Phosphate availability in combination with nitrate availability affects root yield and chicon yield and quality of Belgian endive (Cichorium intybus)

This study investigated the effects of nitrate and phosphate nutrition on chicory tap root development and chicon quality. Plants of chicory (Cichorium intybus flash) were grown on four concentrations of nitrate and phosphate: 3 mM NO₃ / 1 mM PO ₄ ^3– , high N and high P (control plants, N / P); 3 mM NO ₃ ^– / 0.05 mM H₂PO^3– ₄, high N and low P (N / p); 0.6 mM NO₃ / 1 mM PO ₄ ^3– , low N and high P (n / P); 0.6 mM NO ₃ ^– / 0.05 mM PO ₄ ^3– , low N and low P (n / p). The results suggested that, nitrogen limitation had the greatest impact on the shoot/root dry weight ratio. Only small changes in the shoot/root dry weight could be attributed to P limitation alone. Compared with the control, N limitation caused a marked increase in root SST activity (sucrose sucrose fructosyl transferase, the enzyme responsible for fructan synthesis in roots), the effect of P limitation on SST activity was less pronounced. The activity of SS (sucrose synthase) was also noticeably elevated at the early sample data by N limitation. N and P uptake were estimated by the amount of N and P accumulated by the whole plant during the vegetative period. With N limitation, P accumulation was decreased by 40-60% over the experimental period. The effects of P limitation on N accumulation were more variable, N uptake was 60% lower than the control during the tuberizing period (107 days after sowing). With N limitation, P concentrations in roots were lowered by 20-25%. With P limitation, total N concentration in roots decreased by 50% relative to the control, while nitrate concentration was increased more than 8 fold. These effects were detected only at 107 DAS. The amino acid content of roots was not affected by P limitation, however, N limitation altered strongly total amino acids. P limitation did alter the relative amino acid composition of roots early in the vegetative period: Roots harvested at the end of vegetative period were forced in the dark to produce an etiolated bud, the edible chicon. High N and high P fertility (N/P) were associated to a poor chicon yield and quality. However the presence of low P during vegetative growth moderates adverse effects of high nitrate and greatly improved chicon yeild and quality.