Legume plants may facilitate Zanthoxylum bungeanum tolerance to extreme rainfall

A complete randomized design was implemented with two watering regimes (extreme rainfall and control) and three different plant combinations (Zanthoxylum bungeanum, Z. bungeanum + Capsicum annum, Z. bungeanum + Glycine max) in order to assess the morphological and physio-biochemical responses of focal and neighbor plants. The results indicated that, extreme rainfall had significantly negative impacts on Z. bungeanum in three intercropping systems. However, intercropping with G. max improved the transpiration rate (T_r) and stomatal conductance (G_s), raised leaf relative water content (LRWC), increased chlorophyll a (Chl a) and carotenoid (Car) content, and enhanced the superoxide dismutase activity (SOD) of Z. bungeanum. After recovery, the Z. bungeanum + G. max mixed culture significantly increased soil NO₃^--N, improved the intercellular carbon dioxide concentration (C_i) and T_r, upregulated soluble sugar and proline, and enhanced hydrogen peroxidase activity (CAT). Moreover, the higher root biomass of G. max provided much more nitrogen for Z. bungeanum via the return of organic matter. However, intercropping with C. annum significantly increased active oxygen (ROS). Compared with neighboring species, in intercropping systems, G. max could have improved the tolerance of the focal species Z. bungeanum in response to extreme rainfall and its recovery after extreme rainfall.