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Abstract
Chlorotic silver maple (Acer sacoharinum L.) trees growing in a high pH soil were pressure injected with 1800 ml of a 1.0% (w: w) solution of ferrous sulfate. Net photosynthesis (Pn) of treated branches increased to at least eight times that of the control within two weeks after injection. Chlorophyll in treated branches also increased rapidly for the first two weeks after injection, and leveled off between 2.0–2.5 mg g‐1 fresh weight. Net photosynthesis for leaves in the shade was greater in treated than in control branches. Stomatal diffusive resistance was greater in the control than in Fe‐treated branches for both shade and full sun leaves. Foliar Fe concentration increased dramatically two days after injection, then decreased gradually to levels near the control as the season progressed. Injection of ferrous sulfate solution seems to activate and maintain chlorophyll biosynthesis for at least two growing seasons even though there does not seem to be a relationship between total Fe and chlorophyll.