Fall of immature leaf is due to the deficiency of

Deficiency of which of the following elements checks the cell division of cambium but cell elongation continues?

Deficiency of which element causes liver necrosis and muscular dystrophy?

Deficiency symptoms of an element tend to appear first in young leaves. It indicates that the element is relatively immobile. Which one of the following elemental deficiencies would show such symptoms?

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

Why is it that in certain plants deficiency symptoms appear first in younger parts of the plant,while in others they do so in mature organs?