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Summary

The effect of some growth substances on gernnination and development of Orchis (Dactylorchis) purpurella seeds was studied in an attempt to simulate the developmental pattern observed in symbiotic cultures.

Gibberellic acid enhanced protocorm survival and caused abnormal elongation of the emergent shoot but did not influence the growth and overall size of the protocorms. Indoleacetic acid impeded germination and caused some elongation of the protocorms. Kinetin, both alone and in conjunction with indoleacetic acid, had a pronounced effect on growth and development and the results suggested that the auxin/cytokinin ratio is important in controlling root and shoot initiation. Adenine appeared to have little effect.

The growth factor mixtures used did not have as beneficial an effect on protocorm development as did the presence of either symbiotic fungi or undefined fractions such as potato extract and coconut milk, suggesting that symbiotic fungi also provide other growth substances.