Deficiency of which mineral element causes the dormancy of lateral buds?

Death of stem and root tips occurs due to the deficiency of:

Appearance of yellowish edges in the leaves is due to deficiency of

The appearance of yellow edges to leaves is due to the deficiency of which mineral element?

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

Grey spots on oats are caused by the deficiency of which element?