HYDROGEN ION CONCENTRATION IN RELATION TO ABSORPTION OF INORGANIC NUTRIENTS BY HIGHER PLANTS

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Abstract
As a part of a general investigation of the effects of H-ion on growth of higher plants, expts. were conducted on the relation of external pH to the absorption of Ca, Mg, K, nitrate and phosphate. Lycopersicum esculentum, Lactuca sativa and Cynodon dactylon were grown for 5 weeks in a complete nutrient soln. at a favorable pH, and were then placed for 96 hrs. in a series of nutrient solns. ranging, in gradations of 1 pH unit, from pH 3 to pH 9. In the entire range of pH, injury to roots was observed only at pH 3. At pH 3, no absorption, in fact indications of loss, of Ca and phosphate were in evidence. For Lycopersicum and Lactuca this pH was also wholly unsuited for the absorption of other ions. At pH 9 on the other hand, only the absorption of phosphate showed a marked decrease. Evidence was obtained of lower Ca absorption, particularly by tomato and lettuce, from strongly acid solns. (pH 4 and 5) than at higher pH values. No profound effects of external reaction between pH 4 and 9 on the absorption of Mg, K and nitrate were noted.