In vitro orchids (Blog 1)

Orchid seeds:

The seeds of orchids are very minute with a very small embryo and lack on endosperm (Arditti (1992), found in Sathiyadash et al. (2013)). The difference from orchid seeds to other plant seeds is the lack of storage tissues required for seed germination and seedling development (Paudel et al. (2012)). Orchids are mycoheterotrophic during their seedling stage. That means that they are dependent on fungi as a carbohydrate source (Rasmussen (2002)). In nature the seeds of orchids cannot be induced to germinate and grow in the absence of a mycorrhizal fungus (Smith (2008)).

In vitro orchids:

Bio-conservation and in vitro sowing of orchids is an important aspect in the orchid multiplication and conservation. When sugars and various growth factors are supplied it is possible that the dust like tiny orchid seeds develop into complete seedlings without any fungal aid. This does not occur in nature but in vitro it is possible (Paudel et al. (2012)).

Appropriate mycorrhiza strain:

To find an appropriate mycorrhiza strain for In vitro sowing take a mycorrhiza from an orchid in nature. They have to be isolated from the roots of the orchid and they can be identified using the nuclear ribosomal internal transcribed spacer (ITS) and 5.8S rDNA sequences (Ming Tan et al. (2013)). Tan X. M. et al. isolated two Tulasnella strains from roots of endangered species and evaluated seed germination and plant growth of Dendrobium officinale after interaction with the mycorrhiza. They found out that the two different strains of the mycorrhizal fungi Tulasnella sp. have different impact on germination and development of Dendrobium officinale.

Literature:

Kullaiyan Sathiyadash, Thangavelu Muthukumar , Shanmugaraj Bala Murugan , Ramalingam Sathishkumar , Radha Raman Pandey. 2013. In vitro symbiotic seed germination of South Indian endemic orchid Coelogyne nervosa. Mycoscinece 55 (2014).

M.Paudel, S.Pradhan, B.Pant. 2012. In vitro Seed Germination and Seedling Development of Esmeralda clarkei RCH.f. Plant Tissue Cult. & Biotech.

Hanne N.Rasmussen. 2001. Recent developments in the study of orchid mycorrhiza. Plant and soil.

Sally E. Smith, David Read. 2008. 12-The mycorrhizas of green orchids. Mycorrhizal Symbiosis.

Xiao Ming Tan, Chun Lan Wang, Xiao Mei Chen,  Ya Qin Zhou, Yun Qiang Wang, An Xiong Luo, Zhi Hua Liu, Shun Xing Guo. 2013. In vitro seed germination and seedling growth of an endangered epiphytic orchid, Dendrobium officinale, endemic to China using mycorrhizal fungi (Tulasnella sp.). Scienta Horticulturae (2014).