An element required for pollen germination is

A. Molybdenum

B. Potassium

C. Boron

D. Iron

A. Molybdenum is absorbed by the plants in the form of molybdate ions. It is also absorbed in the forms of di, tri or pentoxides. It is required all over the plant particularly by roots in the form of molybdate ions. The most important function of this is in nitrate reduction, and nitrogen fixation.

B. Potassium is obtained by the plants in the form of potassium sulfate, potassium nitrate, etc. Potassium is usually present in the sufficient amount in the clay soils where it is firmly bound. It is required in meristematic and differentiating tissues. Potassium accumulates in older leaves. It appears to have no structural roles in plants but it serves a number of catalytic roles. The deficiency in potassium affects physiological processes like respiration, photosynthesis and chlorophyll development.

C. Boron appears in exchangeable soluble and non-exchangeable forms in the soil. It is present in the form of boric acid, calcium and magnesium borates and is a constituent of silicates. Its calcium and magnesium salts are soluble. Plants require boron in leaves and seeds. It is required for uptake and utilization of calcium, pollen germination and cell differentiation and carbohydrate translocation. It also plays an important role in nitrogen metabolism, hormone metabolism and fat metabolism. It regulates cellular differentiation and development.

D. Iron is made available to the plant in the form of ferric ions. It is required everywhere in the plant and collects along the leaf veins. It is a constituent of ferredoxin and cytochromes. Iron activates catalase. It plays an important role in the formation of chlorophyll. It takes part in the photosynthesis and in respiration for the release of energy. Iron is a component of flavoproteins.