Varietal variation in uptake and utilization of potassium (rubidium) in high‐salt seedlings of barley

Seedlings of eleven varieties of barley (Hordeum vulgare L.) showed differences in utilization of K+ from a full nutrient solution containing 3.0 mM K+. The K+ content of both roots and shoots was proportional to the fresh weights and dry weights after a week in the nutrient solution. The K+ use‐efficiency ratio, which indicates the efficiency of nutrient utilization (mg dry weight produced per mg K+ absorbed), differed significantly among the varieties. There was no correlation between influx of Rb+ and the content of K+. It is suggested that there are wide varietal differences in such genetically‐determined properties as ion influx and efflux and net ion transport to the shoot. Further‐more, the influx of Rb+ was closely linked to transpiration, probably due to a variety‐specific non‐metabolic part of Rb+ influx. Varietal differences in influx of Rb+ were more pronounced in high‐K+ roots than in low‐K+ roots with maximum rate of Rb+ uptake, but the rank of varieties was the same in each case. – Criteria for the selection of K+ use‐efficient varieties of barley are discussed.