Effect of leaf variegation on acclimation of photosynthesis and growth response to elevated ambient CO2

Rooted cuttings of variegated (HV) and fully green (HG) varieties of Hedera helix L. were grown at ambient (35.5 Pa) and elevated (120 Pa) CO2 for 46 d. Initially, the rate of photosynthesis (N-P) was 90% higher under elevate d CO2 in the green sectors of both HV and HG plants. After 32 d of exposure to high CO2, PN Of HG at high CO2 had dropped to that of the ambient CO2 g rown plants, while the PN Of HV plants remained 48% higher at elevated than at ambient CO2. V-cmax (maximum rate of carboxylation) and J(max) (maximum rate of potential electron transport) of both HV and HG decreased with tim e at elevated but not at ambient CO2 These reductions were less for HV than for HG. Elevated CO2 increased the relative growth rate (RGR) of the KV bu t not of the HG plants. The results suggest that leaf variegation may moder ate photosynthetic acclimation to elevated CO2, a phenomenon that could be of considerable significance to selection of species for cultivation under conditions of high CO2.