铵态氮和硝态氮对香蕉枯萎病发生的比较研究

Comparative study of ammonium and nitrate on banana wilt disease development

为寻找降低香蕉枯萎病发生的防治措施,通过室内盆栽接种试验,研究了铵态氮(NH4+-N)和硝态氮(NO3--N)对香蕉枯萎病发生及其植株叶绿素含量、气体交换参数、病原菌在植物体内的数量分布和植物钙(Ca)、镁(Mg)、铁(Fe)、钼(Mo)、可溶性糖和木质素含量的效应。结果表明:不接种病原菌的条件下,不同氮素处理对香蕉幼苗生长影响无差异;接菌情况下,与NH4+-N处理相比,NO3--N处理显著降低植株各器官的病原菌数量、发病率和发病严重程度。病原菌侵染后,不同氮素处理下植株光合作用均显著下降:NO3--N处理香蕉苗保持比NH4+-N处理更高的光合速率;病原菌侵染后NH4+-N处理的植株Ca、Mg、Fe和Mo含量相对于侵染前没有显著差异,但NO3--N处理下此4种元素含量均显著升高。病原菌侵染后的植株叶片可溶性糖含量在不同氮素处理中都没有显著变化,但在根系中,NO3--N处理的侵染植株可溶性糖含量显著降低。与此同时,病原菌侵染后,木质素含量在NH4+-N处理植株中变化不显著,但其含量在NO3--N处理侵染后显著上升。综上所述,NO3--N处理可增加植株抗病相关矿质元素的吸收,诱导香蕉苗木质素形成,使其木质化程度增加,从而维持较高的光合作用,保持较高的抗病水平。

In order to find the measure to control the Fusarium wilt disease of banana, effects of ammonium （NH4^＋-A） and nitrate （NO3^- -N） applications were studied on disease index, chlorophyll content, gas exchange parameters, pathogen distribution, concentrations of Ca, Mg, Fe and Mo, soluble carbohydrate content and lignin content of banana seedlings grown with pot experiment and infected by Fusarium oxysporum f. sp. cubense （FOC）. The results showed no difference in growth of banana seedlings between two forms of nitrogen treatment. However, after pathogen inoculation, compared with ammonium treatment, nitrate treatment could significantly reduce the pathogen levels in various plant organs as well as disease incidence and disease severity. Pathogen challenge reduced plant photosynthetic rate under both nitrogen treatment conditions. Nitrate treatment maintained a relative higher photosynthetic rate compared than the ammonium treatment. Nitrate treatment signif- icantly enhanced the contents of Ca, Mg, Fe and Mo in plant after FOC infection. The content of leaf soluble carbohydrate was not affected by either treatment, but the root carbohydrate content was reduced in nitrate treated banana seedlings. Lignin content was relatively stable in ammonium treatment, whereas it increased significantly in nitrate treatment following pathogen infection. It was concluded that the effect of nitrate treatment on enhanced disease resistance of banana plants was probably due to the elevated absorption of resistance-related nutrients which induced the synthesis of lignin and the enhanced lignification therefore maintaining a higher pho- tosynthetic rate and high disease resistance.