EFFECTS OF EXOGENOUS AMINO ACIDS ON THE DEVELOPMENT OF MARCHANTIA POLYMORPHA GEMMALINGS

The effects of various nitrogenous compounds in concentrations ranging from 10 ‐4 to 10 ‐3 m on the growth and morphology of gemmae of Marchantia polymorpha L. were investigated under axenic conditions. Only nine of the 24 compounds tested were effective in altering the normal developmental pattern of this plant. l ‐Isoleucine, l ‐leucine, l ‐methionine or l ‐threonine resulted in a disruption of the apical regions at concentrations of 10 ‐3 m . The addition of lower concentrations of l ‐arginine, l ‐histidine, l ‐hydroxyproline, l ‐lysine or l ‐tryptophan to the nutrient medium resulted in morphological irregularities. These latter abnormal growth patterns were highly specific for the individual amino acids and ranged from lack of air chamber development to complete thallus disorganization. Both the formation and duration of abnormal developmental patterns were dependent upon the concentration of the amino acids employed. Although the experimental results are inconsistent with certain physiological mechanisms such as a general nitrogen toxicity, alternative possibilities are discussed.