PREMISE Mistletoes parasitize many hardwood and softwood tree species; however, they play key roles in forest ecosystems. Adult individuals of Psittacanthus schiedeanus take up water and xylem nutrients from both deciduous and evergreen host trees, suggesting the ability to modify its physiology according to the availability of host resources. Yet, there is little information regarding the effects of mistletoes on their host trees from the eophyll stage to reproductive phases of the parasite. METHODS Taking advantage of the fact that P. schiedeanus can reach sexual maturity in 1 year, we investigated its physiological performance during development on deciduous (Liquidambar styraciflua) and evergreen (Quercus germana) host trees in a cloud forest in eastern Mexico. Variables related to chlorophyll fluorescence, carbon assimilation, photosynthetic pigments, and nitrogen, phosphorus, and carbon contents of the parasite and non-infected and infected hosts were analyzed in a nursery experiment. RESULTS Mistletoe had lower water-use efficiency and higher transpiration rates than the host species did. Despite the fact that P. schiedeanus obtained resources from species with differing phenology and resource availability, the parasite steadily improved its CO2 assimilation, electron transport rate, and nutrient content from seedling establishment to adult life stages. Mistletoe decreased the photosynthetic reactions of carbon metabolism in the deciduous host, photosynthetic light reactions in the evergreen host, and nutritional status of both host species, mostly in the evergreen host. CONCLUSIONS The hypothesis that mistletoes adjust their physiology according to the availability of host resources could extend to the early growth of the parasite.

中文翻译：

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新热带槲寄生的生态生理取决于其寄主的叶子物候

前提槲寄生寄生于许多硬木和软木树种；然而，它们在森林生态系统中发挥着关键作用。Psittacanthus schiedeanus 的成年个体从落叶和常绿寄主树中吸收水分和木质部养分，这表明能够根据寄主资源的可用性改变其生理机能。然而，关于槲寄生对寄主树从叶叶阶段到寄生虫繁殖阶段的影响的信息很少。方法 利用 P. schiedeanus 可在 1 年内达到性成熟的事实，我们研究了其在墨西哥东部云雾林中落叶（Liquidambar styraciflua）和常绿（Quercus Germana）寄主树发育过程中的生理表现。与叶绿素荧光、碳同化、在苗圃实验中分析了寄生虫和未感染和感染宿主的光合色素以及氮、磷和碳含量。结果槲寄生的水分利用效率比寄主物种低，蒸腾速率高。尽管 P. schiedeanus 从具有不同物候和资源可用性的物种中获得资源，但该寄生虫从幼苗建立到成年生命阶段稳步提高了其 CO2 同化、电子传递率和营养含量。槲寄生降低了落叶宿主中碳代谢的光合反应、常绿宿主中的光合光反应以及两种宿主物种的营养状况，主要是在常绿宿主中。