- • Tropospheric ozone (O3) is damaging to plants and decreases crop yields. This study investigated the role of two plant growth regulators in affecting wheat-yield responses to elevated [O3]. In a controlled factorial experiment, wheat plants were treated with combinations of Ethephon, which releases ethene, Chlormequat, which blocks gibberellin synthesis, and elevated [O3].
- • Spring-wheat plants were subjected to lifelong exposures to ambient or moderately elevated [O3]. At flag-leaf emergence, the plants were treated with Ethephon and/or Chlormequat, or untreated (controls). Gas-exchange measurements were made at anthesis; morphology, biomass, and yield components were recorded at harvest.
- • Elevated [O3] accelerated development and decreased the number of grains per ear and ears per plant. Chlormequat abolished these O3 effects, protecting against yield reduction though not biomass loss. Ethephon treatment partially protected against O3-induced biomass loss though not yield reduction.
- • This study suggests that the effects of elevated [O3] on development and allocation are more important in determining the yield response of wheat than the accompanying decline in photosynthesis and biomass accumulation.