Abstract
Gibberellin (GA) levels in leaf sheaths and in elongating leaf bases of perennial ryegrass (Lolium perenne L. cv. Bravo) were monitored in undefoliated and defoliated plants. Nine C‐13‐hydroxylated GAs (GA8, GA97, GA29, GA1, GA20, GA44, GA19, GA17, GA53) and one C‐13‐non‐hydroxylated GA (GA9) were identified by combined gas chromatography‐mass spectrometry in leaf extracts. The total level of GA8, GA29, GA1, GA20, GA44, GA19 and GA53, determined by selected ion monitoring, was 7 times higher in elongating leaf bases than in mature leaf sheaths. In both leaf tissues, defoliation induced an increase in GA53 level, while GA20 and GA1 levels decreased, suggesting that the GA53→GA44, as well as GA19→GA20, conversions were slowed down. The roles of GA1 in the control of leaf elongation and fructan mobilization following defoliation are discussed.
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