植物地下觅养性状对土壤富磷斑块塑性响应的研究进展

Research Progress on the Plasticity Responses of Plant Below-Ground Foraging Traits to Soil Phosphorus-Rich Patches

磷是影响植物生长的关键养分元素之一,地下细根觅养塑性是植物提高土壤磷吸收的重要方式。在自然环境条件下,土壤养分具有异质性或斑块状分布特点,特别是相对固定的养分(如磷)。植物如何调整地下觅养性状对养分斑块的塑性响应尚不清楚,特定细根性状预测地下觅养性状塑性响应更具有较大不确定性。本研究总结植物地下觅养塑性的影响因素,阐述细根(形态、构型、增殖、化学、生理)和菌根真菌性状对富磷斑块的塑性响应,从真菌侵染方式、根系形态结构、养分获取策略等方面分析地下觅养性状及其塑性响应在丛枝菌根和外生菌根树种间的差异。基于地下觅养的碳成本假设,指出细根形态塑性和生理塑性在许多情况下是资源竞争的结果。真菌菌丝的增殖塑性更能提高植物养分获取效率,但当根系和菌根真菌均存在于养分斑块时,根系增殖比真菌反应更敏感。本研究还探讨细根性状对地下觅养塑性的预测,指出细根直径是地下觅养性状变化的重要预测指标。围绕当前植物地下觅养塑性研究存在的不足,从地下觅养塑性框架、地下觅养机制、细根性状对植物养分获取塑性的预测、细根觅养塑性与防御塑性之间的关系等方面提出今后的研究方向,深入理解植物地下磷养分获取策略及其对环境变化的适应机制。

Phosphorus(P)is one of the key elements that affecting plant growth,and below-ground foraging plasticity of fine roots is an important way for plants to improve the absorption of soil P.Under natural environmental conditions,heterogeneous or patchy distributions of soil nutrients have been well documented,especially for relatively immobile nutrients such as P.It is unclear how plants adjust the plastic responses of different below-ground foraging traits to nutrient patches,and the prediction of plastic responses of specific fine root traits to below-ground foraging traits is more uncertain.In this paper,the influencing factors of plant below-ground foraging were summarized,and the plastic responses of fine roots(morphology,architecture,proliferation,chemistry,and physiology)and mycorrhizal fungi to P-rich patches were expounded.The differences of below-ground foraging traits and plastic responses between arbuscular mycorrhizal and ectomycorrhizal tree species were analyzed from the aspects of fungal colonization mode,root morphology structure and nutrient acquisition strategies.Based on the carbon cost hypothesis of below-ground foraging,it was considered that morphological plasticity and physiological plasticity of fine roots were the results of resource competition in many cases.The proliferation plasticity of fungal mycelia seemed to be more economically significant for plants,but when both root and mycorrhizal fungi were present in nutrient patches,root proliferation was more responsive than fungal response.The prediction of nutrient foraging plasticity by fine root traits was also discussed,and it was pointed out that fine root diameter was a good predictor of changes in below-ground foraging traits.Finally,focusing on the shortcomings of the current research on the below-ground foraging plasticity of plants,the future research directions were proposed from the aspects of below-ground foraging foraging plasticity framework,below-ground foraging mechanism,prediction of fine root traits on the plasticity of plant nutrient acquisition,and the relationship between fine root foraging plasticity and defense plasticity,which would be helpful to understand the strategies of plant below-ground P acquisition and its adaptation mechanisms to environmental changes.