Changes in chlorophyll level, total N, N-soluble proteins, N-amino acids and other N compounds in a source leaf. Plants of Aviso and Oase were supplied with ample (HN, 3.75 mM) or low (LN, 0.375 mM) nitrate concentrations. These data were obtained on a selected “source leaf”, determined as mature at D0 (early bolting) and becoming senescent during the experiment. The chlorophyll amount (A; SPAD value) is expressed in an arbitrary unit. The amount of total N (B), soluble proteins (C), amino acids (D) and other N compounds (E) are expressed as mg of N per leaf for each fraction. The fraction of other N compounds that mainly corresponded to insoluble proteins, oligopeptides and ammonia, was determined as follows: mg of total N amount - (mg of N-soluble proteins + mg of N-amino acids). All these data were quantified at 0, 7 (bolting stage), 14 (flower buds raised above the youngest leaves), 21 (first petals visible, but flower buds still closed) and 28 (flowering) days after the beginning of bolting (D0). Concerning the soluble proteins and the other N compounds, only one biological replicate remained at D28, and its value is indicated by a cross (x). Data are indicated as the mean value ± standard error (vertical bars). Letters a, b and c represent differences in kinetics, asterisks indicate significant differences between treatments and hashes represent significant differences between genotypes (n = 4 plants; p < 0.05).