Question

Mention the criteria for essentially of an element. Give one example of an essential element.

Answer 1

Amon and Stout proposed criteria for knowing the essentiality of an element. They are :

(a) It is indispensable for the growth of the plant.

(b) The element is directly involved in the nutrition of plants. It becomes a component of either a structural or functional molecule. The element may additionally have a corrective effect on mineral balance and other soil conditions.

(c) A plant is unable to complete its vegetative or reproductive phase in the absence of the element.

(d) The element cannot be replaced by any other element.

(e) The absence or deficiency of the element produces disorders that are a direct result of the lack or deficiency of the element.

(f) The element alone can correct the disorders produced by its absence or deficiency.

16 elements have been found to be essential. They are $C,H,O,N,P,K,S,Mg,Ca,Fe,B,Mn,Cu,Zn,Mo,Cl$. Nickel has been made the seventeenth essential element.