THE INFLUENCE OF CALCIUM ION ACTIVITY IN WATER CULTURES ON THE INTAKE OF CATIONS BY BEAN PLANTS.

Abstract

It is becoming increasingly evident that the adverse effect of alkali soils (14) on plant growth is due in part to the decreasing availability of calcium associated with increasing proportions of sodium upon the exchange complex of the soil. Ratner (12) presents data to show that a given level of adsorbed Ca is less exchangeable in the presence of adsorbed Na than when H, Mg, and ? are the complementary cations adsorbed. His evidence indicates (11, 13) that the energy of retention of Ca by soil colloids is sufficiently high in the presence of a relatively high level of adsorbed Na to prevent not only the intake of Ca by the plant but to actually remove Ca from the plant with the resultant death of the plant tissues from Ca starvation. He observed (12) that wheat seedlings failed to take in calcium from soil with an exchangeable-sodium percentage of 40. Van Itallie (16) found that growth of Italian rye grass was impaired by an exchangeablesodium-percentage in the soil of 26 and prevented by one of 50. Thorne (15) observed that the ability of tomatoes to take in calcium was reduced when the exchangeable-sodium-percentage was 40 or higher. Bower and Wadleigh (3) employed cultures with nutrients adsorbed on ion-exchange resins (1) to ascertain the nutritional effects of varying exchangeable-sodium-percentages on growth and cation accumulation by four species of plants. They found that different species varied widely in their response to increasing proportions of adsorbed sodium on the cation exchange complex. Dwarf red kidney beans were especially sensitive to this condition. Increasing exchangeable-sodium-percentages, with concomitantly decreasing exchangeable calcium and magnesium percentages, were effective in inducing marked decreases in the accumulation of Ca and Mg in tops and increases in sodium accumulation. However, the most striking effect of the substrates upon cation accumulation was found in the roots. The content of Ca and Mg per unit weight of root tissue was constant for ? Contribution from the U. S. Regional Salinity and Rubidoux Laboratories, Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, U. S. Dept. of Agriculture, Riverside, Calif., in cooperation with the eleven western states and the Territory of Hawaii. 2 Principal Chemist and Soil Scientist, respectively.