Air-Layering Propagation of the Nationally Protected Plant Ormosia purpureiflora Succeeds

Researchers from the Management Office of Guangdong Luofushan Provincial Nature Reserve, South China Botanical Garden (SCBG), the Chinese Academy of Sciences and Guangzhou Linfang Ecological Technology Co., Ltd., have achieved an important success in propagating the nationally protected plant Ormosia purpureiflora by air-layering technology.

The genus Ormosia belongs to the legume family (Fabaceae). There are approximately 130 species worldwide, distributed across the tropical and subtropical regions of Asia, Australia, the Americas and Africa. The genus exhibits a distinctive Asia–America disjunct pattern, which is of great significance for understanding the origin and evolution of plants. China has about 37 Ormosia species, and in 2021, all species of this genus were listed as nationally key-protected wild plants. Guangdong Province is a main distribution area of the genus, with 17 recorded species. Among them, O. purpureiflora,O. boluoensis and O. ferruginea are endemic to the province.

Ormosia purpureiflora is a critically endangered species. It has so far been found only in Guangdong Luofushan Provincial Nature Reserve (LFS Reserve) and Guangdong Longmen Nankunshan Provincial Nature Reserve (NKS Reserve). After years of field investigation, it is revealed that its actual distribution area lies between 113°49′–114°2′ E and 23°15′–23°38′ N, spanning 13′ of longitude and 23′ of latitude, representing a very narrow range. Ormosia purpureiflora grows at elevations of 400–720 m, with the lowest locality in the LFS Reserve and the highest in the NKS Reserve. The species is scattered and disjunctly distributed in the reserves, and within different sites, the number of individuals varies greatly. The NKS Reserve records about 200 individuals in total. Within LFS Reserve, several sub-populations are located on different mountain bodies, with the population size ranging from 30 to 1,000 individuals and totaling approximately 1,944.

In the wild, O. purpureiflora individuals tend to flower only once every few years. Seeds, therefore, are not produced every year. During flowering and fruiting periods, the flowers and fruits of O. purpureiflora are vulnerable to pests and diseases, resulting in a low yield of healthy seeds. Once mature, their seeds have poor dispersal and propagation capabilities, and the hard, thick seed coats hinder germination. In addition, the seedlings grow slowly and are also susceptible to pests and diseases with low competitiveness. These result in slow natural regeneration and small populations of O. purpureiflora. Currently, ongoing climate change has exacerbated the threats they face in the wild. All make it difficult to maintain long-term stable and healthy populations through natural seed reproduction alone. Artificial assisted propagation is therefore required to increase individual numbers and facilitate population regeneration and rejuvenation.

SCBG Researcher Wang Zhengfeng, who is also chair of the Plant Conservation Committee of the Guangdong Wildlife Conservation Association, said that the successful air-layering propagation provides a new method for the cultivation of O. purpureiflora. This will facilitate the conservation, restoration and utilisation of this rare and endangered plant, thereby establishing a virtuous cycle between conservation and utilisation. Lin Weitong, head of the Protection and Management Section of the LFS Reserve administration office, said that the LFS Reserve will build on this research achievement to further refine conservation work for rare and endangered plants, taking multiple measures to ensure their population stability and promote an increase in their numbers.

Figure 1. Pests and diseases infection during the reproductive growth stage of Ormosia purpureiflora. (A) Flower buds infested with filamentous material; (C–D) Pods/seeds damaged by feeding and infection.（Image by Wang Zhengfeng）

Figure 2. Air-layering propagation of Ormosia purpureiflora. (A–B) Preparation of the substrates for air-layering p[ropagation; (C) Carrying out air-layering propagation; (D–F) Root formation on the air-layered branches; (G–I) Cutting the rooted air-layered branches; (J) Planting the air-layered branches in seedling containers.（Image by Wang Zhengfeng）