Occurrence and significance of polysomaty in species of Mimosa L

Abstract

Polysomaty is the occurrence of cells with different ploidy levels in the same organ or tissue and there are records of this in root-tip cells of some Mimosa species. The objective of the present work was to verify the occurrence, possible cause and significance of polysomaty in a range of species of this genus. In root-tip cells of 68 accessions of 43 diploid and tetraploid Mimosa species, the percentage of polysomatic cells ranged from 5% to 87%. Pretreatment with the antimitotic paradichlorobenzene did not cause polysomaty but increased it in some accessions. When relating seedling root size and percentage of polysomatic cells, for most of the species a higher percentage of polysomatic cells was found in roots from 6 to 10 cm length. For M. scabrella ("bracatinga"), a comparative analysis of seedling root-tip cells and roottip cells from well-developed plants kept in pots in a greenhouse showed that polysomaty occurred only in the seedling root-tips. The data suggest that, in Mimosa, polysomaty occurs only for a short period of the seedling development, probably as a natural mechanism to accelerate its development and establishment. © 2012 Dipartimento di Biologia Evoluzionistica, Università di Firenze.