To assess the potential for enhancing lodging resistance in legumes through the application of plant growth regulators (PGR) and changes in stem structure, the stem morphological and anatomical characteristics, as well as the chemical composition, of Vicia sativa and Vicia pannonica were analysed before and after treatment with different doses of PGR trinexapac-ethyl. The aim was to identify stem morpho-anatomical components that impact lodging resistance, quantify the dose-dependent effect of the chosen PGR on the Vicia stem and examine if stem lodging resistance could be improved through PGR application, as well as determine if some of the stem characteristics could be used as markers for lodging resistance prediction.

Although in both species lodging index increased (14–126%), suggesting improved resistance to lodging, and stem height decreased (12–38%) upon PGR application, the impact on V. sativa was more pronounced. The findings indicate that, apart from stem height, none of the examined morpho-anatomical characteristics showed a high and significant correlation with the lodging index. Therefore, none of these characteristics can be used as a marker for predicting lodging resistance. Increased proportion of cortex, cylinder parenchyma and collenchyma, along with reduced central cavity, might contribute to a greater lodging resistance in V. sativa. PGR decreased the amount of lignin, cellulose and hemicellulose. These results encourage the use of PGR for lodging resistance improvement in vetches, through the reduction of stem height, since this modification did not adversely affect the stem structure or grain yield.