1. When mineral element is present below a certain critical concentration it is said to be deficient.
2. Symptoms are indicated in the form of certain morphological changes on the mobility of element.
3. These symptoms depend on the mobility of element inside the plant body.
4. When the element is relatively immobile like S, Ca then the symptoms appear first in young leaves.
5. When the elements are actively mobilised inside plant body, they are transported to young tissues then the symptoms are visible in older, i.e. senescent leaves e.g. N, Mg, K
