The criteria for essentiality of an element for a plant include all except:
1. It must be absolutely necessary for supporting normal growth and reproduction
2. The requirement must be specific and not replaceable by another element
3. It must be directly involved in the metabolism of the plant.
4. They must be present in the plants in a concentration in excess of 10 mmole/Kg of dry matter.
(4) Read Page 195/196, XI NCERT