土壤外源甲基叔丁基醚胁迫对玉米幼苗生理生化特性的影响

Effects of MTBE stress on physiological-biochemical characteristics in maize seedling

以大宗作物玉米作为试验对象，通过盆栽试验，研究外源甲基叔丁基醚（MTBE）污染胁迫对玉米幼苗生长及几项生理生化指标的影响。结果表明，在0～500mg·kg^-1范围内，玉米幼苗未产生明显的毒害作用。土壤中MTBE浓度〈5mg·kg^-1，玉米幼苗生长未受影响，在高浓度下（50mg·kg^-1和500mg·kg^-1），生长受到不同程度的抑制，株高降低36．4％，根干重减少16．6％～34％，地上部分干重减少了46％-59％，根冠比增加，并达到显著水平。叶绿素总量、叶绿素a、叶绿素卜和类胡萝卜素含量均呈现下降的趋势，叶绿素a／b值由对照组2．92降低到1．98，达到极显著水平（P〈0．01）。低浓度MTBE污染对玉米幼苗生理生化指标没有明显的抑制作用，随着土壤MTBE污染程度的加剧，玉米幼苗细胞膜透性逐渐增加，SOD活性逐渐提高。玉米幼苗MDA、CAT和POD对MTBE胁迫的响应表现出相似的规律，累积峰值出现在50mg·kg^-1 MTBE污染水平下。低浓度MTBE污染，叶片中MDA、CAT和POD没有明显变化，高浓度的MTBE污染则诱导酶活性升高，表明氧化胁迫程度增加。但当MTBE浓度达到500mg·kg^-1，由于过多的H2O2或MTBE积累引起MDA、CAT和POD酶活性下降。综合生物量变化及抗氧化酶的响应结果，认为玉米幼苗具有一定的抵御MTBE伤害的应答防御系统。

The effects of MTBE stress on physiological-biochemical characteristics in maize seedlings were investigated by pot experiments.The results showed that maize seedlings exhibited no obvious toxicity symptoms in the whole dose range, and the growth of maize seedlings was not affected by 5 mg·kg^-1 K MTBE. With the increasing of MTBE concentrations in soil, the inhibition of maize growth and chlorophyll concentrations in maize leaves was observed to some extends. Under 50 mg·kg^-1 and 500 mg·kg^-1 MTBE stress, plant height decreased 36.4%, dry weight of shoots and root length of maize seedlings decreased respectively 59% and 34%, and the ratio of root to crown （dry weight） tended to increase, the total chlorophyll, chlorophyll a, chlorophyll b and carotenoid were lower than those of the control, and the ratio of chlorophyll a/b decreased remarkably. Low concentration of MTBE had little inhibition on some physiological and biochemical characteristics of maize seedlings. As the MTBE content increased, the plasma membrane＇ s permeability of maize seedlings and the activities of SOD and the content of MDA increased gradually. The content of MDA and the activities of CAT and POD in leaves reached a peak at treatment 50 mg-kgl then come down gradually with the concentrations of MTBE increasing continuously. The activities of CAT and POD in the leaves did not change much at low MTBE concentrations （less than 5 mg·kg^-1）, but fluctuated drastically at high MTBE concentrations, on the contrary, which inhibited significantly when maize was grown in solutions with 500 mg·kg^-1 MTBE, as a result of the content and accumulation of H2O2 or MTBE in maize seedling increased. Based on the results of this study, indicating that maize seedling had an excellent response way against MTBE damage.