Nitrate ( 15 NO 3 ) limitation affects nitrogen partitioning between metabolic and storage sinks and nitrogen reserve accumulation in chicory ( Cichorium intybus L.)

Abstract

In chicory, we examined how NO 3 A supply aected NO 3 A uptake, N partitioning between shoot and root and N accumulation in the tuberized root throughout the vegetative period. Plants were grown at two NO 3 A concentrations: 0.6 and 3 mM. We used 15 N-labelling/ chase experiments for the quanti®cation of N¯uxes between shoot and root and for determining whether N stored in the tuberized root originates from N remobilized from the shoot or from recently absorbed NO 3A . The rate of 15 NO 3 A uptake was decreased by low NO 3 A availability at all stages of growth. In young plants (10±55 days after sowing; DAS), in both NO 3 A treatments the leaves were the strongest sink for 15 N. In mature (tuberizing) plants, (55±115 DAS), the rate of 15 NO 3 A uptake increased as well as the amount of exogenous N allocated to the root. In N-limited plants, N allocation to the tuberized root relied essentially on recent N absorption, while in N-replete plants, N remobilized from the shoot contributed more to N-reserve accumulation in the root. In senescing plants (115±170 DAS) the rate of 15 NO 3 A uptake decreased mainly in N-replete plants whereas it remained almost unchanged in N-limited plants. In both NO 3 A treatments the tuberized root was the strongest sink for recently absorbed N. Remobilization of previously absorbed N from shoot to tuberized root increased greatly in N-limited plants, whereas it increased slightly in N-replete plants. As a consequence, accumulation of the N-storage compounds vegetative storage protein (VSP) and arginine was delayed until later in the vegetative period in N-limited plants. Our results show that although the dynamics of N storage was aected by NO 3 A supply, the ®nal content of total N, VSP and arginine in roots was almost the same in N-limited and N-replete plants. This indicates that chicory is able to build up a store of available N-reserves, even when plants are grown on low N. We also suggest that in tuberized roots there is a maximal capacity for N accumulation, which was reached earlier (soon after 100 DAS) in N-replete plants. This hypothesis is supported by the fact that in N-replete plants despite NO 3 A availability, N accumulation ceased and signi®cant amounts of N were lost due to N eux.Abbreviations: DAS = days after sowing; 2-D = two-dimensional; VSP = vegetative storage protein Correspondence to: A.M. Limami; Fax: 33 (1) 30 83 30 96

Fructan production in Vernonia herbacea (Vell.) Rusby is related to adequate nitrogen supply and period of cultivation

“…The high values of fructan contents observed in N-limited plants (figure 4) are consistent with other studies that showed an inverse relationship between fructan content and nitrogen concentration (Améziane et al 1997, Wang & Tilberg 1996, McGrath et al 1997, Van den Ende et al 1999. However, the fructan yield after 180 days was lower in plants transferred to N-limited solution due to their lower rhizophore biomass (figure 3), as previously reported for plants of V. herbacea cultivated exclusively under N-sufficient or N-limited conditions during one year (Cuzzuol et al 2005b).…”

“…The reduction of cell division and cell expansion, leaf production and photosynthesis are evident effects in response to nitrogen deficiency . In some species of Asteraceae and Poaceae, for example, nitrogen restriction increased the contents of fructan-type carbohydrates (Wang & Tilberg 1996, Améziane et al 1997, Van den Ende et al 1999.…”

Genetic variability of nitrogen accumulation during vegetative development and remobilization during the forcing process in witloof chicory tuberized root (Cichorium intybus L.)

“…Negligible differences between the genotypes for total protein accumulation and remobilization were observed despite important differences in total N and total amino acid accumulation. These results are in agreement with those of Améziane et al (1997) and RichardMolard et al (1999), who showed, in C. intybus L. cv. Bea, that neither protein accumulation in tuberized roots at the end of the vegetative phase nor protein mobilization during the forcing process or flowering in natural conditions were significantly affected by nitrogen fertilization levels.…”

Elevated CO2concentrations increase leaf nitrate reduction by strengthening sink activity in soybean plants

“…These results confirmed that the efflux of nitrogenous compounds from the leaf was controlled by the sink activity of the pods. This is similar to the situation in chicory, where the storage organ (tuberised root) was found to be the strongest sink for newly absorbed N (Ameziane et al 1997).…”