RELATION BETWEEN NITROGEN UPTAKE, AMINO-ACID CONTENTS, AND EMBRYOGENIC INTENSITY OF RUBBER TREE CALLI

Ammonium and nitrate uptake as well as free and protein amino acid con tents were compared in calli grown on three culture media favouring ru bber tree (Hevea brasiliensis Mull. Arg.) somatic embryogenesis to var ying degrees. The percentage of embryogenic calli increased during emb ryogenesis induction in line with nitrate uptake, whereas ammonium upt ake dropped during the same period in the following phases as this rat io tended to balance out. Free amino acids cumulated temporarily at th e end of embryogenesis expression, then their content diminished. A de creasing gradient was revealed for free glutamic acid and glutamine be tween calli, proembryos, and developed somatic embryos. On the other h and, the protein content increased over time in the highly embryogenic culture reflecting the increasing protein content of embryos as they developed.