In which part will the deficiency symptoms of nitrogen and potassium first appear?

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?

Yellowish edges appear in leaves deficient in $....$

'Mottled chlorosis' on the leaves occurs due to the deficiency of

On the basis of symptoms of chlorosis in leaves,a student inferred that this was due to the deficiency of nitrogen. This inference could be correct only if we assume that yellowing of leaves appeared first in