Euphyllophytes comprise ferns

gymnosperms

and angiosperms. Relatively abundant chloroplast genome sequence data has been available for them. In this research

chloroplast gene sequences of 29 euphyllophyte species were extracted from their completely sequenced chloroplast genomes; then an adaptive evolutionary analysis was performed on the chloroplast genes by running PAML under models allowing ω (nonsynonymous/synonymous rate ratio) to vary among sites. The results showed that:①The percentage of chloroplast genes under positive selection in ferns

gymnosperms

and angiosperms were 6.5%、7.5% and 19.2%

respectively. The number of positively selected genes in angiosperms appeared significantly larger than that of ferns and gymnosperms.②Most positively selected genes were genetic system or photosynthesisrelated genes. Their coding proteins often functioned in chloroplast protein synthesis

gene transcription

energy transformation and regulation

and photosynthesis. We infer that the chloroplast functional genes may have played key roles during the adaptation of euphyllophytes to terrestrial ecosystems.