Seed Germination of Huagaimu, a Critically Endangered Plant Endemic to Southeastern Yunnan, China

Abstract

As a critically endangered tree in the Magnoliaceae family, huagaimu (Manglietiastrum sinicum) is represented by only 10 mature individuals in evergreen broadleaved montane forests of southeastern Yunnan Province, China. Our previous work revealed the existence of a seed dormancy period for this species. The current study was performed to evaluate the effects of plant growth regulators (PGRs) and moist chilling on breaking seed dormancy in this species. Germination of seeds pretreated for 24 h with gibberellic acid (GA3), α-naphthaleneacetic acid, 6-benzyladenine, and 2,4-dichlorophenoxyacetic acid indicated that only GA3, at concentrations of 300 and 500 mg·L−1, can significantly break the seed dormancy of huagaimu after 50 days of incubation, with about 66% germination under 500 mg·L−1 GA3. Moist chilling at 4 °C for 3 weeks can also effectively break the seed dormancy of the species, with 56% of seeds treated in this way germinating after 30 days of incubation. The combined treatments of PGRs followed by moist chilling were also conducted. Based on germination results after 30 days of incubation, the seed germination of combined treatments was significantly higher than that of PGR treatments. However, the seeds treated only with moist chilling presented the highest germination percentage among all the treatments.