Pollen Size and Variability as Related to Chromosome Number and Speciation in the Genus Camellia

Abstract

Pollen size and chromosome numbers were correlated in species of Camellia. The presence of unreduced pollen complicated some correlations. Speciation was an impor-tant influence on pollen size. Pollen size was more closely related to chrornosome number among species within subgeneric sections than between species of different sections. The closest correlations were observed among individuals of different chro-mosome numbers of the same species. Species represented by native forms from the wild generally had smaller pollen of more unifcrm size and shapet han species repre-sented by cultivars that were the products of cerituries of intense cultivation, breeding, and selection. Higrhly developed cultivars were more likely subjected to introgression and hybridization and were probably more highly heterozygous than their wild relatives. Species with highly variable pollen or low percentages of good pollen have in many cases also been described in the literature as of probable hybrid origin. Thus, it appe-ared that studies of pollen size, range in pollen diameter, and percentage of good pollen could serve as an indicator of hybridity among Camellia species.