Pollinium structure in periplocoideae (apocynaceae)

Abstract

The pollinium morphology of ten genera (Atherolepis Hook, f., Decalepis Wight & Arn.[=Baeolepis Decne., Janakia J. Joseph & V. Chandras.], Finlaysonia Wall., Gongylosperma King & Gamble, Gymnanthera R. Br., Hemidesmus R. Br., Meladerma Kerr, Stelmacrypton Baill., Streptocaulon Wight & Arn., Utleria Bedd. ex Benth. & Hook, f.) and Raphionacme abyssinica Chiov. of the Periplocoideae have been examined and compared with Cynanchum ellipticum (Asclepiadoideae) using light‐, scanning‐and transmission electron microscopy. In the Periplocoideae four free pollinia are produced in each anther. The pollinia are not attached to a translator while in the anther. However, by anthesis the pollinia are deposited on the spoon of the translator. The pollinium is not covered by a pollinium wall (ectexine). The pollinium consists of loosely agglutinated, but not fused, tetrads. The only physical connection between the tetrads was observed when two pores, of adjacent tetrads, are opposite one other. In such cases the tectum and granular stratum of the adjoining tetrads may be fused. The wall structure of the tetrads forming the pollinium consists of a tectum and a granular stratum subtended by an intine.