Variation and plasticity of photosynthesis and respiration in local populations of fat‐hen Chenopodium album in northern Japan

Abstract

AbstractTo examine variation and plasticity of photosynthesis and dark respiration among regional populations, seven populations of Chenopodium album L. (a shade‐avoider species) were collected in northern Japan and grown under shaded and unshaded conditions. The light‐saturated photosynthetic rates (Pmax) on both a leaf area and a mass basis significantly differed among the populations; the light regime affected Pmax per leaf area, but had no effect on Pmax per leaf mass. There were no significant differences among the populations in dark respiration rates (Rd) either per leaf area or mass; the light regime affected Rd per leaf area, but had no effect on Rd per leaf mass. Specific leaf area (SLA) exhibited significant differences among populations and SLA significantly increased under shaded conditions. None of these traits showed clinal variation along a latitudinal gradient, partially because the climatic span across which the populations were collected was relatively small (13.9–18.9°C). Pmax, SLA and α (initial slope at zero irradiance of the light‐photosynthetic rate relationship curve) showed great genetic variation, whereas Rd showed little genetic variation. Pmax and Rd showed high plasticity on a leaf area basis, but not on a leaf mass basis as SLA and α had high plasticity. We found that there is great genetic variation between local populations of C. album within a small geographical range, which controlled plasticity of the reaction norm of the photosynthetic property for the light regime during the growth period. More variation in reaction norms would enable C. album populations to colonize unpredictable habitats. Genetic variation after long‐term adaptation to habitat conditions as well as plasticity during short‐term acclimation to an unpredictable environment could enable C. album to distribute itself successfully over a wide range of climates.