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The adverse effects of tropospheric ozone (O 3 ) on crop photosynthesis, growth and yield have been documented in numerous studies over the last decades, but little information from field experimentation exists on how modern European winter wheat cultivars respond to O 3 . Two winter wheat cultivars (Astron and Pegassos) differing in development characteristics were exposed to non-filtered ambient air or non-filtered air plus 30 ppb and non-filtered air plus 60 ppb O 3 (8 h day À1 ) in open-top field chambers. At several dates during growth, green leaf area was determined by destructive harvests. Leaf gas exchange, pigment content and xanthophyll cycle activity, and photochemical efficiency by chlorophyll a fluorescence were measured. O 3 exposure induced accelerated senescence with no difference between cultivars. Photosynthesis declined especially in Pegassos; however, stomatal conductance was hardly affected by O 3 . Pigment contents were reduced by O 3 exposure, and de-epoxidation index increased. Photochemical efficiency (F v /F m ) declined, whereas actual quantum yield (Φ PSII ) did not respond to O 3 . O 3 exposure reduced grain yield in both cultivars. However, yield of Pegassos was more affected by O 3 exposure than yield of Astron, suggesting a higher O 3 sensitivity of Pegassos. The data presented in this manuscript indicate a need to test whether high-yield varieties such as Pegassos are particularly sensitive to O 3 exposure.

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Background: Ample quantities of ashes generated from domestic biomass energy combustion in Ghanaian kitchens are currently disposed of despite their potential agricultural value. This study aimed to investigate the potential agricultural value of charcoal and firewood ashes in terms of differences in the chemical and mineralogical compositions, and to identify the suitability of aqua regia, H 2 SO 4 , vinegar and distilled water to extract plant nutrients (Ca, Mg, K, Na, and P). The chemical compositions were determined by atomic absorption spectrometry after extractions with aqua regia, H 2 SO 4 , vinegar and distilled water while mineralogy was determined by X-ray powder diffraction. Results: The charcoal ash had 0.2 units, 13 ds m −1 , and 7% higher (P < 0.05) pH, EC, and CCE, respectively, than the firewood ash, whereas the latter had 6, 17, 43, and 139 µg g −1 higher (P < 0.05) As, Cu, Mg, and Zn contents, respectively, and more minerals with 86% being Mg-rich. Calcite and calcium oxide were the dominant minerals occurring in both ashes followed by calcium manganate (CaMnO 3). Aqua regia and vinegar were suitable for Ca, acidic solutions for Mg, H 2 SO 4 and aqua regia for P with Na and K being virtually soluble in all solutions. Lead, Mn, Ni, and Zn had values in the order of hundreds. Conclusions: Although the ashes differ, they both contain trace elements whose bioavailability may differ and may not necessarily lead to plant uptake after field application. This offers an opportunity for further research into the threshold trace element contents of wood ash and their relationship with plant uptake in different soil pH and soil types.

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