Ion Absorption by a Woody Plant with Episodic Growth

Rooted cuttings of Euonymus japonica Thunb. were grown in solution culture for 3 months and rates of NO 3 - , Ca 2+ , K + , and Mg 2+ absorption were measured by their disappearance from solution. During shoot elongation, absorption rates for these ions declined and the pH of the nutrient solution decreased to about 4. As a flush of shoot elongation ended, the absorption rates for the ions rose to much higher levels and the pH of the nutrient solution increased to 6 or above. The changes in the nutrient solution pH appear to be caused by changes in the relative cation-anion absorption.