四种常见树木叶片光合模型关键参数对臭氧浓度升高的响应

随着城市化进程的加快, 臭氧(O₃)已经成为中国夏季首要大气污染物。已有研究表明O₃通过气孔进入叶片显著抑制光合作用, 影响陆地生态系统碳水循环过程。但是O₃浓度升高对植物光合和气孔导度模型关键参数影响的研究仍然缺乏。该研究利用开顶式气室, 设置两个O₃处理(CF, 过滤空气; E-O₃, 未过滤空气+ 60 nmol·mol^-1 O₃), 选用4种常见的树木(茶(Camellia sinensis)、复叶槭(Acer negundo)、栾树(Koelreuteria paniculata)和蒙古栎(Quercus mongolica)), 通过测定叶片气体交换参数, 探究O₃浓度升高对植物光合和气孔导度模型关键参数的影响。结果表明: O₃浓度升高显著降低了4种植物的饱和光合速率和光合生化模型参数叶肉导度, 但是O₃对光合生化模型参数最大羧化速率和最大电子传递速率的负效应在不同树种间存在差异。此外, 不同植物气孔导度对O₃的响应也存在差异。通过对最优化气孔导度模型进行参数化, 结果表明O₃显著提高了蒙古栎和复叶槭的斜率参数(g₁), 并显著增加了茶的气孔导度模型截距参数(g₀), 但降低了复叶槭的g₀。在不同O₃处理下4种树木的内源水分利用效率与g₁呈显著线性负相关关系。综上所述, O₃浓度升高显著影响光合生化和气孔导度模型关键参数。

Response of key parameters of leaf photosynthetic models to increased ozone concentration in four common trees

Aims With fast urbanization in China, ground-level ozone (O₃) has become the major atmospheric pollutant in summer. It was documented that O₃ enters leaves through stomata, inhibits photosynthesis, and alters the carbon and water cycles in terrestrial ecosystems. However, few studies have investigated the key parameters of photosynthetic and stomatal conductance models in response to elevated O₃ concentration. Methods In this study, plants of four common tree species (Camellia sinensis, Acer negundo, Koelreuteria paniculata and Quercus mongolica) were exposed to two O₃ treatments (CF, charcoal-filtered air; E-O₃, ambient air + 60 nmol·mol^-1 O₃) in open top chambers. The effects of elevated O₃ concentration on key parameters of photosynthetic and stomatal conductance models were explored using data from leaf gas exchange measurements. Important findings Our results indicated that elevated O₃ concentration significantly decreased the light-saturated photosynthesis and mesophyll conductance in the four species. However, species showed distinct responses of the maximum rate of Rubisco carboxylation and the maximum rate of electron transport to elevated O₃ concentration. The response of stomatal conductance to O₃ was also different among species. We found that elevated O₃ concentration significantly increased the slope parameters (g₁) of Q. mongolica and A. negundo; however, the intercept parameter of stomata model in C. sinensis was decreased in A. negundo. The intrinsic water- use efficiency of the four species was negatively correlated with g₁ across O₃ treatments. All in all, elevated O₃ concentration significantly affected key parameters of the photosynthetic and stomatal conductance models. This study could provide the foundation and support for improving the accuracy of terrestrial ecosystem models under elevated O₃ concentration.