| (d)The criteria for essentially of an
element are given below(i) The element must be absolutely
necessary for supporting normal growth and reproduction. In the absence of
the element, the plants do not complete their life cycle or set the seeds(ii) The requirement of the element
must be specific and not replaceable by any another element. In other words,
deficiency of any one element cannot be met by supplying some other element(iii) The element must be directly
involved in the metabolism of the plant |