不同浓度四环素和土霉素对生菜生长的影响及生态毒性

Effects of different concentrations of tetracycline and oxytetracycline on the growth and ecotoxicity in lettuce

四环素类抗生素(TCs)是目前我国应用广泛、用量最大的一类抗生素,畜禽粪便和土壤中存在TCs残留,影响蔬菜作物的生长发育. TCs因水溶性较高更容易被植物转运和积累,植物对TCs耐受性机理研究仍不足.为更全面探究土壤TCs对蔬菜的毒性作用,研究不同浓度四环素(TC)和土霉素(OTC)分别对生菜的抗生素残留、生长特征及抗氧化酶系统的影响.结果显示,在0(对照)、2、10、50、250 mg/kg 5个施用水平下,生菜叶片抗生素含量逐渐增加,且土霉素含量始终大于四环素含量.与对照相比,抗生素浓度在50 mg/kg以上时对生菜生长具有显著抑制作用,其中,株高、根长、地上部和地下部鲜重与叶片TC残留量具显著负相关.生菜叶片的脯氨酸含量随浓度增加呈先增加后降低的趋势,在10 mg/kg时达到最大.并且低浓度(2 mg/kg)促进抗氧化酶基因SOD、POD21和CAT的表达,高浓度抗生素(50、250 mg/kg)对其产生抑制作用,10 mg/kg的抗生素处理对SOD、POD21和CAT基因表达的影响在抗生素种类上存在差异.本研究表明抗生素浓度超过50 mg/kg对生菜生长产生抑制作用,脯氨酸和抗氧化酶SOD、POD、CAT的转录水平及其酶活性能快速响应抗生素胁迫,可作为生菜对抗生素抗性的辅助评价指标.(图8表3参19)

Tetracycline(TC) antibiotics are the most widely used antibiotics in China. TC antibiotic residues are present in livestock manure and soil, which affect the growth and development of vegetable crops. TCs are easily transported and accumulated by plants because of their high water solubility. However, the mechanism underlying plant tolerance to TC antibiotics remains unclear. To comprehensively explore the toxic effects of soil TC on vegetables, the contents of antibiotics, growth index, proline content, and gene expression of antioxidant enzymes(SOD, POD, and CAT) were studied in lettuce leaves after treatment with TC and oxytetracycline(OTC).Treatments were applied by pouring the antibiotic under the substrate at the time of cultivation. Under application levels of 0(control), 2, 10, 50, and 250 mg/kg, the antibiotic content of lettuce leaves gradually increased,and the content of OTC was greater than that of TC. Compared to the control, lettuce growth was significantly inhibited when the antibiotic concentration was 50 mg/kg. Among them, plant height, root length, and aboveground and underground fresh weight were significantly negatively correlated with the measurement of TC residues in leaves. The proline content of lettuce leaves first increased and then decreased with an increase in TC concentration, reaching a maximum at 10 mg/kg. In addition, low concentrations(2 mg/kg) promoted the expression of antioxidant enzyme genes SOD, POD21, and CAT, whereas high concentrations of antibiotics(50and 250 mg/kg) inhibited them. The effects of antibiotic treatment(10 mg/kg) on the expression of SOD, POD21,and CAT differed depending on the type of antibiotic. The above results showed that antibiotic concentrations of 50 mg/kg and above inhibited lettuce growth. Proline content, antioxidant enzyme transcription level, and enzyme activity can quickly respond to antibiotic stress, which could be used as an auxiliary evaluation index of antibiotic resistance in lettuce.