Subject(s)
Plant Growth Regulators/chemistry , Plant Growth Regulators/metabolism , Abscisic Acid/chemistry , Abscisic Acid/metabolism , Amides/metabolism , Brassinosteroids , Cholestanols/chemistry , Cholestanols/metabolism , Cyclopentanes/chemistry , Cyclopentanes/metabolism , Cytokinins/chemistry , Cytokinins/metabolism , Esters/metabolism , Gibberellins/chemistry , Gibberellins/metabolism , Glucosides/biosynthesis , Indoleacetic Acids/chemistry , Indoleacetic Acids/metabolism , Oxylipins , Steroids, Heterocyclic/chemistry , Steroids, Heterocyclic/metabolismABSTRACT
In order to determine the significance of the C-6 carboxyl group for the biological activity gibberellin A3, 6-epigibberellin A3, 7-norgibberellin A3, 6ß-methyl-7-norgibberellin A3, and 7-homogibberellin A3 were studied using dwarf pea, dwarf maize, dwarf rice, dwarf barley and α-amylase bioassays. All gibberellin A3(GA3)derivatives tested were considerably less active than GA3. In all biossays, 6-epi-GA3 showed a low activity of the same order, whereas 6ß-methyl-7-nor-GA3 was inactive. Surprisingly, 7-nor-GA3 had some activity in the dwarf rice (root application), dwarf barley, and α-amylase bioassay, in contrary to its low potency in the dwarf pea, dwarf maize, and dwarf rice (micro drop) bioassay. 7-Homo-GA3 was primarily active in the dwarf maize, dwarf barley and dwarf rice bioassay. It also caused antigibberellin effects in dwarf rice. The results demonstrate that the C-6 carboxyl group is not absolutely essential for biological activity of gibberellins. The different activities of 7-nor-GA3 observed in the various test systems may indicate that the C-6 carboxyl group is a structural requirement more for uptake and/or transport processes than for receptor affinity.
ABSTRACT
(-)-Jasmonic acid was identified as a plant growth inhibitor of the pericarp of Vicia faba by means of gas-liquid chromatography, high resolution mass spectrometry, (1)H-nuclear magnetic resonance ((1)H-NMR), and (13)C-NMR. Additionally, the pericarp contains very small amounts of abscisic acid (ABA) and 4'-dihydrophaseic acid. The highest level of jasmonic acid was reached prior to full pericarp length. This amount (3 µg g(-1) fresh weight) is similar to the maximal ABA content in the developing seed. Jasmonic acid is a plant growth inhibitor possessing a relative activity in the wheat seedling bioassay of 1-2.5%, compared to ABA. Contrary to ABA, jasmonic acid does not cause retardation of leaf emergence. The possible physiological role of jasmonic acid in the pericarp is discussed and compared with the assumed function of ABA in developing seeds.
ABSTRACT
The biological activity of several gibberellin (GA) conjugates was studied and compared with that of the corresponding free GAs. The following conjugates were included: O(3)-ß-D-glucopyranosides of GA1, GA3 and GA4; O(13)-ß-D-glucopyranosides of GA1, GA3 and GA5; O(13)-ß-D-glucopyranosyl-GA5-ß-D-glucopyranosyl ester; GA3-ß-D-glucopyranosyl ester and GA3-α-D-glucopyranosyl ester; N-GA3-oyl-glycine, its methyl ester, N-GA3-oyl-glycylglycine, and N-GA3-oyl-proline. All compounds were synthesized chemically but some of them are known to occur as endogenous plant products, or to be formed in plants upon application of a free GA. Activity was determined in the dwarf pea, dwarf corn, dwarf rice, and lettuce hypocotyl bioassays. The GA conjugates were found to posses different relative activities depending on the chemical structure, the bioassay system, and the site of application (shoot or roots). It is concluded that the activity of GA conjugates as measured in different bioassays is based upon the ability of plant enzymes and possibly of certain microorganisms to hydrolyze glucosidic, glucosyl ester, and amide-like linkages.
