Define the following terms:
$(1)$ Chlorosis
$(2)$ Necrosis

(N/A) $(1)$ Chlorosis: It is the loss of chlorophyll in leaves,which leads to the yellowing of leaf tissue. It is caused by the deficiency of elements like $N, K, Mg, S, Fe, Mn, Zn$ and $Mo$.
$(2)$ Necrosis: It is the localized death of plant tissues,particularly leaf tissue. It is caused by the deficiency of $Ca, Mg, Cu$ and $K$.