What effect do orchid-associated fungi have on orchid growth?

Eryuan County, Yunnan Province is the main producing area of "Xiaoxuesu", and hasa long history of growingand cultivating orchids, and is a place where orchid culture has spread. It was named by the China Orchid Association as the "LianbanOrchid Garden" and is the hometown of the garden's owner, Mr. Li Yinglong. Eryuan has manyorchid growersand orchid enthusiasts. Most farming households grow Daxuesu, Xiaoxuesu, Biyusu,Lianbansu, while a small number of orchid gardens andorchid-growinghouseholds grow valuable, high-grade famous orchids such as Cangshan Qihuasu, Cangshan Qidie, Dianmei (Baocao), Lingdaihua, and Jianyangdieorchids. Orchid cultivators say: "To groworchid plantswell is not an easy thing; it is thatorchidsare difficult to grow, and this is a comment I often hear." Why is that? Becauseorchidshave special growth habits. From a biological point of view, orchids have the characteristic of nutritional "symbiosis" with fungi during their growth process. This fungus that lives symbiotically with orchids is what we call an "orchid-associated fungus" or "orchid fungus". Orchid fleshy roots are thick and fleshy, do not have root hairs, and cannot directly absorb nutrients from the soil. During growth, orchids obtain nutrients by digesting the hyphae of the orchid fungus that invade their bodies, and this nutrient supply is different from the nutrient supply of artificial fertilization. Therefore, some people call the orchid fungus theorchid'sfriend. The orchid fungus that supplies nutrients to orchids generally belongs to the genus Rhizoctonia. This type of fungus is distributed in forest areas from temperate to tropical zones, and its hyphae live widely in the soil. During the life process of the hyphae, it can secrete catalase, protease, urease, etc. to decompose cellulose, lignin, proteins, minerals, and other water-insoluble organic matter and inorganic salts, turning them into substances that can be absorbed by itself and by its symbiotic partner, the orchid. In addition, the orchid fungus can also fix free nitrogen for use by orchids and synthesize auxin, stimulating orchid root growth and sprouting. In this way, orchids continuously obtain large amounts of nutrients from the roots and pseudobulbs, and together with the effect of auxin, this promotes orchids to root, sprout, and bloom. According to the practical experience of some local skilled orchid growers, planting orchids together with orchid fungus is mutually beneficial and harmless. Orchids supply carbohydrates and metabolites to the orchid fungus, and the orchid fungus assimilates organic matter, dissolves minerals and other nutrients, and supplies them together with water for absorption by the orchid. At the same time, because the orchid fungus is stronger in life than other harmful fungi and bacteria, its massive reproduction forms a physical barrier that prevents pathogenic infection carried by orchid plants from the soil. Wild orchid plants begin to be infected by and live symbiotically with orchid fungus from the time the seeds germinate, while home-grown orchids have already directly or indirectly destroyed this symbiotic relationship during transplanting, soil changing, and seedling division. Therefore, when orchids are grown at home, seeds cannot develop into new plants, and the sprouting rate is low, making it difficult to bloom. Experiments by flower farmers with relatively strong technical skills show that after using orchid fungus planted together with orchids, in terms of seedling emergence patterns, there is no longer a distinction between autumn seedlings and spring seedlings; instead, they sprout throughout thefour seasonsof the year. Orchid plant height also shrinks year by year, leaves become wider and larger, the root system expands, and flowers are more abundant. Their growth vigor is closely related to the prosperity or decline of the symbiotic orchid fungus. Of course, to make orchids grow well, reasonable daily management methods are also very important. Such management methods also lay the foundation for creating an environment suitable for symbiosis between orchid fungus and orchids. Most orchid-growing households have reached a consensus through practice, that is, three parts transplanting and seven parts management is scientifically sound and worth learning from, promoting, and applying. (Yunnan - Zhang Shaohua)