Gray speck disease in oats takes place by the deficiency of

It is observed that the deficiency of a particular element shows its symptoms initially in older leaves and then in younger leaves. Does it indicate that the element is actively mobilized or relatively immobile?

Grey spots of oat are caused by the deficiency of which element?

Mottle leaf in citrus plants is due to the deficiency of:

Heart rot of marigold is caused by the deficiency of

Interveinal chlorosis of leaves is caused by the deficiency of