Pollen Morphology of Primula (Primulaceae) in Japan and Its Systematic Implications

Abstract

Pollen grains from nine of the fourteen Primula species (Primulaceae) native to Japan were observed by scanning electron microscopy (SEM). Among these, pollen morphological features of seven species were examined by SEM for the first time, and the wall structure of two species by transmission electron microscopy (TEM) as well. The Japanese Primula species were comparatively stenopalynous in having 3(–4)-parasyncolporoidate with microreticulate sculpture except for 3-colporoidate pollen in P. japonica of section Prolifera. A variation in pollen morphology was found among the investigated species, particularly in size and shape of the triangular apocolpial fields (polar area). Both P. modesta var. fauriei and P. sorachiana constituting section Aleuritia showed small pollen grains with small apocolpial fields, which indicate an intermediate state between parasyncolporoidate and syncolporoidate apertures. Apocolpial field connection with the adjoining exine surface that was sometimes found in P. nipponica pollen might show an intermediate state between parasyncolporoidate and colporoidate apertures.