Seed Sowing.

Copyrights © Reserved Markus Axelsson, 2005.

Sowing

Seeds contain embryonic cells that are totipotent. Orchid seeds don't have the nutrients (endosperm) needed to develop. The germination must be taken care of with energy from some other organism. Naturally, this happens through mykorrhiza, but can also be imitated artificially in a laboratory. All nutrients that are needed for the seed to germinate and for the little embryo inside to wake up and start dividing, has to be formulated into a medium. This nutrient substrate is the only thing that nourishes the cells.

There are two methods that are applied when growing orchids from seeds. ( In some cases, seeds must be pre-treated with e.g. gibberellins to germinate.);

Symbiotic. The seeds are spread out on a medium with nutrients and a fungus (a special fungi known to be able to infect the seeds and nourish them.
Asymbiotic. A medium with sugar [2%] and nutrients is used. The seeds are spread out and let to germinate from the nutrients and sugar available through the nutrient substrate.

Then what?

The small (often green) cell-tubers are called protocorms and can only be derived from seeds. (protocorms can not be produced via embryogenesis from explants and callus). The germination can take up to several months.

Protocorm is let to grow and are then moved to a fresh medium with higher concentrations of nutrients. Seedlings can start to develop. One can also star a callus-proliferation from protocorm (with the use of hormones).

(Do not mix protocorm with protocorm-like bodies. The latter are only protocorm-like (just as the name suggests). These tuber-like structures are also cell-aggregates but have been derived from explants and are thus clones.)

Sowing of terrestrial species - somewhat worse

It can be tricky growing terrestrial orchids. Both symbiotic and asymbiotic cultures have succeeded, but there have been difficulties in isolating the right strands of fungi to do the symbiotic job (Kew). There are theories about a decreasing need of symbiotic partners as the orchid gets older. Some species however, have leafless periods or are chlorophyll-less, meaning that they are completely depended on their fungiae. They do parasite on the fungi.

Before sowing, some seeds need a stratification (cold-room, 4°C, during three months) to even germinate at all (Kew). A pre-procedure, to have certain seeds germinate easier, is done by using concentrated calcium hypochlorite or concentrated sodium hypochlorite for several hours (looking for a change in colour) (Aaron Hicks, Orchid Seedbank Project, 1999).

The European species are somewhat sensitive towards light (Ramsay, 1998). They are let to germinate in the dark (seeds from tropical epiphytes are generally germinated under periods of illumination).

Svante Malmgren is a Swedish medical doctor with an interest in orchids. It's been told that he's been fairly successful with terrestrials in culture. He has also formulated a few media of his own. (Malmgren has been using Soluvit and Vamin, peptide-solutions). Hydrolysed casein [200-400mg/L] and peptides from health stores can be used in a similar fashion (Orchid seedbank project; 2000).

Terrestrial orchids from temperate habitats demand a certain period of cold temperatures (e.g. three months in 4°C during winter).

... Deflasking