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. How is the aspect of mobility of elements important to horticulture and agriculture?

Premature leaf fall is due to deficiency of

Heart rot of marigold is caused by the deficiency of

Explain the deficiency symptoms of essential elements in plants.

Deficiency of which group of elements can cause inhibition of cell division in plants?