It is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves.
(a) Does it indicate that the element is actively mobilised or relatively immobile ?
(b) Name two elements which are highly mobile and two which are relatively immobile.
(c) How is the aspect of mobility of elements important to horticulture and angriculture ?

Explanation

(a) It represents the active mobility of element. The deficiency tend to appear first in older leaves.
(b) Highly mobile elements: Potassium and zinc Immobile elements: Calcium and sulphur.
(c) The appearance of deficiency symptoms exhibits the mobility or immobility of element. It is seen that whether it first appears in older leaves or younger leaves. By proving the deficient element, growth of plants can be increased in horticulture and agriculture.