Chemische und physikalische Reaktionen SO2-begaster Pflanzen und Blätter

Wien

1971

S. 209-231

8 Abb., 3 Tab., 5 Lit. Ang.

Unselbständiges Werk

200144237

Intact plants of Brassica napus, Nicotiana tabacum, Vicia faba and Borago officinalis were subjected to continuous exposure to SO2 and their leaves examined at different stages of damage for changes in certain vital substances. Even before there were any visible signs of damage to the leaves of Brassica napus the concentrations of thiamin, pantothenic acid and folic acid were found to be lower. In necrotic areas the amounts of niacin und biotin were also found to be reduced. The influenae of SO2 on the energy level of the leaves was confirmed by measurement of the ATP concentrations. After exposure to 4,2 mg S02/m3 the leaves of Vicia faba partly showed a sizeable increase in the ATP level. A slight increase was also found in Nicotiana tabacum after exposure to 0,8 mgS02/m3. When more concentrated SO2 (4,8 mg/m3) was used, a reduction in the ATP concentrations was observed in Nicotiana tab. and Borago officinalis. Exposition to 0,8 mg SO2/m3 caused a slight increase in the activity of the NADP+-dependent GPD both in Vicia f. and in Nicotiana tab. The activity of this enzyme decreased considerably in concentrations of approx. 4,5mg SO2/m3. The lowest values were obtained both in the acute necrotic and chlorotic areas. The sensitivity of Vicia f. to SO2 could be increased by prior treatment of the plants with kinetin. Measurement of the gas exchange in certain leaves, before, during and after exposition to SO2 showed a strong dependence of the assimilation of CO2 on the absorption of SO2 and a correlation to transpiration. There would appear to be a certain feed-back between photosynthesis and absorption of SO2 through the stomata which seems partly to express itself in a welldefined oscillation between photosynthesis, transpiration and absorption of SO2.