Journal of Plant Ecology ›› 2022, Vol. 15 ›› Issue (3): 461-472.DOI: 10.1093/jpe/rtab068

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  • 收稿日期:2020-12-24 修回日期:2021-03-15 接受日期:2021-06-06 出版日期:2022-06-01 发布日期:2022-06-23

Effects of soil nitrogen levels on growth and defense of the native and introduced genotypes of alligator weed

Mu Liu1, Fang Zhou1, Xiaoyun Pan1,2,3, *, Zhijie Zhang4 and Bo Li1   

  1. 1 Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai 200438, China, 2 Research Center for Ecology, College of Science, Tibet University, Lhasa 850000, China, 3 Tibet University—Fudan University Joint Laboratory for Biodiversity and Global Change, Fudan University, Shanghai 200032, China, 4 Ecology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany

    *Corresponding author. E-mail: xypan@fudan.edu.cn
  • Received:2020-12-24 Revised:2021-03-15 Accepted:2021-06-06 Online:2022-06-01 Published:2022-06-23

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摘要： 土壤氮水平对喜旱莲子草原产地和引入地基因型生长和防御的影响
同种植物生长在资源丰富生境中的个体，其防御水平被认为低于生长在资源匮乏生境中的个体。然而，生境的养分水平如何影响植物的诱导抗性和耐受性，以及这种影响在入侵植物的原产地和引入 地种群间是否存在差异，目前均知之甚少。本研究以入侵植物喜旱莲子草(Alternanthera philoxeroides)的原产地阿根廷和引入地美国的基因型为研究对象设计同质园实验，以探究土壤氮水平对植物的生长、组成和诱导性[莲草直胸跳甲(Agasicles hygrophila)取食诱导]化学防御以及耐受性的影响。实验中，我们测定了植物总生物量、伸长速率(生长速率的表征)以及叶片和根系中总碳、总氮和三萜皂苷(化学防御物质)的含量。研究结果显示，植物在低土壤氮水平下表现出较高的组成抗性(植物在低土壤氮水平下的叶片三萜皂苷含量高于其在高土壤氮水平的33%)和耐受性[植物被取食后总生物量下降的程度更低(植物在高土壤氮水平和低土壤氮水平下被取食后总生物量分别下降了24%和15%)]，而在高土壤氮水平下表现出较高的诱导抗性(在高土壤氮水平下的植物被取食后叶片三萜皂苷含量与空白对照的植物相比升高了24%)。植物的组成抗性和耐受性与生长速率存在权衡，但诱导抗性与生长速率存在显著的正相关性。此外，引入地基因型在低土壤氮水平下叶片碳含量显著低于原产地基因型(-6%)，但这种差异在高土壤氮水平下消失。这些结果表明，土壤氮水平 影响植物对不同防御策略的选择偏好，并且在决定引入地基因型的表现时与植食作用存在交互作用。

关键词: 喜旱莲子草(Alternanthera philoxeroides), 莲草直胸跳甲(Agasicles hygrophila), 生长-分化平衡假说, 表型可塑性, 植物-植食者互作关系, 植物入侵

Abstract:

Plants growing in nutrient-rich environment are predicted to be less defended than conspecifics under nutrient limitation. However, less is known about the effects of nutrient levels on tolerance and induced resistance, and whether the effects differ between native and introduced populations of invasive plants. We performed a greenhouse experiment with introduced (the USA) and native (Argentina) genotypes of Alternanthera philoxeroides in order to study the effects of soil nitrogen levels on plant growth, constitutive and herbivore (Agasicles hygrophila)-induced chemical defense, and herbivory tolerance. We measured total biomass, elongation rate (as proxy of growth rate), carbon and nitrogen, and the concentration of triterpenoid saponins (defensive chemicals) in leaves and roots. Constitutive resistance (+33% higher leaf triterpenoid saponins in control treatment at low nitrogen level) and tolerance [less decreased total biomass after herbivory treatment (−24% and −15% for high and low nitrogen levels)] were favored at lower nitrogen level, while induced resistance was favored at higher nitrogen level (+24% increased leaf triterpenoid saponins after herbivory treatment at high nitrogen level). Constitutive resistance and tolerance exhibited trade-offs with growth rate, while induced resistance positively correlated with growth rate. Additionally, the introduced genotypes had −6% lower content of leaf carbon in the presence of herbivores than the native genotypes at low nitrogen level, but such difference was absent at high nitrogen level. Our results indicate that soil nitrogen levels influence the preference of different defensive strategies of plant, and interweave with herbivory to determine the performance of introduced genotypes.

Key words: Alternanthera philoxeroides, Agasicles hygrophila, growth–differentiation balance hypothesis, phenotypic plasticity, plant–herbivore interactions, plant invasion

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