Fig. 5From: Chloroplast gene expression level is negatively correlated with evolutionary rates and selective pressure while positively with codon usage bias in Ophioglossum vulgatum LHeat map of the correlation between codon usage bias and gene expression level (56 filtered genes). Effective number of codons (ENC); the tRNA adaptation index (tAI). The numbers on the upper triangular are correlation values (Spearman’s rank correlation coefficient). * represents significant at the 0.05 levelBack to article page