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Ion Absorption by Corn Roots as Influenced by Moisture and Aeration¹

ABSTRACT

Using short-term experiments, the uptake by corn seedlings of Rb⁸⁶ from soil and from osmotic solutions has been measured under various levels of moisture stress and oxygen pressure. Soil moisture tensions, up to 12 atm., were developed using pressure plate apparatus appropriate to the tensions desired, and the osmotic studies were conducted with a highly porous, expanded perlite material wetted with aqueous solutions of mannitol. Continuous flushing with gas mixtures of air and nitrogen was used to maintain the oxygen partial pressures desired.

Moisture stresses developed from soil moisture tensions and from osmotic solutions differed markedly in their effect on Rb⁸⁶ absorption. The ion uptake decreased rapidly with initial increases in soil moisture tension and leveled out at higher tensions to give a curve nearly logarithmic in nature. Increasing osmotic pressure caused only a slight decrease in absorption of Rb⁸⁶ by the corn seedlings. The ion uptake from soil was nearly a straight line function of moisture content.

Initial increases in oxygen concentration of the gaseous environment at each level of soil moisture tension or osmotic pressure resulted in increased uptake of Rb⁸⁶. In soil, however, the minimum oxygen content at which ion absorption reached a level value decreased with increasing soil moisture tension.

¹ Part of a thesis submitted in partial fulfillment of the requirements for the Ph.D. degree at the Univ. of Illinois by the senior author and presented before Div. I and VI, Soil Science Society of America, Davis, Calif., Aug. 18, 1955.

² Former Graduate Assistant in Agronomy, Univ. of Illinois, now Assistant Agronomist, Colorado Agr. Exp. Sta.; and Head, Agronomy Dept., Univ. of Illinois, respectively.

Received for publication October 17, 1955. Accepted for publication July 23, 1956.