Metabolism of Tritiated Gibberellins A4 and A9 in Norway Spruce, Picea abies (L.) Karst.

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Abstract
Shoots of mature grafted propagules of Picea abies (L.) Karst. metabolized [3H]gibberellin A4 (GA4) to at least 14 acidic substances, two of which were tentatively identified by gas-liquid radiochromatography as GA2 (possibly an artifact) and GA34. [3H]GA9 was converted into a number of metabolites, one of which was chromatographically similar to, but not identical with, GA4. Metabolism was maximally 61 and 57% over 48 hours for GA4 and GA9, respectively, and was correlated with the rate of change (i.e. increase followed by decrease) in endogenous GA-like substances as shoot elongation progressed. Propagules covered with a clear plastic film, a treatment which promotes flowering, metabolized [3H]GA4 more slowly than did control plants in the open. Inasmuch as a GA4/7 mixture can also promote flowering in P. abies, the retarded metabolism of [3H]GA4 may reflect the manner in which trees under plastic metabolize endogenous GA-like substances. If so, then the stimulating effect of this cultural treatment on flowering may come about through an increased level of endogenous, less polar GA-like substances.