Cell Sizes and Chloroplast Numbers per Cell of Hemiploid and Polyploid Plants

Abstract

Whereas guard cells of stomata of induced polyploids in the C₀ generation show on average more than twice the volume of diploids, the volume is reduced in hemiploids to less than one half when compared with normaploid plants. The shortage cannot be explained as the result of an unspecific disorder of newly induced heteroploids because hemiploids and polyploids show opposite effects. Since the surplus disappears in later generations, both surplus and shortage might be overshoots on the way to new steady states. The chloroplast numbers of mature guard cells do not show such an effect; they therefore do not depend mainly on cell size. Rather, both characters depend on ploidy. Further evidence is discussed. In a double-logarithmic grid, chloroplast numbers and cell volumes in C₀ generation are correlated linearly with ploidy, showing different slopes. Since nuclear and chloroplast DNA cooperate in the synthesis of many chloroplast proteins-and most envelope proteins are encoded in the nucleus-the nuclear DNA amount is coupled with the growth and division of plastids. Thus the continuity of plastids may result.