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Effects of Maize Dwarf Mosaic Virus on Water Relations of Corn. Donald W. Lindsey, Former Graduate Research Assistant, Department of Botany and Microbiology, Auburn University Agricultural Experiment Station, Auburn, Alabama 36830, Present address of senior author: Science Department, Walters State Community College, Morristown, Tennessee; Robert T. Gudauskas, Professor, Department of Botany and Microbiology, Auburn University Agricultural Experiment Station, Auburn, Alabama 36830. Phytopathology 65:434-440. Accepted for publication 5 November 1974. DOI: 10.1094/Phyto-65-434.

Transpiration rates of maize dwarf mosaic virus (MDMV)-infected corn seedlings were reduced 15-40%, compared to healthy seedlings grown in soil or liquid culture without water stress or under increasing water stress in sealed pots. Onset of reduced transpiration was coincident with appearance of symptoms in infected leaves. Leaf water potentials of MDMV-infected seedlings were equal to, or higher than, those of healthy seedlings, which indicated that reduced transpiration was not caused by increased water stress in infected plants. Measurements of diffusive resistances of leaves, and direct observation of epidermal impressions, indicated that stomatal apertures were reduced in leaves of MDMV-infected plants. Movement of potassium ions into guard cells of healthy and MDMV-infected leaves was correlated with stomatal opening; potassium content of guard cells of MDMV-infected leaves was lower than that of guard cells of healthy leaves. Reduced transpiration by MDMV-infected corn seedlings appeared due to restriction of stomatal opening that was associated with reduced uptake of potassium by guard cells of infected leaves.