Labile anion binding by roots of two plum clones

The anion-exchange capacities (AEC) of roots of intact plants of two plum clones [Marianna 2624 (Prunus cerasifera × P. munsoniana) and Myrobalan 3-J (P. cerasifera)] were assessed with an anionic dye, eosin Y. The positively charged eosin-specific adsorption sites were metabolically dependent and also affected by nutrient status. Myrobalan 3-J roots adsorbed twice as much exchangeable NO₃ as did Marianna 2624. Since we previously showed that net nitrate uptake by Myrobalan 3-J persisted at half the ambient nitrate concentration as that characteristic of Marianna 2624, the data provide circumstantial support for a functional role of labile anion binding in active uptake at dilute concentrations of ambient nitrate.