Abstract
Radix Isatidis (Isatis indigotica Fort.) is one of the most important traditional Chinese medicine plants. However, there is no suitable herbicide used for weed control in Radix Isatidis field during postemergence stage. To explore the safety of sulfonylurea herbicide nicosulfuron on Radix Isatidis (Isatis indigotica Fort.) seedlings and the photosynthetic physiological response of the plant to the herbicide, biological mass, leaf area, photosynthetic pigment content, photosynthetic rate, chlorophyll fluorescence characteristics, and P700 parameters of Radix Isatidis seedlings were analyzed 10 d after nicosulfuron treatment at 5th leaf stage in this greenhouse research. The results showed that biological mass, total chlorophyll, chlorophyll a, and carotenoids content, photosynthetic rate, stomatal conductance, PS II maximum quantum yield, PS II effective quantum yield, PS II electron transport rate, photochemical quenching, maximal P700 change, photochemical quantum yield of PS I, and PS I electron transport rate decreased with increasing herbicide concentrations, whereas initial fluorescence, quantum yield of non-regulated energy dissipation in PS II and quantum yield of non-photochemical energy dissipation due to acceptor side limitation in PS I increased. It suggests that nicosulfuron ≥1 mg L−1 causes the damage of chloroplast, PS II and PS I structure. Electron transport limitations in PS I receptor side, and blocked dark reaction process may be the main cause of the significantly inhibited growth and decreased photosynthetic rate of Radix Isatidis seedlings.
Highlights
As one of the most important traditional Chinese medicine plants, Radix Isatidis (Isatis indigotica Fort.), one kind of cruciferous plants, is extensively cultivated in China
The safety of herbicides on plants may be represented through agronomic traits and physiological indexes [1,25,26]
Nicosulfuron was unsafe to Radix Isatidis seedlings being reflected by reduced chlorophyll content and Photosynthetic rate (Pn)
Summary
As one of the most important traditional Chinese medicine plants, Radix Isatidis (Isatis indigotica Fort.), one kind of cruciferous plants, is extensively cultivated in China. Compared with conventional manual control of weeds, chemical control is more effective, yet there is no suitable herbicide used for weed control in Radix Isatidis field during postemergence stage [1]. Nicosulfuron (2-((4,6-dimethoxypyrimidin-2-ylcarbamoyl)sulfamoyl)-N, N-dimethylnicotinamide) belongs to the acetyl lactic acid synthase (ALS) inhibitor, and can effectively control many perennial and annual grasses as well as certain broadleaf weeds [2,3]. It is reported that nicosulfuron can effectively control large crabgrass (Digitaria sanguinalis) cornfield, goosegrass (Eleusine indica), spiny amaranth (Amaranthus spinosus L), amaranthus blitum (Amaranthus ascendens Loisel.), speargrass (Imperata cylindrica), and purslane (Portulaca oleracea) in maize field [4]. The leaves of sensitive maize variety may show symptoms of chlorosis and shrinking 7 d after applying nicosulfuron [7]. The resistance of plant to nicosulfuron depends on its metabolic rate, sensitivity to ALS, and nicosulfuron dosage [9,10,11]
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