连作马铃薯不同生育期根系分泌物的成分检测及其自毒效应

Identification and autotoxicity of root exudates of continuous cropping potato at different growth stages

为探讨马铃薯连作障碍的可能机理,在大田条件下,以轮作为对照(CK),收集连作5年(CP5)马铃薯植株在不同生育期的根系分泌物,采用GC-MS对根系分泌物的主要成分进行了鉴定,并通过生物检测验证了根系分泌物的自毒效应。结果表明:CK和CP5处理的马铃薯在不同生育期的根系分泌物均鉴定出糖类、酸类、胺类、脂类、醇类和嘧啶类等成分,以糖类和酸类物质居多;CP5处理根系分泌物的成分较CK复杂,酸类物质含量有升高的趋势。连作改变了马铃薯根系分泌物的化学组成和含量:CP5处理在苗期、现蕾期和开花期的根系分泌物中均鉴定出邻苯二甲酸二丁酯,相对含量分别为0.16%、0.21%和0.24%,CK处理未检测到;CP5处理在苗期、现蕾期和开花期的根系分泌物中均鉴定出棕榈酸,相对含量分别为0.34%、1.12%和0.47%,CK处理仅在现蕾期和开花期鉴定出棕榈酸的存在,但相对含量仅为0.56%和0.24%。生物检测试验结果表明,棕榈酸和邻苯二甲酸二丁酯显著抑制了马铃薯生长,1 mmol·L-1棕榈酸和邻苯二甲酸二丁酯对马铃薯生长的抑制作用远远大于0.5 mmol·L-1的抑制作用。棕榈酸和邻苯二甲酸二丁酯是马铃薯根系分泌的自毒物质,但二者未表现出物质的叠加效应。现蕾期马铃薯根系分泌物所含的物质最多,是马铃薯根系分泌物收集的适宜时期。

Potato root exudates were collected from two treatments（CK： potato rotation with other crops; CP5： continuous potato cropping for five years） under field conditions to explore the possible obstacle mechanisms of continuous cropping of potato. The root exudates were collected at three growth stages — seedling, squaring and florescence stages. The chemical composition of the root exudates were determined by the GC-MS method and the autotoxicity of the exudates to potato plants tested in a pot experiment. The results showed that the main components of potato root exudates in both CK and CP5 treatments included glucides, organic acids, amines, alcohols, esters and pyrimidines, with glucides and organic acids as the dominant components. Also while the chemical composition of root exudates of CP5 was much more complex than that of CK, the content of organic acids in CP5 was significantly higher than in CK. The compound, dibutyl phthalate（DP）, existed only in root exudates of CP5, with relative contents of 0.16%, 0.21% and 0.24% respectively at seedling, squaring and florescence stages. Root exudates of CP5 also was tested positive for the compound palmitic acid（PA）, with relative contents of 0.34%, 1.12% and 0.47% respectively at seedling, squaring and florescence stages. Although PA was detected in CK treatment, it only appeared at squaring and florescence stages in respective concentration of 0.56% and 0.24%. Biological analyses showed that PA and DP significantly inhibited potato growth. The inhibiting effect of PA or DP of 1 mmol·L^-1 was far exceeded that of 0.5 mmol·L^-1 concentration. Continuous potato cropping changed the composition of potato root exudates, and PA and DP were autotoxins of potato root exudates, though with no superimposition effects. Potato root secreted much more root exudates at squaring stage, which period was suitable for collection of potato root exudates.