ABSTRACT

Pima cotton was grown in field exposure chambers exposed to a range of ozone concentrations. The ratio of sucrose to raffinose series sugars was examined in source and sink tissues and in aphid honeydew as a surrogate for phloem sap. The profile of sugars did not change substantially in source leaves. The ratio of sucrose to raffinose series sugars (raffinose plus stachyose plus verbascose) declined significantly in fine root tissue with increasing ozone. The composition of honeydew also declined, though not as dramatically as fine root tissue. These results are not conclusive but are consistent with the hypothesis that ozone alters the apoplastic loading of sucrose into the phloem more than it alters the symplastic loading of raffinose series sugars.