Die Aktivität von einigen freien und konjugierten Gibberellinen im Triticum-Halbkaryopsen- und Amaranthus-Gibberellintest

Abstract

Summary The biological activity of several gibberellin (GA) conjugates was studied and compared with that of the corresponding free GAs. The following conjugates were included: 3-O- β -D-glucopyranosides of GA 1 , GA 3 and GA 4 ; 13–O- β -D-glucopyranosides of GA 1 , GA 3 and GA 5 ; GA 8 -2-O- β -D-glucopyranoside; 13-O- β -D-glucopyranosyl- GA 5 - β -D-glucopyranosyl ester; GA 3 - β -D-glucopyranosyl ester and GA 3 - α -D-glucopyranosyl ester; N-GA 3 -oyl-glycine, N-GA 3 -oyl-glycylglycine and N-GA 3 -oyl-proline. The activity was determined in the wheat- α -amylase bioassay, i. e., a special modification of the barley endosperm bioassay, and the Amaranthus GA bioassay using sterile techniques. Activities of the free GAs as well as of the conjugates differ in both bioassays. Many of the GA conjugates were found to possess very low activity. Only the 13-O-glucopyranosyl-GA 5 - β -D-glucopyranosyl ester was as active as GA 5 in Triticum , whereas in Amaranthus GA 5 -13-O-glucoside and GA 4 -3–O-glucoside showed relative activities of 7.5 and 15 %, respectively. The GA 3 - β -D-glucopyranosyl ester reached relative activities of 10–15% in both bioassays. According to the present knowledge the activity of GA conjugates as measured in the bioassays is based upon the presence of enzymes hydrolyzing the glucoside, glucosyl ester, and amide-like linkages.