Relation of Increased Potassium Nutrition to Photosynthesis and Translocation of Carbon

Effects of supplying K+ at 2 or 10 millimolarity concentration on net carbon exchange and translocation of products of photosynthesis were studied in plants of Beta vulgaris L. (var. Klein E). Transport of K+ into and out of leaves was studied with 42K over a 3-day period. Increasing the K+ supplied to the roots from 2 millimolarity, a level just sufficient to overcome obvious deficiency symptoms, to 10 millimolarity resulted in a gradual accumulation of K+ per unit area and an increased export of K+ to sink regions. No significant increase in net carbon exchange was observed in leaves that had accumulated a high level of K+per unit area. Initiation rate, total area, and total fresh weight of leaves of plants with K+ supplied at 10 millimolarity was similar to that for leaves from plants at a 2 millimolarity level. Shoot/root ratio and dry weight accumulation, which are indicative of translocation and partitioning over the long term, were independent of K+ supply in the 2 to 10 millimolarity range. Accumulation of K+ by exporting leaves and its subsequent recirculation to sinks increased when K+ supply was increased in this range but did not appear to affect carbon nutrition even after a long period