Relative exon and intron lengths of chloroplast APx in Arabidopsis thaliana (At), Selaginella moellendorffii (Sm), Physcomitrella patens (Pp) and Chlamydomonas reinhardtii (Cr). tAPx are shown in red, sAPX in black. The vertical lines connect corresponding splice sites. The numbers represent positions of corresponding amino acids in the alignment shown in fig. 1A and the relative splice sites within the corresponding codon.