Iron chlorosis in silver maple (Acer saccharum)

Abstract

Correctives for iron chlorosis have been applied to soil, sprayed on leaves and injected into woody plants. Some success in woody plants has been achieved from soil applied chelated Fe and injected Fe chelates. Silver maple has been unusual in that little response to chelated Fe was found. Experiments were devised to inject silver maples with different Fe chelate formulations, comparing results with a soil applied EDDHA treatment as well as chlorotic and green controls. Silver maple, for the most part, failed to respond to any of the chelate treatments applied. Foliar analyses revealed high levels of foliar Ca in chlorotic leaves compared to green leaves. When the soil producing green and chlorotic plants was analyzed, it was found that total soil Fe levels were higher for green control plants than chlorotic control plants. This increased level of total soil Fe was not reflected in the foliar analysis. There was no major distinction in foliar Fe levels between green and chlorotic tissue. Xylary sap pH and Eh were also recorded for silver maples growing in various solution cultures. Solution cultures were prepared to simulate various types of Fe stress capable of causing Fe chlorosis. Although the solution culture pH varied widely, xylary pH stayed relatively constant. Xylary Eh measurements maintained an even narrower "buffered" range. When pH and Eh were combined on a similar scale (pH+ pe), the xylary sap pe + pH was observed to stay in a narrow range even when solution pe + pH varied widely.