Orchid-Fungi Symbiosis Explored in New Study

Dendrobium chrysotoxum is a species of orchid that grows on tree trunks or as epiphytes on rocks. It has great ornamental and medicinal importance. Overexploitation of D. chrysotoxum from the wild continues to pose a serious threat to the lizard’s survival.

In a previous study, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences isolated a fungal strain Tulasnella (GC-15) from D. chrysotoxum prototypes using an in situ seed trapping technique, which is significantly effective in promoting in vitro seed germination. and prototype development. However, the interaction between the protochrome D. chrysotoxum and mycobiont during seed germination remains unclear.

In a recent study published in gardeningthe researchers elucidated the prototype development process as well as the structure and characteristics of embryos and protozoa in D. chrysotoxum, in order to better understand the exchange between D. chrysotoxum and mycobiont.

Using anatomical techniques and scanning electron microscopy (SEM), the researchers studied detailed morphological changes during the symbiotic germination of D. chrysotoxum inoculated with Tulasnella sp.

There are six morphologically and anatomically identified developmental stages during symbiotic seed germination. Embryo metamorphoses into a protozoan in stage II, a bump develops from the top of the protozoan in stage III and elongates to form the cotyledon in stage IV. Stem meristem (SAM) started in stage III and was well developed in stage IV. The first leaf and root appeared at the fifth and sixth stages, respectively.

D. chrysotoxum embryos develop polarized cellular regions whose developmental outcomes are programmed. Small embryonic cells at the top develop into cotyledons and SAM, and large embryonic cells at the base develop into rhizosphere accessible by fungal hyphae and specialized parenchyma cells as a symbiotic site for fungal colonization.

“Our study provides new insights into the structure and function of orchid protozoa forms and sheds light on the symbiotic relationship between orchids and fungi,” said Lu Yan of XTBG.