An element playing important role in nitrogen fixation is
(a) Molybdenum is absorbed as molybdate by plants. It is involved in nitrogen metabolism including nitrogen fixation. It is a component of enzyme nitrogenase and acts as enzyme activator. Its deficiency causes chlorosis and necrosis, whiptail of cauliflower and premature leaf fall.
Copper is absorbed by the plant in ionic form. Its deficiency causes necrosis, dieback in Citrus, reclamation in legumes.
Manganese is absorbed by the plants as bivalent ion. It acts as enzyme activator. Its deficiency causes interveinal chlorosis as well as yellowing of starch and their subsequent degenerate.
Zinc is needed for biosynthesis of IAA and also acts as enzyme activator. Its deficiency causes chlorosis, little leaf, rosette, white bud of maize and mottling of leaves