Ozone Fumigation in the Sun Crown of Norway Spruce : Expertentagung Waldschadensforschung im oestlichen Mitteleuropa und in Bayern

1991

S. 567-573

4 Abb., 11 Lit. Ang.

Unselbständiges Werk

200100857

Simulated daily courses of net photosynthesis and conductance were measured on Norway spruce twigs exposed to three different concentrations of O3 in the field. The treatments were charcoal-filtered air (CF), ambient air (A) and ambient air + 60 ppb O3 (A+60). Twigs remained in semi-climatised fumigation cuvettes for three months during summer 1990. Gas exchange was measured at the end of the fumigation period under identical chamber conditions with two fully climatised chambers in parallel. Ambient air O3 concentrations did not alter gas exchange parameters compared to CF twigs but a + 60 ppb O3 caused a twofold photosynthesis and conductance in the chambers was primarily influenced by twig position and changing external climatic conditions. A loss in the regulatory capacity of the stomata was observed in the A+60 twig. This can be an increasing risk of drought injury, especially in dry summers.