Question

How do we decide what is essential for plants and what is not?

Answer 1

1) Out of 105 elements discovered, more than 60 elements are present in plants. However, all are not essential and this essentiality is decided by the presence of some features.

2) An essential element should have the following criterias:
i) Must be necessary for normal growth and reproduction.
ii) Specific in its action and not replaceable.
iii) Direct involvement in the metabolism.
3) They are broadly categorised into two types:
i) Macronutrients: Required in excess of 10 mmol Kg${}^{-1}$ of dry matter. These include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium, magnesium.
ii) Micronutrients: Required in less than 10 mmol Kg${}^{-1}$ of dry matter. These include iron, manganese, copper, molybdenum, zinc, boron, chlorine, nickel.