Some known porate pollen germinal apertures are actually pororate: Observation based on a study from eastern Himalaya

Abstract

In today's pollen morphological studies, distinction between the two aperture types, namely, porate and pororate is obscured by generalised use of the former in defining a more or less isodiametric aperture. Present study points out the precise dimensional differences and incongruence between the ecto and endoapertures (representing pore and ora respectively) which in turn dictates the true apertural nature, whether it is ‘porate’ or ‘pororate’. In this work, pollen morphology of 10 eastern Himalayan species were studied; among them six species hitherto known for having porate condition (simple aperturate) are actually found pororate (compound aperturate) in nature. We also observed pororate condition in Symplocaceae which was known to have either porate or colporate pollens till date. Therefore, pororate aperture is now found in Cannabaceae, Urticaceae and Symplocaceae. Occurrence this apertural condition in the nine studied species reflects their most advanced/climax stage of aperture evolution. Thus, our observation deviates considerably from available information on pollen apertures of the studied plant families and consequent change in the systematic and phylogenetic interpretation of the studied species is suggested.