Altering young tomato plant growth by nitrate and CO(2) preserves the proportionate relation linking long-term organic-nitrogen accumulation to intercepted radiation
Résumé
A previously published model of crop nitrogen (N) status based on intercepted photosynthetically active radiation (R(i), mol per plant) suggested that plant organic N accumulation is related to R(i) by a constant ratio, defined hereafter as the radiation use efficiency for N (NRUE). The aim of this paper was to compare the effects of N nutrition and CO(2) enrichment on NRUE and RUE (radiation use efficiency for biomass accumulation). In three unrelated glasshouse experiments, tomato plants (Solanum lycopersicum) grown in hydroponics were fed for 28 d (exponential growth) with full solutions containing constant NO(3)(-) concentrations ([NO(3)(-)]) ranging from 0.05 to 15 mol m(-3), both under ambient or CO(2)-enriched (1000 mu l l(-1)) air. Each experiment comprised five harvests. Low [NO(3)(-)] (< 0.3 mol m(-3)) limited growth via leaf area (LA) restriction and decreased light interception. CO(2) enrichment enhanced dry weight and LA. RUE was not affected by [NO(3)(-)], but increased under CO(2)-enriched air. By contrast, NRUE was not affected by [NO(3)(-)] or CO(2) enrichment. It is suggested that the radiation efficiency for organic N acquisition (NRUE) did not depend on C or N nutrition for young plants grown under unstressed conditions.