Microscopy images of chloroplast protrusions (CPs) in leaves of R
anunculus glacialis. Whole individuals were irradiated (PPFD 1600 μmol photons·m−2·s−1) and simultaneously exposed to different gas mixtures, characterized by certain CO2/O2 ratios. (a) light microscopy image (DIC illumination) of palisade cells treated with gas mixture 1 (50 ppm CO2/21% O2). Arrows indicate CPs, horizontal bar: 10 μm. (b) DIC image of a single palisade parenchyma cell treated with gas mixture 4 (370 ppm CO2/21% O2). horizontal bar: 10 μm. (c) schematic drawing of the same cell, blue stars indicate CPs. (d) transmission electron microscopy (TEM) image of a single palisade parenchyma cell (gas mixture 3: 2000 ppm CO2/2% O2). Ch, chloroplast; ER, rough endoplasmic reticulum; G, golgi stacks; M, mitochondria; P, peroxisome; pl, plastoglobuli; photosynthetically active photon flux density. arrow, chloroplast protrusion; horizontal bar: 1 μm.