Interactions of rubidium, sodium, and potassium on the nutrition of sugar beet plants.

The effect of Rb on the growth and the development of sugar beet plants (Beta vulgaris, var. MS NB1 x NB4) depends on the Rb concentration, the K supply, and the relative abundance of Na. Rubidium added either to a low or high K solution with or without added Na increased leaf blade size greatly, possibly through an effect on phytohormones or through a "partitioning effect" on the distribution of carbohydrates, with top growth favored over storage roots.Sodium increased the growth of sugar beet plants when they were either K-deficient or adequately supplied with K. Sodium or Rb added to a high K solution increased the sucrose percentage and total sucrose of the storage roots significantly. Sodium and Rb supplied simultaneously to the nutrient solution resulted in synergetic effects only at low K supply.Potassium was translocated in mature leaves from the petiole to the blade when Na was added to a low K solution, or when Rb was added either to a low or a high K solution. Rb + K had little to no effect on Na redistribution.