Plants should have the ability to perceive physiological changes within their branches when infected by mistletoes, adjusting the use of resources between infected and uninfected branches which can be crucial for their survival in the long-term. Here we investigated how branches infected by the mistletoe Passovia ovata (Pohl ex DC.) Tiegh. and uninfected branches within the same individual tree respond to seasonal environmental changes across two hosts of contrasting leaf phenology (the evergreen Miconia albicans (SW.) Triana and the deciduous Byrsonima verbascifolia (L.) DC.). We measured key leaf traits (instantaneous gas exchange rates, diurnal courses of stomatal conductance, leaf water potential, specific leaf area and leaf macronutrient concentrations) during the peak of the wet and dry season in a seasonal savanna of central Brazil. Pre-dawn leaf water potentials were consistently more negative for infected branches of both hosts, suggesting that overnight water refilling of infected branches was more limited. However, infected and uninfected branches exhibited similar leaf water potentials at midday, suggesting that they undergo similar imbalances in water supply and demand during periods of high atmospheric evaporative demand. Infected and non-infected branches of the evergreen mistletoe showed tighter regulation of water loss, whereas infected branches of the deciduous host were less constrained in regulating leaf transpiration. We also found differences for nutrient concentrations: N, P and K were lower, while Ca was higher in leaves of infected branches. Physiological changes induced by mistletoe infection affected host performance, and were reflected in water and nutrient use differences between infected and uninfected branches. Our findings show that infection responses by mistletoes can be detected between branches within individual trees, and that host species with distinct patterns of leaf phenology are capable to adjust, at the individual level, to cope with mistletoe's imposed physiological stress throughout the year.

当被槲寄生感染时，植物应该能够感知其枝条内的生理变化，调整感染和未感染枝条之间的资源使用，这对于它们的长期生存至关重要。在这里，我们调查了槲寄生Passovia ovata (Pohl ex DC.) Tiegh如何感染树枝。和未受感染的同一棵树内的枝条对两个对比叶物候宿主（常绿Miconia albicans (SW.) Triana 和落叶Byrsonima verbascifolia）的季节性环境变化做出反应(L.) DC.)。我们在巴西中部季节性稀树草原的湿季和干季高峰期测量了关键的叶片性状（瞬时气体交换率、气孔导度的昼夜变化、叶水势、比叶面积和叶片常量营养素浓度）。黎明前叶水势对于两个宿主的受感染枝条始终为负值，这表明受感染枝条的夜间补水更为有限。然而，受感染和未受感染的树枝在中午表现出相似的叶水势，这表明它们在大气蒸发需求高的时期经历了相似的水供需失衡。常绿槲寄生的感染和未感染分支表现出更严格的水分流失调节，而落叶寄主受感染的枝条在调节叶片蒸腾作用方面受到的限制较少。我们还发现营养浓度的差异：N、P 和 K 较低，而受感染树枝的叶子中的 Ca 较高。槲寄生感染引起的生理变化影响寄主性能，并反映在感染和未感染枝条之间的水分和养分利用差异上。我们的研究结果表明，槲寄生的感染反应可以在个别树木的树枝之间检测到，并且具有不同叶片物候模式的宿主物种能够在个体水平上进行调整，以应对槲寄生全年施加的生理压力。而受感染的枝条叶子中的钙含量较高。槲寄生感染引起的生理变化影响寄主性能，并反映在感染和未感染枝条之间的水分和养分利用差异上。我们的研究结果表明，槲寄生的感染反应可以在个别树木的树枝之间检测到，并且具有不同叶片物候模式的宿主物种能够在个体水平上进行调整，以应对槲寄生全年施加的生理压力。而受感染的枝条叶子中的钙含量较高。槲寄生感染引起的生理变化影响寄主性能，并反映在感染和未感染枝条之间的水分和养分利用差异上。我们的研究结果表明，槲寄生的感染反应可以在个别树木的树枝之间检测到，并且具有不同叶片物候模式的宿主物种能够在个体水平上进行调整，以应对槲寄生全年施加的生理压力。