The subfamily Fumarioideae is the most diversified group of the Papaveraceae family, a eurypalinous group whose pollen information has classically been used for studying systematic issues. In this paper we present a study of pollen morphology and development of the pollen wall in most of the Fumarioideae genera excluding Hypecoum. We describe a high variability in pollen grain ornamentation and in aperture shape and number among genera of the subfamily. Remarkable features of the pollen-wall layer development in Fumarioideae are a lamellated foot layer at the young microspore stage and a granular infratectum. In the apertures, the aperture membrane formed by ectexine is absent for the subtribe Fumariinae, and the ultrastructure of the exinous oncus shows that the endexine is arranged in three different ways among the Fumarioideae representatives. From vacuolate microspore stage onward the apertures of most Fumarioideae genera are covered by a fluffy plug, while during young bicellular stage the intine under the apertures develops from the material that accumulated in the periplasmic space. We have identified significant differences between the pollen features of the tribe Fumarieae and the tribe Hypecoeae, such as psilate exine and granular infratectum. The presence of atypical pollen features in Fumarioideae is discussed within the framework of current knowledge of pollen wall development, highlighting their implications for a better understanding of pollen wall evolution.
Keywords: Fumarioideae, Papaveraceae, Aperture, Pollen morphology, Pollen wall, Ultrastructure