Sources of Nitrogen for Spruce Tissue Cultures

The major heat-labile organic ingredient of the nutrient previously developed in this laboratory for spruce cells is glutamine. This cannot be fully replaced by any single stable organic substance or group of substances tested. Its replacement by inorganic ammonium salts results in no significant reduction in growth rate in terms of wet weights but produces qualitative defects which make such sutistitutions undesirable. Of special interest is the production of reticulated xylem cells when cultures are grown in the light on NH₄ supplements.