Changes in organic, mineral and photosynthetic metabolism during senescence of leaves of pigeonpea (Cajanus cajan L. Millsp.) were investigated. It was found that the senescent leaves contain less carbohydrates and proteins while elements like potassium and phosphorus are withdrawn from them. This element withdrawal was associated with accumulation of calcium, iron and manganese. This imbalance of inorganic nutrients possibly disturbs the normal metabolism in the senescent leaves which result in considerable loss in photosynthetic activity. It can also be attributed to the disturbed chloroplast structure in senescent leaves. In the senescent leaves, accumulation of amino and organic acids was increased, while the synthesis of sugars was depressed. The physiological significance of this disturbed metabolism is discussed.
