COMMENTS

The focus in this discussion has been primarily on knowledge gained about plastid chromosomes and genes from analyses of the maize chloroplast chromosome and its genes.Other work on plastid molecular biology，including the sequencing of genes，has been carried out in a number of laboratories with chloroplast DNA of spinach，Nicotiana，pea，wheat，Chlamydomonas，Euglena，and other species.It is beyond the scope of this limited discussion to include all of these items although some data from such studies appear in Table 1.

Currently available information on plastid chromosomes and genes will guide future analyses of chloroplast chromosomes and investigations of mechanisms for the control of plastid gene expression and the integration of expression of plastid and nuclear genes.Furthermore，the protein products of severa lof the genes that have been cloned and sequenced are of great interest for understanding mechanisms of photosynthesis；this knowledge remains to be exploited to broaden our understanding of this process.(https://www.daowen.com)