Plants use minerals from the soil and energy from the sun to produce food.
Plants need certain elements to produce important compounds. They get these mineral ions from the soil. If there are not enough of these ions, plants suffer deficiency symptoms.

Phosphates.
Contain phosphorus for making DNA and cell membranes. These are needed for respiration and growth. Plants deficient will have poor root growth and purple older leaves.

Magnesium.
Needed in smaller amounts. Magnesium is used for the production of chlorophyll. plants deficient will have yellow leaves.