A 2.0 um maize leaf section illustrating the immunolocalization of the enzyme ribulose bisphosphate carboxylase (rubisco) in the chloroplasts of the bundle sheath cells surrounding the vascular bundles. Maize is a C4 plant and, as a result, spatially segregates components of the photosynthetic process between the leaf mesophyll and the bundle sheath. Rubisco was localized using a rabbit anti-rubisco antibody and visualized using the highly cross-adsorbed Alexa Fluor 488 goat anti–rabbit IgG antibody (Cat. no. A11034). The remaining fluorescence is due to the autofluorescence of chlorophyll, which appears red and is localized to the mesophyll plastids; lignin, which appears dull green and is localized to the xylem of the vascular bundle; and cutin, which appears bright green and is localized to the cuticle outside the epidermis. Image contributed by Todd Jones, DuPont.