Abstract
The tropical-grown crops common bean (Phaseolus vulgaris), mung bean (Vigna radiate), cowpea (Vigna unguiculata), pearl millet (Pennisetum glaucum), finger millet (Eleusine coracana), amaranth (Amaranthus hypochonriacus), sorghum (Sorghum bicolour) and wheat (Triticum aestivum) were exposed to different concentrations of the air pollutant ozone in experimental Solardome facilities. The plants were exposed to ozone treatments for between one and four months, depending on the species. There was a large decrease in yield of protein-rich beans and cowpeas with increasing ozone exposure, partly attributable to a reduction in individual bean/pea weight. Size of individual grains was also reduced with increasing ozone for African varieties of wheat. In contrast, the yield of amaranth, pearl millet and finger millet (all C4 species) was not sensitive to increasing ozone concentrations and there was some evidence of an increase in weight of individual seedheads with increasing ozone for finger millet. Sorghum did not reach yield, but was not sensitive to ozone based on changes in biomass. Dose-response relationships for these crop species demonstrate that tropospheric ozone pollution could reduce yield of important crops, particularly legumes, in tropical regions such as sub-Saharan Africa.
Highlights
Tropospheric ozone is one of the most important global air pollutants, formed from photochemical production by hydroxyl radical oxidation of molecules including carbon monoxide (CO) and hydrocarbons in the presence of nitrogen oxides (NOx) [31]
This study allows improved risk assessment for the impact of ozone pollution on growth of tropical crops, with the results based on re-creating tropical conditions in ozone-exposure facilities in the UK to enable ozone-sensitivity of crops to be experimentally tested in controlled conditions
The results indicate that there is a risk to protein consumption for subsistence farmers in tropical regions e.g. Africa and India, since the yield of proteinrich beans and cowpeas was reduced by ozone pollution, but the yield of carbohydrate-rich millets was not affected within the concentration range used in this study
Summary
Tropospheric ozone is one of the most important global air pollutants, formed from photochemical production by hydroxyl radical oxidation of molecules including carbon monoxide (CO) and hydrocarbons in the presence of nitrogen oxides (NOx) [31]. Global production losses of up to 12% for wheat and up to 16% for soybean due to ambient ozone were shown based on ozone concentration metrics for 2000 [41] and global production losses of 8.5–14% were predicted for soybean, and 3.9–15% for wheat for the year 2000 [3] These studies use dose-response relationships established mostly from European and/or North American data and which may not be representative of other regions [9,11]. We combined data from different varieties of the same crop to establish dose-response relationships based on stomatal ozone uptake that can be used to improve risk assessment of ozone pollution for tropical agricultural crops
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