Thin stems - lateral stems affected, not terminal. Exceptions, e.g., crucifereae. Fe Immobile Component or co-factor for many oxidases. Possible precursor of Mg in chlorophyll. Interveinal chlorosis of younger leaves.
Larger veins remain green.
May substitute for Mg in some reactions. Interveinal chlorosis of younger leaves. Scallop leaf edges. Die back of tips of stems. Chlorosis of younger leaves.