Abstract
The effects of K nutrition on polyamine content were analyzed in several parts of fruiting cuttings of Cabernet Sauvignon at different stages of development. Polyamines (especially conjugates and wall-bound forms) were strongly influenced by K nutrition in several organs before visual nutrient deficiency and excess symptoms appeared in leaves. These changes in polyamine composition and content induced by K nutrition differed according to tissue and stage of development. K deficiency and K excess (associated with Mg deprivation) had some opposite effects on polyamine metabolism, depending on tissue and stage of development. Accumulation of free putrescine in leaves coincided with the appearance of severe K deficiency symptoms. The visual appearance of Mg deficiency, induced by K excess, was associated with an accumulation of free spermidine, spermine, and diaminopropane in leaves. The results suggest that polyamines, especially conjugated and wall-bound polyamines, appear in some organs as good indicators of the K status of the grapevine and can be used as sensitive biochemical markers to distinguish the optimum K levels for grapevines before the appearance of K nutrient deficiency symptoms.
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