Anther development and pollen fertility in a polyploid cultivar of <i>Platanus</i> × <i>acerifolia</i> Willd. 'Huanong Panlong'

Platanus, a key species in urban landscaping, is a classic allopolyploid with three distinct subgenomes. Polyploidization often induces meiotic irregularities, offering promising opportunities for breeding improved ornamental cultivars with suppressed flowering and fruiting. Here, we investigated the morphological and cytological characteristics of synthetic polyploid <italic>P.</italic> × <italic>acerifolia</italic> 'Huanong Panlong' (HP, 2n = 12x = 84) induced via colchicine treatment, and demonstrated that its higher ploidy level correlates with significantly reduced pollen viability (9.54%). Microstructural analysis revealed that no structural abnormalities were detected in the sporophytic anther tissues of 'HP'. However, cytological analysis identified a series of meiotic abnormalities during the microsporogenesis, including chromatin stickiness, multivalent formation, persistent chromatin bridges, and disordered chromosome segregation, resulting in dyad, triad, and polyad formation. Notably, approximately 72.27% of meiocytes exhibited abnormal tetrad formation. These meiotic irregularities likely account for both the observed pollen sterility and the consequent reductions in fruit set (3-6 cones an adult tree) and seed germination rate (6.85%). From an applied perspective, the observed reproductive deficiencies hold particular significance for urban horticulture, as both <italic>P.</italic> × <italic>acerifolia</italic> pollen grains and achene fibers are potent respiratory aeroallergens.