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Response of gas exchange and yield components of field-grown Triticum aestivum L. to elevated ozone in China

Feng, Z.-Z., Yao, F.-F., Chen, Z., Wang, X.-K., Zheng, Q.-W., Feng, Z.-W.
Photosynthetica 2007 v.45 no.3 pp. 441-446
Triticum aestivum, air, carbon dioxide, diurnal variation, filling period, florets, gas exchange, leaves, light intensity, ozone, photosynthesis, planting, stomatal conductance, stomatal movement, winter wheat, yield components, China
To assess photosynthesis and yield components’ response of field-grown wheat to increasing ozone (O₃) concentration (based on diurnal pattern of ambient O₃) in China, winter wheat (Triticum aestivum L.) cv. Jia 403 was planted in open top chambers and exposed to three different O₃ concentrations: O₃-free air (CF), ambient air (NF), and O₃-free air with additional O₃ (CF+O₃). Diurnal changes of gas exchange and net photosynthetic rate (P N) in response to photosynthetic photon flux density (PPFD) of flag leaves were measured at the filling grain stage, and yield components were investigated at harvest. High O₃ concentration altered diurnal course of gas exchange [P N, stomatal conductance (g ₛ), and intercellular CO₂ concentration (C ᵢ)] and decreased significantly their values except for C ᵢ. Apparent quantum yield (AQY), compensation irradiance (CI), and saturation irradiance (SI) were significantly decreased, suggesting photosynthetic capacity was also altered, characterized as reduced photon-saturated photosynthetic rate (P Nₘₐₓ). The limit of photosynthetic activity was probably dominated by non-stomatal factors in combination with stomatal closure. The significant reduction in yield was observed in CF+O₃ treatment as a result of a marked decrease in the ear length and the number of grains per ear, and a significant increase in the number of infertile florets per ear. Even though similar responses were also observed in plants exposed to ambient O₃ concentration, no statistical difference was observed at current ambient O₃ concentration in China.