Effects of Ultraviolet Radiation and Calcium and Their Interaction on Salt Absorption by Excised Mung Bean Roots.

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Abstract
The effects of Ca, ultraviolet radiation, dilute HC1 and NaCl solutions on salt absorption by excised mung bean roots (Phaseolus aureus) were investigated, using Rb86 and P32 as tracers. Both Rb and phosphate uptake were greatly enhanced by the presence of Ca. Short periods of pretreatment of excised roots with dilute HC1 and NaCl solutions increased subsequent Rb uptake but decreased phosphate absorption. The effects of HC1 and NaCl were reversed by Ca. Rb absorption was increased by ultraviolet radiation of 2537 A, but the presence of Ca during absorption drastically decreased Rb uptake by irradiated roots. Phosphate absorption by irradiated roots was reduced by ultraviolet radiation to a slight degree, and was further decreased by the presence of Ca ions. The results obtained have been interpreted as being due to the involvement of a ribonucleoprotein in salt absorption. The suggestion has been made that the nucleic acid binds cations, while the protein moiety binds anions.