Effects of mixtalol and paclobutrazol on photosynthesis and yield of rape (Brassica napus)

Photosynthetic and yield effects of paclobutrazol and mixtalol sprayed, respectively, on rape at the three-leaf stage and shoot or anthesis stages were examined. They significantly increased chlorophyll content and photosynthetic rates, prolonged leaf longevity, and increased green pod area. Paclobutrazol-treated plants were shorter, more branched, and produced more seeds. Foliar sprays of mixtalol increased podding percentage, pods per plant, and seeds per pod. A high seed yield of 1809.0 kg/ha was obtained with mixtalol sprayed at anthesis, while significant yields were also achieved with treatments of mixtalol at the shoot stage and paclobutrazol at the three-leaf stage. The photosynthetic and yield effects of mixtalol or paclobutrazol were reduced when both growth regulators were applied together, and this led to yield reductions. No adverse effects from mixtalol or paclobutrazol were observed on seed oil content, erucic acid, and glucosinolate content. The total rape oil production with mixtalol sprayed at anthesis and shoot stages and paclobutrazol at the three-leaf stage increased significantly by 20.9%, 14.4%, and 13.4%, respectively, over the controls.