Search

• N-deficient citrus leaves and roots kept high abilities to detoxify ROS and MG. • N-deficiency (ND) affected ROS and MG metabolism more in roots than in leaves. • ND enhanced n distribution in roots and R/S, and delayed root senescence. • ND reduced MDA levels and electrolyte leakage in citrus leaves and roots. Nitrogen-deficiency (ND) usually occurs in some citrus orchard soils in China. The roles of reactive oxygen species (ROS) and methylglyoxal (MG) generation and their detoxification systems in ND tolerance of horticultural woody plants still need to be revealed. For the first time, we examined the effects of ND on ROS and MG generation and their detoxification systems in leaves and roots of Citrus sinensis seedlings. The objectives are to test the hypotheses that N-deficient leaves and roots can keep high abilities to scavenge ROS and MG, thereby protecting them from oxidative damage, and that ND-induced alterations of ROS and MG formation and their detoxification systems in leaves and roots are different. ND augmented superoxide anion production rate and MG concentrations, but it decreased malondialdehyde (MDA) concentrations and electrolyte leakage in leaves and roots. ND increased the activities of most enzymes involved in ROS (ascorbate-glutathione cycle-related enzymes, antioxidant enzymes, and sulfur metabolism-related enzymes) and MG (glyoxalases) detoxification expressed on a protein basis with a few exceptions, and the concentrations of ascorbate, phytochelatins, and total non-protein thiols in leaves and roots. These results suggested that nitrogen-deficient leaves and roots could keep high abilities to detoxify ROS and MG, and protect them from oxidative damage. Generally viewed, ND affected the production and removal of ROS and MG more in roots than in leaves. [ABSTRACT FROM AUTHOR]

• Magnesium deficiency induces leaf chlorosis, leaf curling and impaired growth of C.sinensis seedlings. • Magnesium deficiency upregulates the relative abundances of most monosaccharides and amino acids in C.sinensis leaves. • Magnesium deficiency decreases the relative abundances of most pigment compounds and organic acids in C.sinensis leaves. In south China, Magnesium (Mg) deficiency is commonly found in Citrus orchard due to soil acidification. However, less information is available discussing the global metabolic profile of Mg-deficient leaves in Citrus species. In the study, seedlings of 'Xuegan' [ Citrus sinensis (L.) Osbeck] were treated with Mg-plus (2 mM, as Control) or Mg-deficiency (0 mM) for 16 weeks by sandy culture, respectively. The untargeted metabolomics based on UHPLC-Q-TOF/MS were investigated to reveal the metabolic responses to Mg-deficiency in leaves of C. sinensis. The results indicated severe growth inhibition and obvious leaf chlorosis in Mg-deficient seedlings of C. sinensis compared to control. The principal component analysis (PCA) and orthogonal partial least squares-discriminate analysis (OPLS-DA) on the LC/GC data demonstrated a clear discrimination between the profiles of metabolites in control leaves and Mg-deficient leaves of C.sinensis. Besides, the identification and classification of those differential expressed metabolites (DEMs) revealed Mg-deficiency upregulated relative abundances of 78.42 % lipids and lipid-like molecules. In contrast, Mg-deficiency downregulated 89.42 % phenylpropanoids and polyketides in leaves of C.sinensis. Remarkably, relative abundances of most monosaccharides and amino acids increased while relative abundances of most leaf pigment compounds and organic acids decreased in response to Mg-deficiency in C. sinensis leaves. Those results support both primary and secondary metabolic modifications in C. sinensis leaves exposed to Mg-deficiency. Overall, the findings of present study contribute to a better understanding on the metabolic changes of Mg-deficient Citrus species, which will provide references for nutrient management and quality control in Citrus production. [ABSTRACT FROM AUTHOR]