Sporoderm ultrastructure and development in Aristolochia manshuriensis Komarov (Aristolochiaceae)

Abstract

Pollen ontogeny and sporoderm development in Aristolochia manshuriensis were studied for elaboration of the inaperturete pollen ontogeny in Aristolochia. Despite the formation of apertures in the tetrad period, the sporoderm in A. manshuriensis becomes inaperturate at the end of the free microspore period. A similar immature exine is also detected in A. macrophylla. Variants of aperture formation in the tetrad period in A. manshuriensis or formation of a polar aperture in the free microspore period in A. clematitis are associated with types of microsporogenesis. The ectexine and endexine in A. manshuriensis are formed over a longer time and reached much greater thickness than those in A. clematitis. The endexine and intine in A. manshuriensis do not reach a mature state, similar to A. clematitis. The exine of A. manshuriensis cracks, releasing a pollen tube enveloped by the intine. This fact does not hinder the functioning of the male gametophyte of A. manshuriensis.