Description of the development stages from the orchid cultures



Picture 1: Development stages of orchids

 

Since the transfer of the orchid seeds to the petri dish at week 9 (28.02.2013), the seedlings haven’t changed in size and shape very much. They look almost the same as in the beginning. See picture number two.

Picture 2: the embryo in the testa (09.04.2013)

In the petri dishes with the mycorrhiza, it seems that the growth rate of the fungus and the seeds aren´t in balance. The fungus grew much faster and eliminated the seeds.
Usually the seeds start to swell after a time and the embryo then fills out the testa. See picture number tree.


Picture 3: the swollen embryo in the testa (14.03.2013)

During this time, the seeds are protected from mechanical damages by the testa. Later the testa ruptures. This process can be triggered through the increase of the seed, the mycorrhizal excretion or the ingrowth of the hyphae in the testa (www.dgfm-ev.de/sites/default/files/ZM512185Beyrle.pdf). Then a protocorm with rhizoids evolve. In the asymbiotic variant (without mycorrhiza), the rhizoids absorbs the nutrients directly from the medium. In the symbiotic variant, the seeds germination is the same as in nature. The development of the protocorm is supported by the mycorrhizal fungus, which provides the necessary nutrients.

Picture 4: Protocorm wirh rhizoids (09.04.2013)

Due to the nutrients, the protocorm will be able to grow further. After a certain period of time the roots and cotyledons will develop.

In our experiment the seeds aren’t develop in the asybiotic and the symbiotic variant. One reason could be that the capsules we used were harvested too early and therefore they aren’t  germinated.