Abstract: Boron（B）and magnesium（Mg）are essential mineral nutrients for plant growth and survival. Here by inductively coupled plasma-atomic emission spectrometry（ICP），11 nutrient elements in citrus matured spring leaves[including Fortunella crassifolia Swingle，Citrus senisis（L.） and C. Grandis（L.）]，of which vein splitted，were determined，and their anatomic structure were also analysed by paraffin section. Results were as follow：B and Mg deficiency both could lead to cracking of vein surface，dysplasia of vascular tissue and separation of sclerenchyma in citrus leaves. The boundary between xylem and phloem in vascular bundle was clear，and ray structure remained intact in leave that suffered from B deficiency. Besides，B deficiency caused necrosis of primary phloem and cortex in midrib，necrosis of primary phloem in lateral veins，as well as hyperplasia of spongy tissue. However，dispersion of epigenetic xylem structure and wooden-ray structure was detected in leaves that suffered from Mg deficiency. Mg deficiency caused a reduction in number and structural changes of chloroplast，necrosis of pith and primary phloem in midrib，tylosis in vessel elements of primary xylem in lateral veins，as well as hyperplasia of primary phloem. Tylosis in vessel elements and irregular hyperplasia of xylem，and necrosis of pith in midrib could be used as diagnostic criteria for Mg deficiency in citrus plants.

Key words: citrus, boron deficiency, magnesium deficiency, leaf, vessel tissue, parenchyma cell, chloroplast