Current Methods of Orchid Species Conservation

Being one of the largest families with close to 25, 000 representative species the Orchidaceae comprise about one tenth of all flowering plants in the world – the world’s largest plant family (Dearnaley, 2007) (Cribb, Kell, Dixon, & Barrette, 2003). Most species of orchids have horticultural value medicinal properties like Gastrodia elata, Dendrobium offcinale, Ludisia discolor (Luo, Jia, & Wang, 2003). This made it possible for the commercialization of orchids, the rise of the orchid industry and thus threatening and endangering many wild orchids as a result of over collection or habitat destruction by human activities. Accordingly, there is now the urgent need for conservation and sustainable use of orchids (Liu, Luo, & Liu, 2010). Orchids are myco-heterotropic and some are completely dependent on their fungal partners throughout their life time (Liu, Luo, & Liu, 2010). Commonly orchid seedlings have high mortality, exhibit slow growth after transplanting and is difficult to stimulate flowering.

Although, on some species this reliance on mycorrhizal fungi are reduced once they acquired their photosynthetic ability at maturity but still most species fail to grow without their fungal symbionts. Thus, in the current trend of conservation of orchid species there is the need to isolate, identify and use compatible mycorrhizal fungi (Zettler, 1997). In this paper a fungus is deemed to be an effective mycorrhizal fungus if it can: (1) promote seed germination, (2) enhance the growth of protocorms, a tuber-shaped body with rhizoids that is produced by the young seedlings of various orchids or juvenile plants, and (3) enhance the growth and reproduction of mature plants. Take the case of G. elata which is a Chinese herbal medicine that were observed to sprout only when they were able to obtain nutrition by digesting fungi like M. osmundicola which invaded its proembryo cells but once the plant has established itself it switched to the digestion of endophytes like Armillaria mellea which consequently entered its rhizome (Xu & Guo, 2000).

That this orchid had to associate with two different species of mycorrhizal fungi at different stages of its life cycle both promoting seed germination/growth and vegetative growth after establishment. To alleviate the threats to orchid species conservation approach of today involve orchid propagation for later reintroduction in the hope to establish a self-sustaining population in the natural site in the near future. This approach is reliant on the survival of orchid seedling after the transplantation from the cultivation field to the natural environment. Thus, most study focus on the plant fungi interaction that will promote and aid in seed germination and post vegetative growth. This comprehensive understanding of plant-fungi interaction would be useful in creating an alternative orchid conservation approach concerning its dwindling number.