Potassium Retranslocation in Seedlings of Hordeum Vulgare

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Abstract
Measurements have been made both on the uptake of potassium and potassium isotope from a nutrient solution and their redistribution within barley plants. During the experimental period the seedlings had three leaves which represented different stages in leaf development, i.e. from the mature to the rapidly developing stage. The results showed that substantial retranslocation of potassium within the plant took place. Trans-location was most evident in the mature leaf which exported at least 1.6 [mu]-equiv. per day but showed little potassium uptake. About 50% of the potassium taken up by the rapidly developing youngest leaf was shown to be derived from within the plant, the net uptake being 3.5 [mu]-equiv. per day. The movement of potassium within the plant is discussed in relation to known net movements of potassium. The mechanisms of potassium uptake by different leaves and its subsequent retranslocation are briefly considered. Possibilities of competition between different tissues are particularly emphasized.