The die-back disease in Citrus is due to deficiency of . . . . . . .

In a $Citrus$ plantation,all the plants were found to be suffering from the die-back disease,and spraying of fungicides was of no help. This problem was due to the deficiency of:

Match the following columns:

Column-$I$	Column-$II$
$P$. Chlorosis	$I$. $Ca, Mg, Cu, K$
$Q$. Necrosis	$II$. $N, S, Mo$
$R$. Inhibition of cell division	$III$. $N, K, Mg, S, Fe, Mn, Zn, Mo$
$S$. Delay in flowering	$IV$. $N, K, S, Mo$

Interveinal chlorosis of leaves is caused by the deficiency of

In plants,a common symptom caused by the deficiency of $P, K, Ca$ and $Mg$ is the

Deficiency symptoms of mineral elements appear first in young leaves. - $P$
Deficiency symptoms of mineral elements appear first in senescent (older) leaves. - $Q$
$P$ and $Q$ are respectively: