Effect of Ploidy Level on Growth, Differentiation, and Morphology in Physcomitrella patens

Abstract

Abstract Due to its high rate of homologous recombination, the moss Physcomitrella patens (Hedw.) B.S.G. is used as a novel system to facilitate gene/function-analyses. Loss-of-function mutations are easy to identify in the moss, as the dominant phase is the haploid gametophyte. Regenerating protoplasts were used to establish different moss lines with ploidy levels of 1C, 2C, and 4C. Flowcytometric analysis of three haploid, three diploid, and two tetraploid Physcomitrella lines revealed that haploid and diploid lines were cytologically stable, whereas nuclei of tetraploid lines exhibited varying DNA-contents. The effect of polyploidization on the phenotype, growth, and differentiation of Physcomitrella was investigated in vitro. The growth of three haploid, three diploid, and two tetraploid genotypes was evaluated after four weeks of axenic culture. The effect of the genotype on the growth rate of plants cultured on minimal medium was statistically significant; in contrast the ploidy level had no effect....