施氮水平影响蚯蚓介导的番茄生长及抗虫性

Nitrogen levels modify earthworm-mediated tomato growth and resistance to pests

过量施用氮肥不仅导致严重的生态环境问题,还会限制土壤生物驱动的生态系统服务功能。蚯蚓的取食和掘穴等活动可以促进土壤肥力和植物生长,进而影响植物与病虫害的关系。了解氮肥与害虫作用下蚯蚓对植物抗虫性的影响,有助于揭示土壤动物的生态功能调控机制。采用蚯蚓(威廉腔环蚓Metaphireguillelmi)、西花蓟马(Frankliniellaoccidentalis)和氮肥用量的三因子完全交互设计,利用番茄(Lycopersiconesculentum)盆栽实验探索了不同氮水平下蚯蚓对番茄生长及对植食者抗性的影响。结果表明,在低氮条件下蚯蚓显著降低了番茄茎叶干生物量、根系干生物量及茎叶可溶性糖含量,而茎叶的茉莉酸和水杨酸含量分别是无蚯蚓对照的6倍和3倍,且伴随着西花蓟马数量下降了58%。在高氮水平时,蚯蚓未影响番茄茎叶茉莉酸、茎叶水杨酸含量及西花蓟马数量。蚯蚓介导的番茄营养物质(茎叶可溶性糖和茎叶全氮)和防御信号物质(茎叶茉莉酸和茎叶水杨酸)含量分别与西花蓟马数量呈显著的正相关和负相关。总之,氮肥施用改变的土壤氮有效性通过改变植物资源和防御物质含量转变了蚯蚓介导的植物抗虫性响应;全面了解土壤生物对植物生长的影响需要综合考虑土壤管理–土壤动物–植物病原物三者之间的关系。

Excessive chemical nitrogen (N) fertilizer application causes serious environmental problems and affects the ecosystem services that depend on soil biota. Earthworms improve soil fertility and plant productivity via activities such as feeding,burrowing and casting,and alter the relationships between crop plants and pests by modifying plant primary and secondary productivity. In order to mechanistically understand the functional roles of soil fauna in ecosystem services,a pot experiment using tomatoes (Lycopersicon esculentum) was conducted in a greenhouse. The study used a complete factorial design that manipulated earthworm (Metaphire guillelmi) abundance,western flower thrips (Frankliniella occidentalis) and N input. Results showed that under low N-input conditions,earthworms significantly reduced shoot and root biomass and shoot soluble sugar content,and increased shoot jasmonic acid content (by 6 times) and shoot salicylic acid content (by 3 times),compared to treatments without earthworms. This was accompanied by the decrease of thrips abundance by 58%,indicating a remarkable suppression of aboveground pests by earthworms. However,under high N-input conditions,earthworm presence did not affect the contents of shoot jasmonic acid or shoot salicylic acid or thrips abundance by the end of the experimental period (45 days). The earthworm-mediated responses of plant nutrition (shoot soluble sugar and shoot total nitrogen) was significantly positively correlated with thrips abundance,whereas defense (shoot jasmonic and salicylic acid) was significantly negatively correlated. Changes to soil N availability due to N fertilizer input can shift the direction of earthworm-mediated plant resistance against herbivores by altering plant resource acquisition and secondary defense. Effects of earthworms on plant growth and resistance depend on soil management practices such as N fertilizer application. A comprehensive understanding of the roles of soil biota in mediating plant growth requires knowledge of the multifaceted relationships among soil management,soil fauna,and plant pathogens.