Ozone impacts on cotton: towards an integrated mechanism

Vegetation removes tropospheric ozone (O-3) mainly through uptake by stomata. O-3 reduces growth, photosynthesis, and carbohydrate allocation. Effects on mesophyll photosynthesis, may reducing carbohydrate source strength and, indirectly, carbohydrate translocation. Alternatively direct translocation, itself, could explain all of these observations. O-3-reduced root proliferation inhibits exploitation of soil resources and interferes with underground carbon sequestration. Simulations with cotton suggest O-3-disrupted root development could indirectly reduce shoot photosynthesis. Strong evidence for O-3 impacts on both carbon assimilation and carbon translocation exists, but data determining the primacy of direct or indirect O-3 effects on either or both processes remain inconclusive. Pholoem loading may be particularly sensitive to O-3. Further research on metabolic feedback control of carbon assimilation and phloem loading activity as affected by O-3 exposure is required. (C) 2003 Elsevier Ltd. All rights reserved.