Changes in the transpiration rate of barley plants cv. “Profesor Schiemann” infected with powdery mildew in light and in darkness

The transpiration rate of intact spring barley plants, cv. Profesor Schiemann resistant to powdery mildew was studied separately in light and in darkness. At the first stage of pathogenesis the fungus temporarily reduced the transpiration rate of the host plants in light (E ₁). The transpiration rate in darkness (E _d) was not influenced in this period and only in the period of formation of necrotic spotsE _d in the host plants was somewhat higher than that in the control plants.E ₁ of the host plants gradually reached the level of the control plants in this period. The fungus considerably reduced the rationE ₁/E _d. The differences in this ratio between infected and control plants increased in the susceptible cultivar but were moderated in the course of necrobiosis.