氮沉降背景下土壤微生物对入侵植物乌桕叶绿素荧光特征的影响

Abstract

植物入侵会造成入侵地生态系统功能和稳定性的破坏。与原产地种源相比，入侵种源植物在生理学特性方面有所不同，使其在资源利用和抵抗环境胁迫具有较强的竞争优势。叶绿素荧光特性与植物光合作用效率密切相关，对植物生长具有重要作用。氮沉降加剧是全球变化的一个重要因子，土壤微生物对植物吸收利用土壤养分至关重要。通过施用细菌抑制剂（链霉素）和真菌抑制剂（扑海因）选择性抑制的土壤微生物活性，开展乌桕盆栽实验，在模拟氮沉降背景下，研究不同微生物群落如何影响入侵乌桕叶绿素荧光特性，有助于理解入侵植物的进化特征和入侵机制，为有效防控入侵植物并降低其对生态系统危害提供理论依据。以原产地地和入侵地两个种源乌桕（Triadica sebifera）为研究对象，在氮沉降条件下，通过调控土壤细菌和真菌，探讨两个种源乌桕叶绿素荧光参数差异。结果显示：氮沉降显著增加乌桕相对叶绿素含量（SPAD）、光系统II的最大量子产率（F_v/F_m）、非光化学猝灭（NPQ）和半饱和光强（I_k）。入侵种源乌桕比原产地具有较低SPAD。氮沉降与细菌抑制剂共同作用显著增强了F_v/F_m、NPQ和I_k，显著减弱了光能利用率（α）和SPAD。细菌抑制剂减缓了本地种源乌桕α，真菌抑制剂促进本地种源乌桕I_k，抑制入侵种源乌桕I_k，细菌和真菌抑制剂可显著降低原产地乌桕α。氮沉降与生物抑制剂可显著作用于乌桕叶片SPAD。氮沉降、土壤微生物和不同乌桕种源可共同作用于光系统Ⅱ实际光合量子产率Y（Ⅱ），α和潜在最大相对电子传递速率（ETR_max）。因此，氮沉降与生物抑制剂对乌桕叶绿素荧光特性具有协同作用，入侵种源乌桕对土壤微生物控制的响应不明显，在微生物控制条件下依然具有较强的适应能力，因而具有较强的入侵能力。;Plant invasions cause damage to both function and stability of invaded ecosystems. Compared with plants from the native origin, the invasive origin plants are different in physiological characteristics, which make them stronger in competitive ability in resource utilization and environmental stress resistance. The chlorophyll fluorescence characteristics are closely related to photosynthetic efficiency and play important roles in plant growth and expansion. Additionally, increased nitrogen deposition is an important factor of global change, while soil microorganisms are crucial for plants to absorb and utilize soil nutrients. By application of soil microbial inhibitors to control the activities of bacterial communities (by streptomycin) or fungi communities (by iprodione), study on invasive plant Triadica sebifera was carried out using pot experiment to understand how different microbial communities affect the chlorophyll fluorescence characteristics of T. sebifera from both the native and invasive origins under the background of simulated nitrogen deposition. The study will be helpful in understanding the evolutionary characteristics and invasion mechanism of invasive plants, and provide a theoretical basis for effectively preventing and controlling invasive plants, reducing their damage to the invaded ecosystems. The study was performed using a nested design, Triadica sebifera was used as the research object with two origins, including native and invasive origins. Under the condition of nitrogen deposition, the difference in the chlorophyll fluorescence parameters of the two origins of T. sebifera were investigated by regulating soil bacteria and fungus. Results showed that, nitrogen deposition significantly increased the relative chlorophyll content (SPAD), the maximum quantum yield of photosystem II (F_v/F_m), non-photochemical quenching (NPQ), half-satiety and light intensity (I_K) of T. sebifera. The invasive origin of T. sebifera had lower SPAD than the native origin. The combination of nitrogen deposition and bacterial inhibitor significantly enhanced F_v/F_m, NPQ and I_K, and significantly reduced light energy utilization (α) and the SPAD. The bacterial inhibitors decreased the native T. sebifera α. Fungi inhibitors promoted I_K of the native T. sebifera and inhibited I_k of the invasive T. sebifera. Nitrogen deposition, biological inhibitor and T. sebifera origin can act together on the PSII actual photosynthetic quantum yield Y(Ⅱ), α and potential maximum relative electron transfer rate (ETR_max). Therefore, nitrogen deposition and fungi inhibitors had a synergistic effect on the chlorophyll fluorescence characteristics of T. sebifera. The invasive origin of T. sebifera had no obvious response to the control of soil microorganisms, so it still had a strong adaptability under the control of microorganisms, and thereby had strong invasion ability.