Diverse and colorful nature

Author: Gao Changling / Country: Mainland China
Publisher:
Publishing Date: 2005-07-01
Features: Tianma has been used as a medicinal plant in China for over 2,000 years, primarily to treat high blood pressure, dizziness, and hemiplegia. In recent years, it has also been used as a brain health supplement for astronauts to enhance visual nerve resolution. Due to the difficulty of cultivating Tianma artificially, it has long relied on harvesting wild Tianma for medicinal use, and its wild resources are nearly depleted. Why is artificial cultivation of Tianma so challenging? This must be understood in terms of Tianma's characteristics. Tianma is a high-level orchid plant without roots or green leaves. Its seeds are as fine as flour and lack endosperm, meaning it cannot photosynthesize to produce nutrients and has very difficult seed germination. Therefore, its reproduction, growth, and nutrition have long been mysteries in the field of biology. To decipher the mysteries of Tianma and achieve artificial cultivation, Professor Xu Jintang of the Institute of Medicinal Plants at the Chinese Academy of Medical Sciences came to the deep mountains of Qinling in Shaanxi. He finally unveiled the mystery of Tianma's companion.
Tianma resembles sweet potatoes in appearance, but cultivating it by planting tubers like sweet potatoes is ineffective. Local farmers have many tricks for digging Tianma, such as: if you see black mycelia, there might be Tianma nearby. This observation caught Professor Xu's attention. Wild Tianma often grows black root-like mycelia around tree roots or stumps. Some of these mycelia can produce mushrooms on stumps in autumn, known as "honey ring mushrooms." Professor Xu believed that honey ring mushrooms play a crucial role in Tianma's growth. Research confirmed that honey ring mushrooms invade Tianma's epidermal cells in a mycelial form, which are then digested by enzymes secreted by Tianma's digestive cells, providing nutrients to Tianma. Meanwhile, the continuous stimulation from Tianma's enzymes prompts honey ring mushrooms to absorb nutrients from tree stumps or roots and supply them to Tianma. This asexual reproduction method is rare in nature. Therefore, as long as honey ring mushrooms are collected and inoculated onto Tianma, artificial cultivation can be achieved.
Just as people were full of hope for planting Tianma, new problems arose. Honey ring mushrooms grow in places with tree roots or decaying wood, such as Quercus species like Q. myrsinifolia, Q. engleriana, and Q. stewardii. However, these trees take over a decade to regenerate after being cut, potentially causing forest damage. Using grass instead of trees for cultivation is not nutritionally sufficient. Professor Xu and his team tried using regenerative shrublands to replace tall tree forests for growing Tianma. This asexual reproduction method, when promoted in Hanzhong and other Tianma production areas in China, yielded good results and met the domestic demand for Tianma medicine.
As domestic Tianma production areas vigorously promoted cultivation techniques, new issues emerged: after multiple generations of asexual reproduction, the seed tubers severely degenerated—yielding less than what was planted. Sexual reproduction was necessary to revitalize the seed tubers and increase yields. But how could Tianma seeds germinate? Experiments showed that honey ring mushrooms, which provide nutrients during asexual reproduction, not only failed to help seed germination but also inhibited it. One night, Professor Xu suddenly recalled a farmer saying that Tianma grew from "ant eggs" under leaves. Were the farmer's "ant eggs" the round bulbils of Tianma seeds? Tests confirmed his hypothesis. By treating "ant eggs" with different methods and planting them, only seeds on leaves germinated, aligning with the farmers' claim.
Observing that some white mycelia were connected to bulbils, and finding the description "both have fine white roots, though mutually dependent, they are not actually connected" in Bencao Gangmu, Professor Xu was inspired. He cultured these white mycelia on leaves and planted seeds, screening over ten types of fungi. These fungi could only support Tianma seed germination when cultured on leaves of Quercus or Betula species. The isolated fungi had never been recorded before and could only be identified after forming fruiting bodies, i.e., mushrooms. Finally, a small mushroom, 2–3 cm tall with a 0.5 cm cap, grew on the leaves cultured by Professor Xu. Identification revealed it was Mycena purpurea.
At this point, the mysteries of Tianma's reproduction and growth were finally revealed: during seed germination (sexual reproduction), Tianma forms a symbiotic relationship with fungi in the Mycena genus. During asexual reproduction, it associates with honey ring mushrooms. Throughout its life cycle, it must rely on two types of fungi. Additionally, surveys showed that not all seeds land on suitable leaves, and not all leaves host Mycena purpurea or similar fungi. Only a small fraction of seeds germinate. However, Tianma produces millions of seeds per plant, ensuring its survival and species continuity in the long history of biological evolution.
Clarifying Tianma's life cycle laid the foundation for artificial cultivation of wild Tianma. With government support, Professor Xu's lab was established, where large quantities of honey ring mushrooms and Mycena purpurea were cultivated for artificial Tianma cultivation. In November 2002, another bountiful harvest arrived, and farmers were delighted. Relying on Tianma cultivation alone, counties like Lueyang and Mian in Shaanxi earned hundreds of millions annually. Enriched farmers spontaneously erected a statue of Professor Xu in the mountains as a tribute to the scientist.
Like other orchids, Tianma was originally a green plant. However, due to climate change, it was infected by fungi. Stronger strains survived and adapted to honey ring mushroom infection, even digesting them for nutrients. Over time, its original photosynthetic abilities gradually, retaining only the ability to digest fungi. Now, wild Tianma completely depends on symbiosis with honey ring mushrooms—it cannot survive without them.