Effects of uniconazole or ethephon foliar application on culm mechanical strength and lignin metabolism, and their relationship with lodging resistance in winter wheat

Abstract

Lodging in plants is an important constraint that leads to yield losses and cause problems with mechanical harvesting. This research was aimed at determining the effects of foliar application of uniconazole or ethephon on lignin metabolism, characteristics of second basal internode and their relationship with lodging resistance in winter wheat (Triticum aestivum L.). In separate experiments, uniconazole was sprayed on the foliage at concentrations of 0, 15, 30 and 45 mg L–1, and ethephon at concentrations of 0, 50, 75 and 100 mg L–1 at the four-leaf stage. Foliar application of uniconazole or ethephon significantly reduced the lodging rate by increasing the lignin content and optimising basal-internode characteristics. Lignin content was significantly positively correlated with breaking strength, and negatively correlated with lodging rate, whereby the higher lignin content in the second basal internode significantly improved the lodging resistance and reduced the lodging rate in the wheat crop. Foliar application of uniconazole or ethephon also increased the breaking strength, internode diameter, wall thickness and internode plumpness of the second basal internode; maximum values were obtained with uniconazole at 30 mg L–1 and with ethephon at 75 mg L–1. Grain yield, lignin content and lignin-related enzyme activities of phenylalanine ammonia-lyase, tyrosine ammonia-lyase, cinnamyl alcohol dehydrogenase and peroxidase were all significantly improved with the foliar application of uniconazole or ethephon. These results suggest that lignin content in the second basal internode in wheat was closely related with lodging resistance. Foliar application of uniconazole or ethephon at the four-leaf stage reduced the lodging rate, and the concentration showing the greatest effects was 30 mg L–1 for uniconazole or 75 mg L–1 for ethephon.