Uptake of Gibberellin Methyl Esters by Spores and Induction of Dark Germination in Lygodium japonicum :
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In the fern Lygodium japonicum, the effect of the exogenous application of two gibberellin methyl esters, gibberellin A_4 methyl ester (GA_4Me) and gibberellin A_<20> methyl ester (GA_<20>Me) on spore germination in the dark and uptake of GA_4Me and GA_<20>Me by spores was investigated. Tritiated GA_4Me and GA_<20>Me were prepared and used as radioactive tracers. The activity of GA_4Me was more than 100-fold that of GA_<20>Me for the induction of spore germination. When treated for 24 h, the activity for inducing spore germination remained after removal of the gibberellin methyl esters from the medium. The amount of GA_4Me taken up by spores was more than three times that of GA_<20>Me throughout the 24 h time course of treatment. The uptake of both gibberellin methyl esters was proportional to the external concentration for the range of concentrations between 10^<-9> M and 10^<-6> M. When treated with the tritiated gibberellin methyl esters at 10^<-6> M and 10^<-7> M for 24 h, most of the gibberellin methyl esters taken up by the spores were not metabolized. Although the uptake of the two gibberellin methyl esters differed by 3- to 5-fold, their abilities to induce spore germination differed by more than 100-fold. Therefore, the difference in the activity of the two gibberellin methyl esters regarding the induction of spore germination could not be explained solely by the difference in their uptake.
- Plant and cell physiology
Plant and cell physiology 29(6), 913-918, 1988
Japanese Society of Plant Physiologists