Photosynthetic traits and growth of Quercus mongolica var. crispula sprouts attacked by powdery mildew under free-air CO2 enrichment

Abstract

To predict the performance of coppice forests with Japanese oak (Quercus mongolica var. crispula) in future changing environment, we studied the growth, photosynthesis, and powdery mildew (Erysiphe alphitoides) infection of sprouts of Japanese oak under free-air CO2 enrichment. Elevated CO2 reduced powdery mildew infection in both leaves of the shoot emerged in spring (1st flush) and the lammas and proleptic shoots (2nd flush) of sprouts. We observed significant increase in the net photosynthetic rate at growth CO2 concentration (i.e., 370 and 500 μmol mol−1 for ambient and elevated CO2 treatments, respectively) in both 1st and 2nd flush leaves of sprouts grown under elevated CO2. On the other hand, no significant increase in net photosynthetic rate under elevated CO2 was found before cutting. The photosynthetic activity of 2nd flush leaves in the sprouts under ambient condition was greatly reduced by severe infection to powdery mildew. Growth of sprouts was enhanced in the elevated CO2 condition. We conclude the growth enhancement in Japanese oak sprouts under elevated CO2 in the present study was achieved not only by physiological response (i.e., photosynthetic stimulation) but also by disease interaction.