Question

Deficiency of molybdenum causes
(a) Poor development of vasculature
(b) Bending of leaf tip
(c) Mottling and necrosis of leaves
(d) None of the above

Answer 1

Hint: Molybdenum is an essential micronutrient required for the growth of plants. Molybdenum is only required in small amounts for regular development of plants.

Complete Answer:
Molybdenum plays an important role in the regulation of various necessary plant functions.
Some plants utilize molybdenum for the conversion of inorganic phosphate to organic forms.
Molybdenum deficiencies usually resemble nitrogen deficiencies as molybdenum is closely linked to nitrogen with respect to plants. Molybdenum deficiencies are usually displayed on old and middle-aged plant leaves as molybdenum is the only mobile micronutrient.
Molybdenum deficiencies can spread up to the stem and can affect new leaves. In plants like poinsettias, a molybdenum deficiency shows up as a thin chlorotic leaf margin around the perimeter of the leaf. The leaf perimeter then becomes necrotic. A molybdenum deficiency can lead to the misshaping of leaves and can cause a whiptail effect in the midrib of the leaves of some plants like cauliflower. This puts severe restrictions on the leaf blade and the leaf becomes narrow.

Therefore, the correct answer is (c) Mottling and necrosis of leaves.

Note:
Molybdenum is an essential constituent of a couple of enzymes that convert nitrate to nitrite. This nitrite is then converted to ammonia and the ammonia is used for the synthesis of amino acids in plants. Molybdenum is also required by nitrogen fixing bacteria in legumes that fix atmospheric oxygen.