镁是叶绿素的成分，缺镁叶片褪绿，作物难以合成碳水化合物；镁是很多酶的活化剂，如果糖激酶，半乳糖激酶等许多参与碳水化合物代谢的酶都要镁离子作活化剂，一些参与氮和磷素代谢的酶也要镁离子来活化，镁还有促进脂肪合成的作用。

Magnesium is a component of chlorophyll, and it is difficult for crops to synthesize carbohydrates due to Magnesium deficiency. Magnesium is the activator of many enzymes, such as Sugar kinase and galactokinase and many enzymes involved in carbohydrate metabolism need magnesium ions as activator. Some enzymes involved in nitrogen and phosphorus metabolism also need magnesium ions to activate. Magnesium can also promote fat synthesis.

镁在植物体中易从老器官转移到新生器官中，所以，缺镁首先在植株下部老叶表现症状。缺镁时，叶片叶脉间褪绿，以后变为均匀的淡黄色或白色，叶内部分组织变褐甚至坏死，某些作物如柑桔叶片基部呈倒∧形保持绿色，而许多蔬菜是叶边缘发黄。

Magnesium is easy to transfer from old organs to new organs in plants. Therefore, the symptoms of magnesium deficiency first appear in the lower old leaves of plants. In the absence of magnesium, the leaf vein chlorosis, then become uniform pale yellow or white, some of the tissue inside the leaf become brown or even necrosis, some crops such as citrus leaf base is inverted Λ shape, keep green, while many vegetables are yellow leaf edge.

植物缺镁的原因可能是土壤酸性强，或土壤含钙量高，或是施钾肥太多，而诱发缺镁，缺镁作物喷1%硝酸镁溶液或者0.08%螯合镁，可获良好效果。

Magnesium deficiency may be caused by strong acidity of soil, high calcium content of soil, or excessive application of potassium fertilizer. Spraying 1% magnesium nitrate solution or 0.08% chelated magnesium on magnesium deficient crops can obtain good results.