Give reasons for the following:
GeneralClass 12AllAnswered 27 Mar 2026
Answer
(i) Iron is not a constituent of chlorophyll but its deficiency causes chlorosis.
Answer: Though iron (Fe) is not a structural component of chlorophyll, it is essential for chlorophyll biosynthesis. Iron activates several enzymes involved in chlorophyll synthesis pathways. Therefore, iron deficiency impairs chlorophyll production, leading to chlorosis (yellowing of leaves).
(ii) Rhizobium can fix nitrogen only in the presence of leghaemoglobin.
Answer: The enzyme nitrogenase is extremely oxygen-sensitive and becomes inactivated in aerobic conditions. Leghaemoglobin acts as an oxygen scavenger, binding free oxygen and creating the strictly anaerobic environment necessary for nitrogenase to function efficiently in root nodules.
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