The native gibbereilins (GAs) of various organs of the Avena plant were analyzed by bioassay and gas chromatography-mass spectrometry (GC-MS) after silicic acid partition column chromatography. The major GA of the inflorescence was identified as GA3 by GC-MS, and this GA also forms the major component of the nodes, p-i internode, and roots as determined by GLC or chromatography/bioassay. The inflorescence and nodes are the major sources of native GAs, the last two leaves, internode, and roots having dgnificantly lower amounts of GA-like substances. In the internode, less polar GAs predominated at the lag stage of development, whereas by the log and plateau stages, the more polar GAs increased significantly.Since less polar GAs are early in oxidative interconversion sequences, this fnding indicates sequential conversion to more polar and probably more active GAs, during log phase growth of the p-i internode.Excised stem segments of Avena plants are known to be very sensitive in their growth response to exogenously supplied gibberellins (GAs), especially GA, and GA3 (13,15). In contrast, they show no significant growth promotion by other plant hormones such as IAA, kinetin, and ABA (14). In light of this marked specificity of oat stem segments to GAs, especially the more oxidized GA, and GA3, it is germane to ask the following questions: Where in the Avena plant are the primary sources of native GAs that may be regulating internodal elongation in situ? Are these GAs produced mainly in the internodes, or are they derived from other parts of the plant? What are the predominant forms (i.e. degree of oxidation) of GAs found in the Avena plant during rapid internode elongation?Past studies on native GAs in other cereals are relevant to the present investigation. Radley and co-workers (12, 21, 22) have characterized GA1-and GA3-like substances in barley by means of TLC, fluorimetry, and bioassay. Faull et al. (9) reached similar conclusions for barley GAs using paper, TLC, GLC, paper electrophoresis, and bioassay. Murphy and Briggs (18) identified GA3 and GA7 in germinating barley by novel means using crystallization to constant specific radioactivity with unlabeled carrier GA methyl ester after initial methylation of the endogenous GA with '4C-diazomethane. By techniques they estimated GA3 levels to be 1.5 ng/grain, a level which correlates well with bioassay estimates. Faull et al. (10) showed that 11-day-old barley seedlings synthesized an A,-like GA de novo from 14C02, and that the labeled GA was metabolized within 12 hr, implying a high rate of turnover of GAs in the seedlings. Nicholls (19) found very high levels (15 to 48 Ag/g, dry weight) of GAs in barley inflorescences.In the present study native GAs of Avena nodes, internodes (at 3 stages of elongation), roots, leaves, and inflorescences are analyzed by silicic acid partition column chromatography, being quantitated by bioassay, and in certain cases, GLC. Identification of one GA was made by GC-MS.4 These analyses have allowed the questions pose...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.