Effect of neonicotinoid dinotefuran on root exudates of Brassica rapa var. chinensis

Root exudates are released by plant roots and are important carrier substances for material exchange and information transmission among plants and the rhizosphere. In the present study, the effect of dinotefuran on root exudates of Chinese cabbage (Brassica rapa var. chinensis) was investigated. The physiological activities revealed that dinotefuran uptake caused oxidative stress in vegetable tissues even at low dinotefuran exposure levels. The metabolic profile of plant root exudates acquired by LC-QTOF/MS was clearly changed by dinotefuran, where the numbers of both up- and down-regulated MS peaks increased with increasing dinotefuran concentration. Under dinotefuran stress, some osmotic adjustment substances (proline and betaine) and defence-related metabolites (spermidine, phenylalanine and some phenolic acids) were significantly upregulated, which may help plants adapt to adverse environmental conditions. Specifically, the contents of some phenylalanine-derived secondary metabolites increased with increasing dinotefuran concentration, which may increase the external detoxification ability of plants. Moreover, respiration metabolism was significantly affected, where some intermediates in the TCA cycle (succinic acid and malic acid) were upregulated with low-level dinotefuran exposure; however, anaerobic respiration products (lactic acid and 3-phenyllactic acid) were accumulated at high exposure levels. In addition, the release of glucosinolates was significantly inhibited in both dinotefuran treatment groups.