柑橘为亚热带常绿果树，主产区土壤多为酸性或强酸性的红壤、黄壤或砖红壤，容易遭受缺镁的危害。实际上，缺镁已成为影响我国柑橘产量和品质的重要因素之一，且呈逐年加重趋势。正因为柑橘缺镁的严重性，近年来有关柑橘缺镁的研究越来越多，但很少涉及缺镁柑橘叶脉木栓化的机理。据我们的检索，目前仅有一研究利用光学显微镜对缺镁柑橘木栓化叶脉进行了观察。有鉴于此，本项目拟在前期工作的基础上，以雪柑（Citrus sinensis）为试验材料，率先研究缺镁对柑橘叶脉解剖（光学和电子显微）结构、叶脉细胞壁多糖和木质素含量及其组分的影响，并运用RNA（Illumina/Solexa）测序和iTRAQ技术研究缺镁对柑橘叶脉转录组和蛋白质组的影响，旨在从解剖、生理生化和分子生物学水平揭示缺镁柑橘叶脉木栓化的机理，最终提高柑橘的耐缺镁能力，为实现柑橘高产优质栽培提供科学依据。

Citrus belong to evergreen subtropical fruit trees. In the major citrus production regions, citrus are cultivated mainly in acidic and strong acidic soils such as red soil, yellow soil or lateritic red soil and are usually affected by magnesium (Mg)-deficiency. Indeed, Mg-deficiency is a major factor limimting citrus yield and quality in China. Furthermore, the degree of severity is gradually increasing. Because of the severity of citrus Mg-deficiency, studies on citrus Mg-ficiency are becoming more and more. However, studies on the mechanisms for corking of Mg-deficiency citrus leaf veins are very rare. Based on our on-line retrieval, only one study compatatively observed the microscopic structure of normal leaf veins in Mg-sufficent citrus leaves and corky leaf veins in Mg-deficient citrus leaves using optical microscope. In this study, we will use ‘Xuegan’ (Citrus sinensis) as the materials and take the lead in investigating the effects of Mg-deficiency on leaf veins using optical and electron microscopes and the contents of cell wall polysaccharides and ligin and their composition in leaf veins. In addition, we will investigate the effects of Mg-deficiency on transcriptome and proteome in citrus leaf veins using RNA （Illumina/Solexa）sequencing and iTRAQ technique for the first time. The objectives of this study are to elucidate the mechanisms on corking of Mg-deficiency citrus leaf veins at microscopic structural, physiological and biochemical, and molecular biological levels, finially enhancing the tolerance of citrus plants to Mg-deficiency, and provide scientific basis for citrus cultivation of high yield and good quality.