Interaction of rubidium or sodium with potassium in absorption by intact sugar beet plants.

This study concerns the selective absorption of K and Rb or of K and Na by intact sugar beet (Beta vulgaris) plants from modified conventional nutrient solutions over an extended period of plant growth. Long term results agreed with those of short term experiments by other investigators using excised root systems and simple salt solutions. Potassium and Rb were mutually competitive in their absorption. High selectivity of K relative to Na absorption was observed. Sodium was excluded during the early growth period of sugar beets.

Sodium and rubidium as possible nutrients for sugar beet plants.

This study concerned the degree to which Na or Rb could substitute for K in the growth of sugar beet plants when K in the culture solution was low (1 meq/liter) or high (12 meq/liter).Sodium at high concentrations increased the growth of plants in a basal nutrient medium when either deficient in K or when adequately supplied with K alone. Redistribution of K from petioles to blades could not fully explain these results. Therefore, the essentiality of Na per se for growth of sugar beet plants may be inferred.Rubidium increased the growth of plants significantly when supplied in small doses to a nutrient medium deficient or adequately supplied with K. The amount of K added and the mode of Rb addition to solution cultures should be carefully considered when studying the effect of Rb on growth. High Rb concentrations were toxic, especially to the growth of fibrous roots.Sodium or Rb have been shown to enhance the growth of sugar beet plants under either low or high K conditions. Essentiality of either Na and/or Rb per se for growth of sugar beets may be inferred, but other criteria should be fulfilled also for conclusive proof.

Selenium nutrition of green plants. Effect of selenite supply on growth and selenium content of alfalfa and subterranean clover.

Alfalfa and subterranean clover plants were grown in highly purified nutrient solutions to which selenite selenium had been added at 0, 0.025, 0.25, 2.5 or 25.0 mug-atoms/liter. In both species, yields of tops and roots were significantly less at 25.0 mug-atoms/liter than at lower selenium concentrations (p < 0.01). The results indicated that growth was adversely affected when the concentration of selenium in mature leaf tissue reached 0.2 to 0.8 mug-atom/g dry weight.No beneficial effect of selenium was demonstrated on the growth of either species. If selenium is required by these species, the critical level will probably be below 0.001 mug-atom/g of dry plant material. Results are discussed in relation to earlier work on the selenium nutrition of plants.

Energy balancing in Nitella cells treated with dinitrophenol.

The toxic action of 2,4-dinitrophenol on the large cells of the alga, Nitella clavata, was evaluated, with the rate of protoplasmic streaming and the survival time at three light intensities used as criteria. At a sufficiently high intensity the cells survived several weeks, an indication that the energy-uncoupling action of dinitrophenol could be counterbalanced to some extent by an increased energy input. In the treated cells chloroplasts moved from the outer gel-type cytoplasm into the inner, streaming cytoplasm.