Wang Qiu-Xia, Yan Ning, Ji Da-Gan, Li Shu-Yun, Hu Hong
Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Bot Stud. 2013 Dec;54(1):23. doi: 10.1186/1999-3110-54-23. Epub 2013 Aug 28.
Mycorrhizal associations play a key role in the life cycle and evolutionary history of orchids. All orchids grow from extremely small seeds that are lacking in reserves, and germination and growth into an underground heterotrophic, achlorophyllous stage depend upon symbiotic fungi to provide nutrient. However, the nutritional physiology between this symbiosis and green-leaved orchids is still unclear. To understand further how these associations affect growth and carbon utilization of green orchids, the green orchids were inoculated with two symbiotic fungi isolated from the roots of a wild orchid (Dendrobium officinale) in vitro and C stable isotope signature experiments were designed to analyze carbon nutrition acquisition.
After two months, both fungi had formed mycorrhizal associations with the host roots. Moreover, the growth rate was more rapid for the mycorrhizal seedlings than for the non-mycorrhizal seedlings. The mycorrhizal seedlings not only absorbed more C from the substrate, but also the S3-mycorrhizal seedlings assimilated more atmospheric CO due to significantly higher effective quantum yield of photosystem II, compared with the non-mycorrhizal seedlings. These results suggested that the green orchids could receive more C nutrition from the substrate due to symbiotic fungi, and photosynthesis capacity of the green D. officinale could be enhanced by the S3 fungus, therefore carbon nutrition acquisition also increased. As a result, the S1- and S3- mycorrhizal seedlings showed markedly higher biomass and polysaccharides contents than the non-mycorrhizal seedlings.
These results improve our understanding of the mycorrhizal functioning in the green Dendrobium and show some potential application in the cultivation of D. officinale.
菌根共生关系在兰花的生命周期和进化历史中起着关键作用。所有兰花都从极小且缺乏储备的种子生长而来，其萌发并生长进入地下异养、无叶绿素阶段依赖共生真菌提供养分。然而，这种共生关系与绿叶兰花之间的营养生理学仍不清楚。为了进一步了解这些共生关系如何影响绿色兰花的生长和碳利用，将绿色兰花在体外接种从野生兰花（铁皮石斛）根部分离的两种共生真菌，并设计了碳稳定同位素示踪实验来分析碳营养获取情况。
两个月后，两种真菌均与宿主根形成了菌根共生关系。此外，菌根化幼苗的生长速度比非菌根化幼苗更快。菌根化幼苗不仅从基质中吸收了更多的碳，而且与非菌根化幼苗相比，S3菌根化幼苗由于光系统II的有效量子产率显著更高，同化了更多的大气CO₂。这些结果表明，绿色兰花由于共生真菌能够从基质中获得更多的碳营养，并且S3真菌可以增强绿色铁皮石斛的光合作用能力，因此碳营养获取也增加。结果，S1和S3菌根化幼苗的生物量和多糖含量明显高于非菌根化幼苗。
这些结果增进了我们对绿色石斛菌根功能的理解，并显示出在铁皮石斛栽培中的一些潜在应用。
