
%0 Journal Article
%A Wiseman, Nadine J. 
%A Turnbull, Colin G. N. 
%T Endogenous gibberellin content does not correlate with photoperiod-induced growth changes in strawberry petioles
%J Functional Plant Biology
%D 1999/07/29
%V 26
%N 4
%P 359-366
%K 
%R https://doi.org/10.1071/PP98002
%U https://www.publish.csiro.au/paper/PP98002 
%X We have examined whether gibberellins (GAs) mediate photoperiodic growth responses in strawberry (Fragaria &#215; ananassa) by measuring GA content and GA metabolism in petioles with accurately defined growth rates. Gibberellin A1 , GA8 , GA19 , GA20 , GA29 , GA34 , and tentatively GA17 , were identified by gas chromatography&#8211;mass spectrometry, and GA4 was detected by selected ion monitoring. Although petiole growth rates were reduced within 2 d of a long-day to short-day transfer, we found no consistent changes in GA content until 8 d, when GA1 , GA8 , GA29 and GA34 were reduced by about two-fold in short days. GA20 concentration was always low regardless of age or treatment, typically 10-fold less than GA1 and 40-fold less than GA19 . Application of paclobutrazol (25 g plant&#8211;1 ) reduced growth rate by 43%, somewhat greater than the effect of short days (23%), but resulted in a six-fold decrease in GA1 content, much greater than the maximum two-fold effect of short days. However, paclobutrazol-treated petioles in long and short days differed in growth rate by 30%, yet had no difference in GA1 content. &#91;2H&#93;GA19 and &#91;2H&#93;GA20 were metabolised to GA1 , GA8 and GA29 , although conversion of GA19 was slow. GA4 was converted to GA 34 but not to GA1 or GA8 . Photoperiod had little effect on any of these metabolic steps. For the following reasons, we suggest that the photoperiod growth response is not mediated primarily through altered GA concentrations: (1) a lack of a rapid photoperiod effect on GA concentrations or metabolism, (2) changes in growth before or independent of changes in GA concentrations and (3) a normal photoperiod effect on growth in petioles with artificially lowered GA content. 
