Pollen Ontogeny in Catananche caerulea L. (Compositae: Lactuceae) I. Premeiotic Phase to Establishment of Tetrads

Abstract

The SEM has been used to observe microsporogenesis in Catananche caerulea (Compositae: Lactuceae) from the time of mother cell formation to the early tetrad stage. The three main ontogenetic features discussed are: intercellular cytoplasmic connections between meiocytes, the deposition of the callose special cell wall and changes in cytoplasmic organelles that are associated with the cycle of ribosome elimination occurring during the transition to the gametophyte generation. The results are compared with other flowering plants and with members of tribe Lactuceae that have morphologically different mature pollen grains.