The Effect of Agmatine and Other Precursors on the Accumulation of Putrescine in Grape Leaves

Abstract

Feeding studies were conducted with healthy Thompson Seedless leaves using compounds that are known to be putrescine precursors in plants. Feeding agmatine or N-carbamoylputrescine caused accumulation of putrescine in the leaves whereas arginine did not lead to increased putrescine levels. Likewise, citrulline, ornithine, and N,N-dicarbamoylputrescine did not lead to increased putrescine. These results indicate that healthy leaves have the enzymes necessary to convert agmatine to putrescine. Free and conjugated putrescine was measured in Cabernet Sauvignon leaves with symptoms of potassium deficiency and compared to the levels in leaves without symptoms. Leaves with symptoms had 26 times more free putrescine than healthy leaves, but the amount of insoluble-conjugated putrescine was the same. Results also suggest that neither the healthy nor the potassium-deficient Cabernet Sauvignon leaves contained soluble-conjugated forms of putrescine. Insoluble-conjugated putrescine was not increased in healthy Thompson Seedless leaves fed either arginine or agmatine, despite a large increase in the free putrescine pool in the leaves given agmatine. It is concluded that the large increase in free putrescine seen in leaves suffering potassium deficiency, or in healthy leaves fed agmatine, does not lead to a change in the insoluble-conjugated putrescine.