Nitrate Accumulation and Reduction in Lettuce as Influenced by Nitrogen Fertilization Rate and Genotype

in HortScience

The objective of this study was to investigate the effect of solution \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}concentration (Ns), in a recirculating hydroponic system, on the accumulation and partitioning of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}and reduced N, and its relationship to root and leaf nitrate reductase activity (NRA), in five lettuce (Lactuca sativa L.) cultivars differing in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation capacity. Significant interactions between Ns and genotype influenced \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation, reduced N levels, and NRA in roots and leaves. In two cultivars, leaf \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}concentrations increased with increasing Ns up to 5.0 mM, and then leveled off, while in three other cultivars, leaf \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}levels increased linearly with increasing Ns rate up to 15.0 mM. NRA in leaves was generally highest at 5.0 mM Ns, and tended to decrease at 15.0 mM Ns. In roots, NRA increased with increasing Ns rate up to 1.0 mM, and remained relatively constant as Ns increased to 5.0 and 15.0 mM. In each cultivar, in situ \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}reduction (estimated by the relative concentrations of tissue reduced N to total N) decreased in both roots and shoots as Ns increased. The results suggested that genotypic variation in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation in response to increasing Ns was not exclusively a result of cultivar differences in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}uptake and reduction capacity, but may also involve other factors in relation to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation.

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