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 contents were compared in calli grown on three culture media favouring rubber tree (Hevea brasiliensis Mull. Arg.) somatic embryogenesis to varying degrees. The percentage of embryogenic calli increased during embryogenesis induction in line with nitrate uptake, whereas ammonium uptake dropped during the same period in the following phases as this ratio tended to balance out. Free amino acids cumulated temporarily at the end of embryogenesis expression, then their content diminished. A decreasing gradient was revealed for free glutamic acid and glutamine between calli, proembryos, and developed somatic embryos. On the other hand, the protein content increased over time in the highly embryogenic culture reflecting the increasing protein content of embryos as they developed.