The impact of long-term CO2 enrichment on sun and shade needles of Norway spruce (Picea abies): Photosynthetic performance, needle anatomy and phenolics accumulation

► Complex study of conifer photosynthetic apparatus and phenolics content was performed. ► Long-term elevated [CO2] enhanced photosynthetic rate in Norway spruce. ► Mesophyll structure was estimated using confocal microscopy and stereology. ► Elevated [CO2] did not affect either mesophyll structure or phenolics accumulation. ► Needle differentiation and phenolics content is principally driven by irradiance.