Yield response of winter wheat to chronic doses of ozone

Abstract

The relative sensitivity of 11 soft red winter wheat, Triticum aestivum L. cultivars, exposed as young plants to ambient levels of ozone (O₃) was determined. On the basis of the shoot dry weight response, the cultivar Holly was determined to be significantly more sensitive than Oasis or Coker 47-27; Blueboy II showed intermediate sensitivity. Plants of these four cultivars, grown in pots or in the ground, were exposed for 54 days in open-top field chambers to different O₃ concentrations added to existing levels of ambient oxidants for 7 h/day. The effects of O₃ on foliar injury, growth, and yield were determined. For the four cultivars combined, the threshold O₃ concentration (7 h/day seasonal mean) for significant injury and decreased growth and yield was between 0.06 and 0.10 ppm. For potted plants exposed to 0.10 and 0.13 ppm O₃, seed weight yields were 10 and 27% less, respectively, than for those grown in "charcoal-filtered-air" chambers (0.03 ppm O₃). For plants in the ground exposed to 0.10 and 0.13 ppm O₃, the yields were 16 and 33% less, respectively, than for those at 0.03 ppm O₃. The relative sensitivity of cultivars to O₃ as young plants could not be used to predict O₃ effects on seed yield.