Relatively uniform loss of color in leaves, occurring first on the older ones, is usually a sign of deficiency of which of the following?

A. potassium

B. iron

C. nitrogen

D. magnesium

E. boron

Answer: D. magnesium

Explanation:

Chlorosis is a condition in which the leaves of the green plants do not have enough nutrients so as to synthesize the chlorophyll to keep the leaves green. Thus the leaves loose their color. The loss of chlorophyll from the older leaves is the characteristic feature of magnesium deficiency. It happens when the soil in which the plants are growing lacks magnesium.