In 2 experiments spring wheat cv. Solo was grown in hydroculture under greenhouse conditions. The influence of cytokinin applications during grain filling period (Cy: 0-100 .mu.g BA/l nutrient solution) combined with different N supply (N:0, 0.25, 0.50 and 4.0/1.3 mM/l) was studied in regard to the development of flag leaves and grains. As to flag leaf, only N was capable to increase specific fresh and dry matter and delay the decrease during development. Similar changes in the chlorophyll content, photosynthesis and N-content of leaves and grains, respectively, could be induced by either N or Cy. Grain growth and grain N-content was favored by N, with the 1st effect becoming visible early and the second late in the grain filling period. At maturity Cy gave the same effects, but time course was slightly modified. At high doses of N (4.0/1.3 mM/l) Cy-applications reduced chlorophyll content, photosynthesis and N-content of leaves and grains. This gave rise to the conclusion that cytokinins limit the corresponding physiological processes only if N nutrition is low.