Plant growth regulators control ozone damage to wheat yield

Tropospheric ozone (O-3) is damaging to plants and decreases crop yields. T his study investigated the role of two plant growth regulators in affecting wheat-yield responses to elevated [O-3]. In a controlled factorial experim ent, wheat plants were treated with combinations of Ethephon, which release s ethene, Chlormequat, which blocks gibberellin synthesis, and elevated [O- 3]. Spring-wheat plants were subjected to lifelong exposures to ambient or mode rately elevated [O-3]. At flag-leaf emergence, the plants were treated with Ethephon and/or Chlormequat, or untreated (controls). Gas-exchange measure ments were made at anthesis; morphology, biomass, and yield components were recorded at harvest. Elevated [O-3] accelerated development and decreased the number of grains p er ear and ears per plant. Chlormequat abolished these O-3 effects, protect ing against yield reduction though not biomass loss. Ethephon treatment par tially protected against O-3-induced biomass loss though not yield reductio n. This study suggests that the effects of elevated [O-3] on development and a llocation are more important in determining the yield response of wheat tha n the accompanying decline in photosynthesis and biomass accumulation.