Ca-bound pectin was plentiful in the boundary cell layers between the skin and mesocarp.

<p>A, Ca content in tomato fruit tissues. B, Ca content in the tomato fruit cell wall. The alcohol-insoluble residue fraction was extracted from fruit tissues for analysis. Ca content in each fraction was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). C, Ca determination between the skin and mesocarp. Quantitative imaging by secondary ion-microprobe mass spectrometry (SIMS). Ruthenium: showing ruthenium, which binds with pectin. Calcium: showing calcium content. Merge: showing overlap of ruthenium (pectin) and calcium.