In situ PCR for various transcripts in barley and Arabidopsis. Blue staining demonstrates presence of cDNA (left panel) while a brown colour indicates absence of amplified target cDNA within cells (right panel). (A, left) 18S ribosomal RNA positive control to show staining in all cell-types of barley leaf, (B, left) 18S ribosomal RNA positive control to show staining in all cell-types of Arabidopsis leaf, (C, left) AtCAX1 expression predominantly in the mesophyll of Arabidopsis leaf, (D, left) guard cell staining of a barley Aluminum-activated malate transporter (ALMT) (SL1251) from an in situ PCR performed on epidermal peels. (E and F, left) detection of an Arabidopsis ALMT14 in the septum (E) and embryo (F) of developing flowers/siliques. The same primers and conditions were used for the corresponding negative controls (A-F, right panels, Table 6). Scale bars represent 100 μm.