Immunogold localization of callose in control and chilled (4 h, 28 h) leaves of the CM 109 maize inbred line (CS): (A, B) negative control; no immunogold labelling when primary antibody was omitted; (C, E, G) KMS/BS interface; (D, F and H) BS/VP interface. Note some callose labelling in cell wall close to the plasmodesma region in control leaves (C, D) and those chilled for 4 h (E, F). Note strong callose labelling near the plasmodesmata in leaves chilled for 28 h (G, H). Abbreviations: CS, chilling-sensitive line; KMS, Kranz mesophyll; BS, bundle sheath; VP, vascular parenchyma; CW, cell wall; ER, endoplasmic reticulum; Pd, plasmodesmata. Scale bar = 100 nm.