作 者 ：Zhang Yu-Long, Chen Yi-Ling
期 刊 ：植物分类学报 1992年 1期
Keywords:Pollen morphology, Rhamneae,
Abstract:
Pollen morphology of 25 Chinese species, representing 6 five genera in the tribe
Rhamneae of Rhamnaceae, was examined under LM and SEM. Pollen grains are
subspheroidal or suboblate, obtuse-triangular in polar view, 3-colporate, with the polar axis
(P)10.4-28.7μm long and equatorial axis (E) 11.3-30.5μm long, P/E = 0.81-1.11. Colpi
generally narrow and long, ora lalongate, with two ends connected with the thinned part of
exine, forming a H-shape. Four thickenings were observed where colpi and ora cross, but
sometimes the thickenings were indistinct or formed a ring. The stratification indistinct. The
ornamentation of exine obscure or indistinctly reticulate under LM, but rugulose,
short-striate, rugulose-foveolate or reticulate under SEM.
The exine ultrastructure of Rhamnus ussuriensis was examined under TEM. It consists of
imperforate tectum, granular layer, foot layer and endexine. The tectum is rather thick with
uneven surface, while the granular layer is rather thin.
A key to the genera based on pollen characteristics is provided and the general
pollenmorphology of five genera, i.e. Sageretia, Rhamnus, Hovenia, Colubrina and Alphitonia,
is described respectively.
Based on pollen size, the four thickenings and the ornamentation, the five genera under
study may be distinguished from each other. For example, pollen grains are smaller in
Sageretia; the four thickenings are larger and distinct in Hovenia and Alphitonia. However,
the ornamentation is short-striate under SEM in Hovenia and Alphitonia, while reticulate in
the Colubrina and Rhamnus ( Subgen. Rhamnus) .Two different concepts of Rhamnus exist
among taxonomists. Heppeler and Suessenguth divided Rhamnus into two subgenera
(Subgen. Frangula and Subgen. Rhamnus), whereas Grubov separated Subgen. Frangula
from Rhamnus as an independent genus. According to the pollen morphology, the separation
is reasonable.