INFLUENCE OF MINERAL NITROGEN FORMS UPON ATP FORMATION IN THE LEAVES OF C-3 AND C-4 PLANTS

Maize (Zea mays L.), amaranth (Amaranthus paniculatus L.) and wheat (T riticum aestivum L.) were grown under natural irradiance in hydroponic s on full nutrient solutions with nitrates or ammonium as a sole sourc e of nitrogen [153.2 g(N) m(-3)]. The photophosphorylating (PP) activi ty of the chloroplasts isolated from mature wheat leaves was higher in the ammonium variant than in the nitrate one. Opposite tendency was c haracteristic for chloroplasts of mesophyll and bundle sheath cells is olated from maize leaves. The PP activity in leaf discs (measured as i ncorporation of P-33(i) into ATP) in the ammonium variant was 64 and 3 1 % of that in the nitrate variant for maize and amaranth, respectivel y. In wheat leaf discs the difference between the two variants was ins ignificant. During the period of maximal photosynthesis, the ATP conte nt in leaves of plants grown with nitrates was nearly 10 and 80 % high er than in the ammonium variant for maize and amaranth, respectively. In wheat leaves the ammonium nutrition enhanced the ATP content by 10 % in comparison with the nitrate one. The content of free ammonium ion s was always higher in the leaves of plants grown with ammonium nutrie nt solution. The ammonium ions probably uncouple PP in the plants grow n with ammonium as a sole source of nitrogen.