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Articles

Photoperiodic Control of Gibberellin Metabolism in Spinach ¹

MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824

[³H]GA₂₀ applied to spinach plants (Spinacia oleracea L.) was metabolized to several products. Two of these were identified by combined gasliquid chromatography-radio counting as [³H]GA₂₉ and [³H]3-epi-GA₁. Inasmuch as both GA₂₀ and GA₂₉ are endogenous gibberellins in spinach (Metzger, Zeevaart 1980 Plant Physiol 65: 623-626), it was concluded that the conversion of GA₂₀ to GA₂₉ is a natural process. However, 3-epi-GA₁ was not detected in extracts of spinach shoots analyzed by combined gas chromatography-mass spectrometry. This indicates that the conversion of exogenous [³H]GA₂₀ to [³H]3-epi-GA₁ may be an artifact.

Long-day pretreatment of spinach shoots caused a 2-fold increase in the rate of [³H]GA₂₀ metabolism over the rate of metabolism in plants maintained under short-day conditions. Furthermore, [³H]GA₂₉ accumulated more rapidly under long than under short days, whereas photoperiodic treatment had no effect on the accumulation of [³H]3-epi-GA₁. Thus, the long-day-induced increase in the level of endogenous GA₂₉ in spinach shoots (Metzger, Zeevaart 1980 Plant Physiol 66: 844-846) appears to be the result of an increased capability to convert GA₂₀ to GA₂₉.

³ To whom correspondence should be addressed.

¹ Supported by the United States Department of Energy Contract DE-AC02-76ER01338.

This article has been cited by other articles:

				D. J. Lee and J. A.D. Zeevaart Differential Regulation of RNA Levels of Gibberellin Dioxygenases by Photoperiod in Spinach Plant Physiology, December 1, 2002; 130(4): 2085 - 2094. [Abstract] [Full Text] [PDF]