The relationship between chloroplast number and genome size in Zea mays ssp. mays

Fifteen maize populations were analyzed with respect to their genome size and chloroplast number per guard cell. The reported genome sizes of these populations range from 9.82 pg to 13.8 pg. When all the populations were analyzed, a positive correlation between genome size and chloroplast number was observed. Upon removal of two of the populations from the analyses, a significant positive correlation was observed with an r value of 0.72. These results are consistent with published data which demonstrate a positive correlation between interspecific genome size and chloroplast number. Genome size does appear to influence the number of chloroplasts per guard cell within the species Zea mays ssp. mays. Two of the populations have chloroplast numbers indicative of large genome size, yet have small genome sizes. In these populations, genetic factors appear to regulate chloroplast number per guard cell. Nucleotypic factors, in addition to genetic factors, should be included in those mechanisms which regulate chloroplast number within as well as among species.