Interaction of gibberellic acid and photoperiod on leaf sheath elongation in normal and gibberellin‐insensitive genotype of wheat

Effect of gibberellic acid (GA3) on leaf sheath elongation in a normal (cv. Møystad) and a gibberellin(GA)‐insensitive (cv. Siete Cerros) genotype of wheat (Triticum aestivum L.) were studied at 18 and 12°C under short (SD, 12 h) or long (LD, 24 h) photoperiod. Leaf sheath length in cv. Møystad was signficantly increased by exogenous GA3 both under SD and LD. LD alone stimulated leaf sheath elongation and the combined effect of LD and GA3 was additive, and there was no statistically signficant interaction between photoperiod and GA3 concentrations. Leaf sheath length in cv. Siete Cerros was not significantly affected by GA3 under any conditions. However, there was a highly significant stimulation of leaf sheath elongation by LD in cv. Siete Cerros as well. These results indicate that stimulation of elongation growth in wheat leaves by LD is not mediated by gibberellin.