Abstract: The effect of doubled CO2 on the chlorophyll-protein complexes of the leaves of soybean ( Glycine max L., Ca plants), cucumber ( Cucumis sativus L., C3 plant), millet ( Setaria italica (L.) Beauv., not a very typical C4 plant) and corn (Zea mays L. ,C4 plant) was studied. Experi- mental plants were pot-cultured in polyethylene membrane (or glass) open top cultured chambers. After sowing, C02 was kept immediately either at ambient ( (350 ± 10) x 10-6) concentration for the control or at doubled CO2 ((700 ± 10) x 10-6) concentration for the treatment chambers. The chlorophyll-protein complexes of the thylakoid membrane of the plants were resolved by disk SDS- PAGE. The results showed that after doubled CO2 treatment,either in the soybean and cucmnber,or in the millet, the quantity of polymer state of PS Ⅱ light-harvesting chlorophyll a/b-protein complex (LHC Ⅱ ) had increased as the monomer state of LHC Ⅱ decreased. But such response to doubled CO2 was not found in corn, the C4 plant. The change of the state of LHC Ⅱ in soybean etc. might be an adaptive effect of plant photosynthetic mechanism to the long term elevated CO2. Thus it could increase the efficiency of the absorption, transfer and conversion of light energy in plant photosynthesis, and support the high efficiency of photosynthetic carbon assimilation.

Key words: CO2 concentration doubling, Photosystem Ⅰ, Photosystem Ⅱ, Chlorophyll-protein complex, Photosystem Ⅱ light-harvesting chlorophyll a/b-protein complex, SDS-polyacrylamide gel electrophoresis