Variability and bimodal distribution of size in uninuclear microspores of Aesculus flava Marshall

Aesculus flava (syn. A. octandra) is a species of buckeye native to eastern North America, from Pennsylvania, west to eastern Illinois, and south to the northernmost parts of Alabama and Georgia. Pollen dimorphism has been detected in anthers of some woody species. Uninuclear microspores isolated from closed flower buds in horse chestnut (R a d o j e v i c , 1989, 1991; C a l i c et al., 2003/4) and red chestnut (M a r i n k o v i c and R a d o j e v i c , 1992) showed differences in size, shape, staining intensity, fluorescence, viability, and embryogenic potential (R a d o j e v i c et al., 2000). Moreover, pollen orginating from 13 species of the genus Aesculus showed differences in size and shape, pore position, sculpturing of the colpal membrane, and sculpturing of the mesocolpia (P o z h i d a e v, 1995). The small yellow-green inflorescence of Aesculus flava is about 17 cm long and 7 cm wide. Composed of an upright panicle of many solitary flowers, it appears in mid-May, the inflorescence clearly rising above the expanded foliage. As in flowers of Aesculus hippocastanum, A. flava flowers located in the basal part of the panicle are female and fertile, while flowers in the middle are bisexual and those on the top are male (H e y w o o d , 1978).