Examples of tissue sections where in situ PCR was unsuccessful. Inconsistent, non-uniform expression of 18S rRNA in Vitis vinifera leaf (A) and Hordeum vulgare leaf (B). Severely damaged Glycine max root cells (C). Distinct staining of cell nuclei (genomic DNA) in Triticum durum root section (D). Fluorescent staining using Elf97 in Hordeum vulgare leaf (E, Hv18S rRNA and F, Hv18S rRNA negative control; Zeiss stereofluorescence microscope) and Triticum durum root sections (G, TmHKT1; 5-A and H, TmHKT1;5-A negative control; Nikon confocal microscope). Please see Table 5 for troubleshooting tips. Scale bars represent 100 μm.