Inactive iron in sugarcane leaves and its influence on enzymatic reactions and chloroplast metabolism

Iron chlorosis is a wide spread nutritional disorder in the sugarcane growing parts of Western India and results in serious economic losses. It appears that the iron in the chlorotic leaves is physiologically inactive which is probably due to higher P/Fe ratio. This immobilized iron lowers the activities of enzymes in which iron is involved and also disturbs the synthesis of other specific enzyme proteins some of which are stimulated while others are inhibited. The calculated active iron derived from the formula of De Kock et.al. (1979) shows a significant relationship of the active iron contents and the chlorophyll levels in the leaves. The inactive iron not only affects the quantity of chlorophylls but the quality also. As the chlorosis becomes severe the chlorophyll a/b ratio increases. Chlorosis is probably due to the inhibited synthesis of photosynthetic units, whose number is significantly lowered in the leaves as the degree of chlorosis increases. Mesophyll cell chloroplasts are more affected than the bundle sheath cells.