It is found in seawater and all plants and animals. Magnesium is an essential element in chlorophyll, and acts as a carrier for phosphorus. Magnesium is the central atom in chlorophyll supplying the green pigment. Magnesium is highly mobile, so first signs of deficiency are in older leaves.
Lower leaves become lighter in color and turn brittle.
The leaf loses color between veins, then progresses to brown dead areas. The mottling of tissue that loses green color is a common sign. Leaf edges lose color and the interiors near the veins stay green. It can show up as yellow stripes on leaves such as grasses and corn. It is relatively abundant in seeds and leaves.