Flowering Dynamics, Pollen Viability and Stigma Receptivity of Nai Plum (Prunus salicina Lindl. var. cordata) from Different Provenances

Nai plum (Prunus salicina Lindl. var. cordata) is a high-value fruit crop in southern China, yet its post-harvest quality is often compromised by fruit browning, a major constraint to storage and marketability. Addressing this challenge requires a deeper understanding of the species’ reproductive biology, which underpins both fruit set and cultivar improvement. In this study, we characterized the flowering biological characteristics of Nai plum accessions introduced from Yanling and Liuyang (Hunan Province) and Shaoguan and Lechang (Guangdong Province). Using field observations combined with microscopic and submicroscopic techniques, we documented flowering phenology, flowering dynamics, floral organ traits, pollen viability and stigma receptivity. The flowering period was in March, lasting 26–28 d, and the group blooming period was divided into three stages: Initial opening stage, Full blooming stage, and Final flowering stage. The single-flower opening process was divided into eight stages. Pollen viability followed a unimodal curve, peaking at the petal flattening stage (PF) across all accessions, though peak values varied by provenances. Stigmas were of the wet type, with receptivity following a weak–strong–weak pattern; peak receptivity occurred at early flowering (EF) and PF in most accessions. The EF of Nai plum from Yangling (S1) lasted for 7 h, and PF lasts for 28 h. The EF of Nai plum from Yangling (S2) lasted for 3 h, and the PF lasted for 11 h. Both the EF and the PF of Nai plum from Shaoguan (S3) lasted for 14 h. The bud white stage (BW) of Nai plum from Lechang (S4) lasted for 6 h and the EF lasted for 7 h. The EF of Nai plum from Liuyang (S5) lasts for 7 h, and the PF lasted for 28 h. These findings clarify the reproductive phenology and floral biology of Nai plum, providing foundational knowledge that can inform breeding strategies and cultivation practices aimed at improving fruit set and, ultimately, post-harvest quality.