The Orchidaceae family is among the largest and most diverse groups of flowering plants with 10% of all systematically verified angiosperms and 40% of monocotyledon species. The fascinating flower morphology, tiny and particular seed, specialized pollination systems and reproduction cycle, as well as the complicated symbiotic relationship with mycorrhizal fungi, have made orchids the species of interest for many comprehensive scientific studies. Wild orchids have been declining as a result of the beauty and mysticism they are known for. In recent years, the high demand for hot Salep drinks and Salep-based ice creams and other food and medicinal products has attracted the attention of collectors to supply tuber material from wild terrestrial and tuberous orchids. Therefore, terrestrial orchids are at the front line of extinction, with a higher number of endangered species compared to other orchid types. Terrestrial orchids have a long-life cycle (2-5 years) to enter the reproductive phase. Seeds, protocorms, juveniles, dormant adults, vegetative adults and flowering individuals account for the six primary stages of the terrestrial orchid life cycle. All orchids including terrestrial species have tiny and dust-like seeds, which makes the tracing of seed dispersal and monitoring of germination and plantlet growth, rather challenging. Orchids are highly dependent on fungi called mycorrhizae to provide carbon and nutrients for symbiotic germination. This dependence on mycorrhizal fungi is because orchids produce thousands of tiny seeds per capsule, and these seeds generally have either limited or no energy resources for germination and initial growth in their tiny endosperms. The lignified, pectin layers of seed testa can act as a barrier for water uptake, embryo enlargement and, in laboratory conditions, prevent seed germination in terrestrial orchids. One of the strategies to soften and eliminate the strong and impenetrable testa is the treatment with sodium hypocrite (NaOCl) which simultaneously disinfects and scarifies seeds. Terrestrial orchids are growing in natural habitats with low strength of available nutrients and therefore the reported nitrate sensitivity in asymbiotic seed germination of terrestrial orchids may be part of their adaptive strategy. However, almost all terrestrial orchid species need a symbiosis relationship with mycorrhizal fungi to germinate their seeds, develop the protocorms and establish plantlets in nature. In cultivation, these events can also be proceeded both symbiotically (in the presence of fungal symbiont) or asymbiotically (without fungal symbiont). Asymbiotic germination procedures possess advantages including an easier cultivation process, fast and large-scale in vitro plantlet production and direct investigation of important variables affecting different biological aspects of orchids’ life. Depending on the genus, species and even sub-species, there are different developmental requirements, in particular, based on the climate origin (tropical and temperate), which necessitate the investigation of technically different germination procedures.
