The development and growth requirements of Dactylorhiza purpurella in asymbiotic cultures

Abstract

Dactylorhiza purpurella was grown from seed in sterile cultures on agar slopes. The culture media consisted of combinations of minerals, dextrose or sucrose, the amino acids and vitamins etc. found in casein hydrolysate, and yeast extract. After an initial period of germination and growth, the cultures were treated with kinetin, kinetin riboside, 6(γ, γ-dimethylallylamino)purine, and indoleacetic acid (IAA), alone and in various combinations, primarily to simulate patterns of development previously obtained in symbiotic cultures.The results with dextrose and sucrose were essentially similar. Germination and growth in either case were markedly superior where casamino acids were present, and growth and survival were further improved with supplements of yeast extract to those media. On such media protocorm development was normal and in every respect as good as in symbiotic cultures. Aspartic, glutamic, and nicotinic acids appear to play vital roles in the nutrition of D. purpurella.The three aminopurines tested enhanced the shoot characters and suppressed the root characters of the protocorms, and enhanced chlorophyll formation. The results with IAA were inconclusive. The growth regulators may interact with aspartic and (or) glutamic acids with respect to morphogenesis.Iron (as ammonium ferric citrate) was deficient and limiting at 0.2 mg/liter Fe. Greener shoots, better rooting, and no harmful effects were obtained with 25 mg/liter. High levels of manganese (50 mg/liter) caused severe leaf chlorosis and hindered the beneficial effects of iron on the shoots. An Fe/Mn ratio greater than unity was necessary. Within certain limits, the right ratio may be more important than the actual levels of these cations.The effects of the growth regulators should be reassessed in relation to at least aspartic and glutamic acids, iron and manganese.