Hormonal and Gene Regulation of Leaf and Root Elongation in Tall Fescue.

The objective of this study was to investigate how gibberellin (GA) and a GA inhibitor (trinexapac-ethyl, TE) may regulation leaf elongation at cellular and molecular levels. A tall fescue cultivar, ‘K-31’, were exogenously treated with GA₃ and TE. Compared with the untreated plants, leaf elongation rate of GA_- treated plants was 1.45-fold greater while leaf elongation rate treated with TE decreased by 25% compared to the untreated control.  The epidermal cells in GA-treated leaves were significantly elongated and the length of cells was as 2.12-fold long as the untreated control. TE reduced the length of epidermal cells by 11%. The expression of genes controlling cell wall extensibility was evaluated by qPCR. Three α-expansins and two β-expansins and a xyloglucan endotransglucosylase (XET) gene were regulated by GA and TE, which were up-regulated by GA and down-regulated by TE. The results suggested that GA may control leaf elongation in tall fescue by regulating expansin and xyloglucan endotransglucosylase.