Effect of Infection by Microsphaera Alphitoides (Powdery Mildew) on Carbohydrate Levels and Translocation in Seedlings of Quercus Robur

SUMMARY As infection of leaves of Quercus robur by Microsphaera alphitoides (powdery mildew) progressed, levels of total carbohydrate varied as first the rate of net photosynthesis declined and then an abnormal pattern of translocation was established. Infected leaves exported a smaller proportion of their photosynthate than did healthy leaves and imported a greater proportion of the photosynthate of healthy leaves on the same plant than did healthy leaves on healthy plants. Infection caused a decrease in the amounts of sucrose and insoluble glucose and an increase in amounts of glucose and fructose in leaf tissue. Evidence is presented that glucose and fructose were transferred to the fungus where they were converted to polyhydric alcohols and trehalose.