Iron uptake by plants from nutrient solutions with excess chelates in long term studies‐relationship with pe + ph

Abstract

Bush bean and corn plants were grown in nutrient solutions for 21 and 14 days respectively with CaCO₃ in the solution to give solution pH of near eight and mild iron deficiency. The bush beans were subjected to excess EDDHA and the com to excess EDTA. Excess EDDHA at 1000 and 100 μmolar resulted in increased Fe in leaves at both 10^‐7 and 10^‐6 M FeEDDHA and in some of the solutions concentration of Fe²⁺ would be less than 10^‐8 M if pe + pH were 6 or more. If pe + pH were more than 7, concentration of Fe²⁺ would be even less. Excess EDTA at 1000 and 100 ymolar resulted in no decrease of Fe in shoots of corn for 10^‐6 M Fe and the 100 resulted in a slight decrease at 10^‐7 M Fe on the per plant basis. Concentration of Fe²⁺ would be less than 10^‐8.8 and 10^‐7.8M respectively for 10^‐7 and 10^‐6 M Fe with the 1000 ymolar excess chelate. The pe + pH would be greater for corn than for bush beans because of less Fe stress response in corn. In another experiment where Fe was not deficient (pe + pH would then be higher), 100 μmolar excess DTPA resulted in increased Fe in bush bean plants grown for 18 days in nutrient solution for solution pH of both pH 4.3 and 7.6. Again concentration of Fe²⁺ would be 10^‐8 M or less with the excess chelate, yet uptake was greater than without the excess chelate where concentration of Fe²⁺ could be as much as 2 x 10^‐5 M especially at the pH of 4.3 (pe + pH would need to be less than 4).