Growth and Structure of Photosystem II of the Chinese Tung-Oil Tree Aleurites montana

Three months old plants of the Chinese tung-oil tree Aleurites montana were cultivated for 4 months in air containing an increased amount of 700 ppm C 0 2. During the exposure to 700 ppm C 0 2 the plants exhibited a considerably stronger growth (30-40% ) in compari­ son to the control plants (grown in normal air). In these C02-plants during the entire analyz­ ing period the amount of soluble proteins, of soluble sugars and the chlorophyll content were lower than in control plants. The protein content, referred to leaf area, increased during this time in both plant types by approx. 50% but with a different time course. The increase is faster in C02-plants compared to control plants, and ends up with similar values in both plants after 4 months. No difference is seen between sun and shade leaves. The chlorophyll content in both sun and shade leaves is 20% lower in C02-plants. Whereas the chlorophyll content in sun leaves stays constant during development, it has increased in shade leaves by 20% at the end of the 4 months period. The content of soluble sugars is lower in C 0 2-plants compared to control plants. The difference is bigger in sun leaves than in shade leaves. The ribulose 1.5-bisphosphate carboxylase/oxygenase content almost doubles within the experimentation period, but seems to be subject to large variations. C02-plants contain in general less ribulose 1.5-bisphosphate carboxylase/oxygenase than control plants. The content of coupling factor of photophosphorylation is 20% lower in C02-plants when compared to control plants and remains during development more constant in C02-plants. The molecular structure of the photosystem II-complex undergoes under the influence of the increased C 0 2-content a quantitative modification. The light harvesting complex (LHCP) and the ex­ trinsic peptide with the molecular mass of 33 kDa increase in C02-plants. Gassing with S 0 2 (0.3 ppm in air) leads to a strong damage of the plants. The damaging influence is already seen after 6 days and leads to a partial leaf-shedding of the tree. In the visually still intact remaining leaves the chlorophyll content referred to unit leaf area decreases by 63%, that of soluble sugars by 65%, the content of soluble proteins and that of Rubisco decrease by 26% and 36% respectively. The light harvesting complex and the chlorophyll-binding peptides (43 and 47 kDa) increase whereas the extrinsic peptides decrease. It looks as if the simultaneous application of S 0 2 (0.3 ppm) and increased C 0 2 (700 ppm) releaves the damaging effect of S 0 2. Plant growth does not exhibit a difference in comparison to control plants. Soluble proteins and chlorophyll increase by 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 modification. The LHCP increases and the chlorophyll-binding peptides and the peptides with a molecular mass smaller than 24 kDa are reduced. The quantity of extrinsic peptides appears unchanged. Ribulose 1,5-bisphosphate carboxylase/oxygenase and the CFj-complex of Aleurites are immunochemically only partially identical to the corresponding enzymes of Nicotiana taba­ cum as demonstrated by tandem-cross-immune electrophoresis.