Ormosia microphylla is a rare and endangered tree species endemic to China and is listed as a Class I nationally protected wild plant. It possesses high economic and ecological value. Due to limited seed sources, traditional seed propagation methods have a low propagation coefficient; therefore, tissue culture technology has become an important approach for the rapid propagation of O. microphylla. This study aimed to establish an in vitro rapid propagation system for O. microphylla.

Mature seeds of O. microphylla were used to establish an aseptic seedling culture system, and the optimal seed sterilization protocol was screened. Bud-bearing stem segments from germinated aseptic seedlings were used as explants, and an L₉(3³) orthogonal experimental design was employed to determine the optimal medium for shoot induction and proliferation. The effects of different subculture cycles on proliferation were analyzed during the subculture stage. Finally, rooting and transplanting experiments were conducted to screen for the optimal rooting medium and the most suitable transplanting substrate.

The optimal sterilization protocol was to retain the seed coat and disinfect the seeds with 2% NaClO for 12 min, under which no contamination occurred, with an aseptic seedling rate of 70.37% and a browning rate of 23.23%. The optimal proliferation medium was MS supplemented with 1.5 mg·L^-1 6-BA and 0.15 mg·L^-1 IAA, yielding a proliferation coefficient of 5.23 and an average shoot height of 3.59 cm. The third subculture cycle showed the best proliferation performance, with a proliferation coefficient of 5.33. The optimal rooting medium was 1/2 MS supplemented with 0.3 mg·L^-1 NAA, resulting in a rooting rate of 93.33%, an average of 3.95 roots per shoot, and an average root length of 3.63 cm. The highest survival rate (95.56%) was achieved when vermiculite∶perlite (1∶1) was used as the substrate.

This study established a relatively stable and efficient in vitro rapid propagation system for O. microphylla. Based on experimental investigations of key procedures including explant sterilization, bud induction and proliferation, subculture, rooting and acclimatization, this work provides a theoretical basis and technical support for the germplasm conservation and large-scale propagation of this species.

The Ormosia hosiei is a unique and precious native wood species in China, which is listed as a key protected wild plant. This study aims to investigate the effects of inoculating different rhizobia on the growth and physiological indicators of O. hosiei seedlings, to reveal the growth-promoting effects of different rhizobia on O. hosiei seedlings and screen out efficient rhizobial strains for cultivating strong seedlings of O. hosiei.

O. hosiei seedlings were inoculated using eight rhizobial strains, and the effects of rhizobial inoculation on growth traits, nodulation status, leaf nitrate reductase activity, leaf nitrate nitrogen content, chlorophyll content, photosynthetic rate, and other indicators were analyzed. The seedling quality was evaluated by using a principal component comprehensive evaluation.

The growth and physiological performance of O. hosiei seedlings inoculated with rhizobia were superior to those of seedlings without inoculation. Compared with the seedlings without inoculation, the increases in height, ground diameter, and total biomass of the seedlings inoculated with rhizobia were 25.75%-96.49%, 17.31%-51.16%, and 42.11%-102.63%, respectively. The increases in total root length, total root surface area, average root diameter, and total root volume were 14.88%-201.33%, 17.56%-169.76%, 2.38%-23.81%, and 40.98%-190.16%, respectively. The increases in chlorophyll content, net photosynthetic rate, transpiration rate, nitrate reductase activity, and nitrate nitrogen content were 2.14%-66.31%, 27.36%-209.43%, 71.88%-337.50%, 31.30%-191.60%, and 2.33%-48.84%, respectively. The order of comprehensive quality scores of O. hosiei seedlings inoculated with different rhizobial strains was: No.5 > No.6 > No.4 > No.8 > No.2 > No.7 > No.1 > No.3.

Inoculation with rhizobia could significantly improve the physiological status of O. hosiei seedlings and promote their growth and biomass accumulation. Among them, strains No. 4, No. 5 and No. 6 have better growth-promoting effects and could be used as excellent strains for cultivating strong seedlings of O. hosiei.