Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomo- und anemophilen Angiospermen: Polygonaceae

Abstract

Polygonum bistorta, Fagopyrum esculentum (both entomophilous), Rheum rhabarbarum and Rumex scutatus (both anemophilous) (Polygonaceae) are studied in relation to pollenkitt (amount, structure, distribution on the exine) and to the exine itself (sculpturing, intrasexinous caves, bacula, tectum). In Polygonum bistorta the large quantity of the homogeneous, electron-dense pollenkitt is deposited in the rather small intrasexinous caves, but also as homogeneous droplets at the nearly closed tectum with the essentially smooth surface. F. esculentum produces an inhomogeneous, less electron-dense and above all rather small quantity of pollenkitt; the pollenkitt is deposited favourably in the caves of the reticulate exine, but also at the tectum. Compared to F. esculentum, Rheum rhabarbarum produces a large, but very inhomogeneous quantity of pollenkitt. The pollenkitt is deposited very heterogenously at the pollen grains. Moreover, the pollenkitt is deposited mostly in the intrasexinous caves, and only some electronlucent droplets adhere at the tectum. The small quantity of the very inhomogeneous pollenkitt of Rumex scutatus can be observed as predominantly electron-dense mass in the tall intrasexinous caves, while only small fibrous quantities of pollenkitt adhere at the rather rough tectum-surface. These findings indicate that the changes from entomo- to anemophily in the pollination mode of Angiosperms are accompanied by step-wise changes of the correlated character syndroms. These character syndroms do not affect only the flowers, but also the pollen grains in relation to the fine structure of the exine and pollenkitt.