INFLUENCE OF CO2 AND SO2 ON GROWTH AND STRUCTURE OF PHOTOSYSTEM-II OFTHE CHINESE TUNG-OIL TREE ALEURITES MONTANA

Three months old plants of the Chinese tung-oil tree Alenrites montana were cultivated for 4 months in air containing an increased amount of 700 ppm CO2. During the exposure to 700 ppm CO2 the plants exhibited a considerably stronger growth (30-40%) in comparison to the control p lants (grown in normal air). In these CO2-plants during the entire ana lyzing period the amount of soluble proteins, of soluble sugars and th e chlorophyll content were lower than in control plants. The protein c ontent, referred to leaf area, increased during this time in both plan t types by approx. 50% but with a different time course. The increase is faster in CO2-plants compared to control plants, and ends up with s imilar values in both plants after 4 months. No difference is seen bet ween sun and shade leaves. The chlorophyll content in both sun and sha de leaves is 20% lower in CO2-plants. Whereas the chlorophyll content in sun leaves stays constant during development, it has increased in s hade leaves by 20% at the end of the 4 months period. The content of s oluble sugars is lower in CO2-plants compared to control plants. The d ifference is bigger in sun leaves than in shade leaves. The ribulose 1 .5-bisphosphate carboxylase/oxygenase content almost doubles within th e experimentation period, but seems to be subject to large variations. CO2-plants contain in general less ribulose 1.5-bisphosphate carboxyl ase/oxygenase than control plants. The content of coupling factor of p hotophosphorylation is 20% lower in CO2-plants when compared to contro l plants and remains during development more constant in CO2-plants. T he molecular structure of the photosystem II-complex undergoes under t he influence of the increased CO2-content a quantitative modification. The light harvesting complex (LHCP) and the extrinsic peptide with th e molecular mass of 33 kDa increase in CO2-plants. Gassing with SO2 (0 .3 ppm in air) leads to a strong damage of the plants. The damaging in fluence is already seen after 6 days and leads to a partial leaf-shedd ing of the tree. In the visually still intact remaining leaves the chl orophyll content referred to unit leaf area decreases by 63%, that of soluble sugars by 65%, the content of soluble proteins and that of Rub isco decrease by 26% and 36% respectively. The light harvesting comple x and the chlorophyll-binding peptides (43 and 47 kDa) increase wherea s the extrinsic peptides decrease. It looks as if the simultaneous app lication of SO2 (0.3 ppm) and increased CO2 (700 ppm) releaves the dam aging effect of SO2. Plant growth does not exhibit a difference in com parison to control plants. Soluble proteins and chlorophyll increase b y 27% and 33% and the ribulose 1.5-bisphosphate carboxylase/oxygenase content as well as that of soluble sugars increases by 18 respectively 14%. The peptide composition of photosystem II shows a quantitative m odification. The LHCP increases and the chlorophyll-binding peptides a nd the peptides with a molecular mass smaller than 24 kDa are reduced. The quantity of extrinsic peptides appears unchanged. Ribulose 1,5-bi sphosphate carboxylase/oxygenase and the CF1-complex of Aleurites are immunochemically only partially identical to the corresponding enzymes of Nicotiana tabacum as demonstrated by tandem-cross-immune electroph oresis.