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 nitrat e and phosphate: 3 mM NO3 / 1 mM PO43-, high N and high P (control pla nts, N / P); 3 mM NO3- / 0.05 nM H2PO43-, high N and low P (N / p); 0. 6 mM NO3 / 1 mM PO43-, low N and high P (n / P); 0.6 mM NO3- / 0.05 mM PO43-, 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 t o P limitation alone. Compared with the control, N limitation caused a marked increase in root SST activity (sucrose sucrose fructosyl trans ferase, the enzyme responsible for fructan synthesis in roots), the ef fect of P limitation on SST activity was less pronounced. The activity of SS (sucrose synthase) was also noticeably elevated at the early sa mple 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 perio d. With N limitation, P accumulation was decreased by 40-60% over the experimental period. The effects of P limitation on N accumulation wer e more variable, N uptake was 60% lower than the control during the tu berizing period (107 days after sowing). With N limitation, P concentr ations in roots were lowered by 20-25%. With P limitation, total N con centration in roots decreased by 50% relative to the control, while ni trate concentration was increased more than 8 fold. These effects were detected only at 107 DAS. The amino acid content of roots was not aff ected by P limitation, however, N limitation altered strongly total am ino 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 dur ing vegetative growth moderates adverse effects of high nitrate and gr eatly improved chicon yeild and quality.