Does drought stress intensify the allelopathy of invasive woody species Rhus typhina L.?

Key MessageDrought stress intensified the allelopathy of Rhus typhina L. and Sapindus mukorossi Gaerten, and drought stress reinforced the allelopathy of S. mukorossi more significantly than R. typhina. The allelopathy mediated by the allelochemicals may be one of the vital issues driving the invasion process of invasive plants. Indigenous plants may also generate obvious allelopathy via the released secondary metabolites on the adjacent plants to occupy more habitats. However, the differences in the allelopathy of invasive plants and indigenous plants may be changed under increasing drought stress. Thus, this study aimed to estimate the differences in the allelopathy (using aqueous leaf extracts) between invasive woody species (Rhus typhina L.) and indigenous woody species (Sapindus mukorossi Gaerten) on seed germination and seedling growth performance of the horticultural plant Lactuca sativa L. (hypersensitive to allelochemicals) under drought stress. R. typhina and S. mukorossi created obvious allelopathy on seed germination and seedling growth performance of L. sativa, and the allelopathy of R. typhina was notably stronger (55.03% higher) than that of S. mukorossi. Drought stress intensified the allelopathy of R. typhina (14.59% higher) and S. mukorossi (54.17% higher). However, drought stress reinforced the allelopathy of S. mukorossi more significantly (67.86% higher) than R. typhina. Thus, drought stress can accelerate the invasion process of invasive plants as well as the expansion process of indigenous plants via the reinforced allelopathy, but the invasion process mediated by the allelopathy of invasive plants may be relatively weakened by the stronger reinforced allelopathy of indigenous plants to some extent under drought stress.

Automated summary

Drought stress intensifies the allelopathy of Rhus typhina and Sapindus mukorossi, with the latter experiencing a more significant increase in allelopathy. This study aimed to assess the differences in allelopathy between invasive and indigenous woody species, and their effects on the seed germination and seedling growth of Lactuca sativa under drought stress. The results showed that both Rhus typhina and Sapindus mukorossi exhibited strong allelopathy, with Rhus typhina being notably stronger. Drought stress intensified the allelopathy of both species, but had a more significant effect on Sapindus mukorossi. This suggests that drought stress can accelerate the invasion and expansion processes of plants, but the stronger allelopathy of indigenous plants may weaken the invasion process to some extent under drought stress.