Chloroplast Numbers per Cell and Cell Volumes in Apomictic Hieracium Polyploids (Asteraceae)

Abstract

As is well known, chloroplast numbers per guard cell of stomata and guard-cell sizes are increased in tetraploids as compared with diploids, and this increase is found to be smaller in tetraploids from nature (“aged” polyploids) than in induced (“young”) tetraploids. This evolutionary reduction did not occur in apomictic tetraploid Hieracium species from nature. Hence, the evolutionary reduction of chloroplast-number increases and probably also of cell-size increases in amphimictic tetraploids is not the result of physiological long-term regulation, which should have occurred in apomictic Hieracium as well, but of selection.-Four pentaploid or hexaploid strains of Hieracium subgenus Pilosella showed chloroplast numbers as if the plants were only about triploid; possible reasons for this are discussed.