Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomo- und anemophilen Angiospermen: Salicaceae, Tiliaceae und Ericaceae

Abstract

The characteristics of pollen cementing (stickiness; total amount, structure and distribution of the pollenkitt; fine structure of the exine) have been studied in Salix caprea, Populus nigra and P. tremula (Salicaceae), Tilia platyphyllos and T. tomentosa (Tiliaceae) , and Erica herbacea, Calluna vulgaris and Andromeda japonica (Ericaceae) . The homogeneous, electron-dense pollenkitt of S. caprea fills up the interbacular caves completely and is also situated on the outside layer of the exine; so the pollen is sticky and insectpollination is dominating. In contrast the also homogeneous, mostly electron-dense pollenkitt of P. nigra and P. tremula remains largely in the loculus, while only a little moves to the exine caves; the tectum is free of pollenkitt; so the pollen is powdery and the result is pollination by wind. In T. tomentosa and T. platyphyllos the mostly electron-dense (in part also foamy) pollenkitt is located preferably in the caves, but also in small amounts on the outer layer of the exine; so the pollen is only of medium stickiness, and pollination by insects and by wind is possible. In E. herbacea, C. vulgaris and A. japonica there is no pollenkitt sensu stricto at all: in the loculus tapetum-borne irregular globuli do not adhere on the exine; their nature remains obscure; there are no viscin-threads at all. Because of the “Streukegel”-mechanism the powdery pollen of the described Ericaceae allows pollination by wind.