Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (3): 433-441.DOI: 10.3773/j.issn.1005-264x.2009.03.002

• Research Articles • Previous Articles     Next Articles

INTERACTION BETWEEN TISSUE-CULTURED SEEDLINGS OF DENDROBIUM OFFICINALE AND MYCORRHIZAL FUNGUS (EPULORHIZA SP.) DURING SYMBIOTIC CULTURE

JIN Hui1,2,5(), XU Zhong-Xiang3, CHEN Jin-Hua1,4, HAN Su-Fen2, GE Song1, LUO Yi-Bo1,*()   

  1. 1State Key Laboratory of Systematic and Evolutionary Botany, Chinese Academy of Sciences, Beijing 100093, China
    2College of Forest Resources and Environment, Nanjing Forestry University, Nanjing 210037, China
    3Entry-Exit Inspection and Quarantine Bureau, Nanjing, 210001
    4College of Horticulture and Landscape Architecture, Hainan University, Danzhou, Hainan 571737, China
    5Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2008-08-15 Accepted:2009-01-13 Online:2009-08-15 Published:2009-05-31
  • Contact: LUO Yi-Bo

Abstract:

Aims Dendrobium officinale is an invaluable Chinese medicinal herb in China that has been threatened by over-collection and habitat deterioration. Understanding the relationship between orchids and mycorrhizae is important for the conservation of orchids. Our aim is to examine the rela-tionship between seedling of D. officinale and mycorrhizae.

Methods The strain of GDB181 was identified by internal transcribed spacer (ITS) sequencing. We inoculated tissue culture seedlings of D. officinale with GDB181 (Epulorhiza sp.) and used ICP-AES to measure the mineral element content of the seedlings. We observed slices of the orchid mycorrhizae under light and electron microscopes.

Important findings Seedlings of D. officinale and the inoculation strain formed symbiosis effectively. The growth of seedlings was promoted by the mycorrhizal fungus. As compared with the control, in-oculated seedlings had 84.8% greater average rate of increase of fresh weight. The mineral contents were elevated except Zn; the contents of B, Si, Fe, Cu and Mn in inoculated seedlings were increased by780%, 533%, 192%, 191% and 128%, respectively. Fungal hyphae entered the exodermis by breaking the velamen randomly and infected other cells continuously by means of penetrating the cell wall. Lastly, the hyphae inhabited the large cells of the cortex and were digested. The cell wall of the cortical cells were distorted and deformed by infection by the hyphae, and many pelotons formed in exodermis and cortex. Pelotons were often found near or encircling the nucleus. The invaded fungal hyphae were surrounded and dissolved by lysosomes partly or completely. With changes of the hyphae from losing cell wall or cytoplasm to remaining cavum, the lysosomes disappeared gradually. More hyphae were dissolved and deformed if there were more lysosomes near them. The cortex cells containing degenerated hyphae were frequently recolonized by hyphae, and the hyphal digestion and the reinfection of cortex cells occurred repeatedly throughout all growing stage of D. officinale.

Key words: interaction, symbiosis, microstructure, Dendrobium officinale, Epulorhiza sp.