Pollen morphology and its phylogenetic implications in the genus Picea

Pollen grains from 20 spruce species were examined using scanning electron microscopy, to study the phylogeny of pollen morphology in spruce. Morphological characteristics of the pollen were examined among different species based on statistical data and photographic observation. The mean pollen size of 20 spruce species ranged from 84.327 to 118.793.18 μm. Based on morphological photography, two zygomorphic bladders were distributed on the underside of the corpus and were found at the edge of the cap near the corpus surface. The bladder’s surface texture was smooth and had no distinct variations among species. Germinal furrows formed clear striates between the two bladders. According to clustering analysis, 20 spruce species were classified into three sections, namely, Castict, Schrenkiana and Picea, and the Picea section was classified into two subsections, Jezonensis and Picea. Corpus veins experienced notable differentiation among sections, and their evolutionary trend progressed through sections Castict, Schrenkiana and Picea. Within subsection Picea, parallel evolution occurred between the two subsections.