UVRESISTANCE LOCUS 8 signalling enhances photosynthetic resilience to herbicide‐induced damage in Arabidopsis thaliana

Summary Perception of low irradiance ultraviolet B (UV‐B) light (280–315 nm) by the UV RESISTANCE LOCUS 8 (UVR8) photoreceptor initiates signalling pathways that enhance plant defences to UV‐B damage, mitigating the effects of higher photon irradiances. We therefore questioned whether UVR8 signalling could also prime plants against herbicide‐induced damage, promoting postspray survival. We assessed the effects of a 2 d, low irradiance UV‐B pretreatment on the photosynthetic resilience and survival of Arabidopsis thaliana plants treated with herbicides promoting photosynthetic disruption and oxidative stress. UV‐B acclimation increased leaf carotenoid production, antioxidant activity and nonphotochemical quenching (NPQ) and delayed herbicide‐induced reductions in electron transport rate (ETR), facilitating postspray regrowth and enhancing plant survival. In the absence of UV‐B, this protection declined within 4 d, suggesting that it is unlikely to result from structural modifications. UV‐B‐mediated enhancement of photosynthetic resilience was abolished in the uvr8‐6 mutant and increased in the UV‐B hyper‐responsive repressor of UV‐B photomorphogenesis1/2 (rup1rup2) mutant, highlighting the involvement of UVR8 signalling. UV‐B filtering during daylight acclimation also increased herbicide efficacy in Chenopodium, suggesting similar responses in agricultural weeds. UV‐B‐induced photoprotection enhances the resilience of plant photosystems to herbicide damage, providing a key target for increasing product efficacy and reducing usage.