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John W. Moon Jr.

CO2 assimilation (20-25%) and carboxylation efficiency (30-35%) was greater (P < 0.01) in Fragaria chiloensis, clone RCP37 than F. ananassa cv. `Midway'. Both leaf thickness (P < 0.05) and internal mesophyll cell surface area (P < 0.01) was greater in RCP37 than `Midway'. No differences in Rubisco specific activity were observed between the 2 species, whereas Rubisco amount was 40% greater (P < 0.01) and leaf nitrogen per area was 30-35% greater in RCP37 compared to `Midway'. Potential for selection of clones with high photosynthesis by screening for soluble protein will be discussed.

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John W. Moon Jr.

`Midway' and `Raritan' strawberry cultivars were grown for six weeks under ambient (350) or twice ambient (700 μmol mol-1) CO2 Photosynthetic inhibition (40-50%) was observed in both cultivars as indicated by reductions (P < 0.001) in CO2 assimilation, carboxylation efficiency, stomatal conductance, and apparent quantum yield. Growth under high CO2 did not affect Rubisco activity in either cultivar, whereas Rubisco activation state (%) was reduced (72.9 to 67.6) in `Midway' and increased (70.8 to 83.3) in `Raritan' compared to ambient CO2 grown plants. Soluble and Rubisco protein decreased 10-15% in `Midway' and 40-45% in `Raritan' when grown under high CO2 Thus, `Raritan' reduced the amount of protein partitioned into photosynthetic enzymes under conditions of photosynthetic inhibition, whereas `Midway' experiences Rubisco deactivation. The reduction in Rubisco protein appears to be under the regulation of chloroplast genes.