flavonoids in Buckwheat Cotyledons | | | | Abstract
| Exogenous L-tyrosine was incorporated 1 3 -1 4 tim es less effectively than exogenous L-phenyl-alanine into flavonoids in excised cotyledons o f 3 days old buckw heat seedlings but proved to be an only 5 times poorer precursor when the experim ents were carried out with 5 days old material. Simultaneous administration o f L-phenylalanine m arkedly reduced incorporation o f L-tyrosine into flavonoids. A similar decrease in the utilization o f exogenous L-tyrosine for flavonoid b io synthesis occurred in kinetin-treated cotyledons. H owever, in cotyledons treated with high doses o f glyphosate, an inhibitor o f the shikim ic acid pathway, an increase in the formation o f flavonoids from exogenously supplied L-tyrosine was observed. Under all conditions the relative incorporation rate o f exogenous L-tyrosine was highest for anthocyanins and lowest for C-glyco-sylflavones while within the latter class o f com pounds the luteolinic derivatives orientin and iso-orientin incorporated more label than their apigeninic analogues vitexin and isovitexin. PAL and TAL activities were found to be present in the cotyledons in a ratio o f 50:1. The possible role o f L-tyrosine as an alternative natural precursor for the biosynthesis o f flavonoids and other related polyphenols is discussed. | | | |
Reference
| Z. Naturforsch. 40c, 154 (1985); received April 24/O ctober 29 1984 | | | |
Published
| 1985 | | | |
Keywords
| Anthocyanins, Flavonoids, Biosynthesis, [14C-L]Tyrosine, [14C-L]Phenylalanine, Kinetin, Glyphosate, Fagopyrum esculentum | | | |
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| default:Reihe_C/40/ZNC-1985-40c-0154.pdf | | | | Identifier
| ZNC-1985-40c-0154 | | | | Volume
| 40 | |
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