Although ozone (O3) concentration and nitrogen (N) availability are well known to affect plant physiology, their impacts on the photosynthetic temperature response are poorly understood. We addressed this knowledge gap by exposing seedlings of hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation in a factorial experiment. E-O3 decreased light-saturated net photosynthesis (Asat), mesophyll conductance (gm) and apparent maximum rate of carboxylation (Vcmax, based on intercellular CO2 concentration) but not actual Vcmax (based on chloroplast CO2 concentration) and increased respiration in light (Rd) at 25 °C. Nitrogen fertilization increased Asat, gm, Vcmax and the maximum rate of electron transport (Jmax) and reduced Rd at 25 °C and the activation energy of actual Vcmax. No E-O3 or E-O3 x N interaction effects on the temperature response parameters were detected, simplifying the inclusion of O3 impacts on photosynthesis in vegetation models. gm peaked at 30 °C, apparent Vcmax and Jmax at 32-33 °C, while the optimum temperatures of actual Vcmax and Jmax exceeded the measured temperature range (15-35 °C). Ignoring gm would, thus, have resulted in mistakenly attributing the decrease in Asat at high temperatures to reduced biochemical capacity rather than to greater diffusion limitation.

中文翻译：

---

臭氧，氮素有效性和叶肉电导率升高对杨树叶片光合参数温度响应的影响。

尽管众所周知臭氧（O3）的浓度和氮（N）的可用性会影响植物生理，但对光合作用温度响应的影响知之甚少。我们通过在因子分析实验中将杂交的杨树克隆'107'（Euramericana cv。'74 / 76'）的幼苗暴露于升高的O3（E-O3）和N利用率变化来解决这一知识鸿沟。E-O3降低了光饱和净光合作用（Asat），叶肉电导（gm）和表观最大羧化速率（Vcmax，基于细胞间CO2浓度），但没有实际的Vcmax（基于叶绿体CO2浓度），并且增加了光的呼吸作用（ Rd）在25°C。施氮增加了Asat，gm，Vcmax和最大电子传输速率（Jmax），并降低了25°C时的Rd和实际Vcmax的活化能。未检测到E-O3或E-O3 x N相互作用对温度响应参数的影响，从而简化了O3对植被模型中光合作用的影响。gm在30°C达到峰值，表观Vcmax和Jmax在32-33°C，而实际Vcmax和Jmax的最佳温度超过了测得的温度范围（15-35°C）。因此，忽略gm会导致将Asat在高温下的减少错误地归因于生化能力的降低而不是更大的扩散限制。