Fomesafen herbicide application has become major pollution in the growth and production of crops. Spraying fomesafen on the target crops may drift out to non-target crops. In northeast China, sugar beets are always planted adjacent to soybeans. Salicylic acid (SA) plays an important role in crop growth and alleviating abiotic stress, however, the role of SA in relieving fomesafen stress in sugar beet growth has rarely been investigated. Therefore, a pot study was conducted to elucidate the effects of different concentrations (0.025, 0.25, 0.5, 1, 5, and 10 mM) of SA on morphological parameters, photosynthetic performance, and antioxidant defense system in sugar beet seedlings under fomesafen (22.5 g a.i. ha^-1) stress. The results showed that fomesafen stress inhibited the growth of sugar beet seedlings, and photosynthetic performance, while increased membrane lipid peroxidation and oxidative stress. However, exogenous SA alleviated the fomesafen stress and increased plant height, biomass, photosynthetic pigment contents, net photosynthetic rate (Pn), and photochemical efficiency of PSⅡ (Fv/Fm) in sugar beet leaves. Meanwhile, exogenous SA maintained the cell membrane integrity by reducing the content of malondialdehyde (MDA) and electrolyte permeability and regulating the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and polyphenol (PPO). Therefore, it is concluded that exogenous SA ameliorated the adverse effects of fomesafen on the growth of sugar beet seedlings, with a pronounced effect at 1 mM SA. The present study results may have useful implications in managing other plants that are poisoned by herbicides.

Fomesafen is the most widely used herbicide in the soybean field. However, there are urgent practical challenges with the long-term persistence of fomesafen in soil and its effects on the subsequent crops in agricultural production. Therefore, pot experiments were conducted to study the effects of fomesafen residues (0-0.05 mg kg^-1) on growth, photosynthetic characteristics, and the antioxidant defense system of sugar beet seedlings. The results showed that with the increase of fomesafen residues, the phytotoxicity index increased, while the plant height, leaf area, root length, root volume, and dry weight of sugar beet decreased. Photosynthetic pigment content, net photosynthetic rate (Pn), maximum photosynthetic efficiency (Fv/Fm), and actual photosynthetic efficiency (Y(II)) declined with a dose-dependent manner of fomesafen, but the intercellular CO₂ concentration (Ci) and non-photochemical quenching coefficient (NPQ) increased under fomesafen. On the other hand, the residues of fomesafen increased the content of malondialdehyde (MDA) and membrane permeability by aggravating oxidative stress and triggering the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO). In addition, sugar beet seedlings were significantly sensitive to fomesafen as the concentration of fomesafen in the soil was up to 0.025 mg kg^-1. In conclusion, the present study showed that fomesafen residues in the soil could affect the morphophysiology and photosynthetic performance of sugar beet. This study is beneficial for understanding the effects of the herbicide fomesafen residues on non-target crops.

This sugar beet acts as a soil remediator in areas where there are high levels of boron (B) in the soil, since it has a high requirement of boron (B) for growth, and has strong resistance to high B levels. Although B toxicity in different plants has been widely researched, little is known about the response of photosystem II (PSII) activity in sugar beet leaves to B toxicity at present. To clarify the growth and photosynthetic physiological response of sugar beet to B toxicity, the effects of different concentrations of H₃BO₃ (0.05, 1.5, 2.5,3.5 mM) on the growth, photosynthetic characteristics and antioxidant defense system of sugar beet seedlings were investigated by hydroponic experiments. In the present study, high B stress inhibited the growth of sugar beet and significantly decreased the biomass of the plants. There was a remarkable increase in the accumulation of B in the shoots, which affected photosynthesis and decreased the photosynthetic pigments. As B toxicity increased, leaf PSII activities and maximum photochemical efficiency of PSII (F_v/F_m) showed a tendency to decrease; at the same time, the photosynthetic performance index based on absorbed light energy (PI_ABS) decreased as well. Meanwhile, the energy allocation parameters of the PSII reaction center were changed, the light energy utilization capacity and the energy used for electron transfer were reduced and the thermal dissipation was increased at the same time. Furthermore, B toxicity decreased catalase (CAT) activity, increased peroxidase (POD) and superoxide dismutase (SOD) activities, and increased malondialdehyde (MDA) accumulation. According to the results obtained in this study, high B concentrations reduced the rate of photosynthesis and fluorescence, thus weakened antioxidant defense systems, and therefore inhibited the growth of sugar beet plants. Thus, in high B areas, sugar beet possesses excellent tolerance to high B levels and has a high B translocation capacity, so it can be used as a phytoremediation tool. This study provides a basis for the feasibility of sugar beet resistant to high B environments.