The Effects of Changes in the Inorganic Nitrogen Supply on the Growth and Development of Marsilea in Aseptic Culture

The effects of changes in the inorganic nitrogen source of themedium on the growth and development of Marsilea in asepticculture are described. A change in nitrate concentration to0·2 or 5 x that of the normal medium had initially noeffect on growth or heteroblastic development, but in the 0·2nitrogen medium there was finally a reversion to juvenile stagesfollowed by early cessation of growth. Growth and heteroblastic development were stimulated by thesubstitution of the nitrate of the medium by ammonium saltsor urea. Nitrite was little inferior to nitrate as a nitrogensource, but hydroxylamine was toxic even at low concentrations.Addition of sodium chloride led to improved growth and developmentin nitrate media, an effect referred to beneficial effects ofthe chloride ion. Symptoms of toxicity and eventual death of the cultures whichoccurred after prolonged growth on ammonium media were due toan acid drift of the media rather than to a specific effectof the ammonium ion.