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. Phloem 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.