Photosynthesis and Yield of Wheat (Triticum aestivum) Treated with Fungicides in a Disease-Free Environment. E. J. Lorenz, Research Associate, Soil and Crop Sciences Department, Texas A&M University, College Station 77843-2474. J. T. Cothren, Associate Professor, Soil and Crop Sciences Department, Texas A&M University, College Station 77843-2474. Plant Dis. 73:25-27. Accepted for publication 29 June 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0025.

Fungicidal growth-regulating effects of a tank mixture of triadimefon (Bayleton 50 WP) and zinc ion + manganese ethylene bisthiocarbamate) (Dithane M-45) were evaluated on the soft red winter wheat cultivar Coker 762. Analysis of photosynthesis, leaf conductance, and transpiration 2 and 6 days after foliar application indicated no significant differences between fungicide-treated plants and nontreated controls. Fungicide treatments caused significant (P = 0.05) reduction in germination for seed harvested from plants sprayed at Feekes growth stages 9.0 + 10.3 and 10.3 but not at stage 9.0. Carryover plant growth-regulating effect from fungicide application increased chlorophyll content from 4 to 40% over controls for dark-grown seedlings after exposure to light. This research indicates that any benefit of increased grain yield from foliar-applied fungicides other than by the control of pathogens is unlikely to occur from improved leaf gas exchange and that a carryover effect from fungicides does influence subsequent germination.