Altering young tomato plant growth by nitrate and CO2 preserves the proportionate relation linking long-term organic-nitrogen accumulation to intercepted radiation

Abstract

• A previously published model of crop nitrogen (N) status based on intercepted photosynthetically active radiation (Ri, mol per plant) suggested that plant organic N accumulation is related to Ri 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 NO3- concentrations ([NO3-]) ranging from 0.05 to 15 mol m -3, both under ambient or CO2-enriched (1000 μl 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. CO2 enrichment enhanced dry weight and LA. RUE was not affected by [NO 3-], but increased under CO2-enriched air. By contrast, NRUE was not affected by [NO3-] 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. © The Authors (2008).