Leaf infections: siderochromes (natural polyhydroamates) mimic the "green island" effect.
Topical application of as little as 5x10(-12) moles of pure siderochromes (polyhydroxamate iron-transport compounds from bacteria and fungi) onto detached bean leaves causes spots of chlorophyll retention that are surrounded by chlorotic halos. These spots appear similar to "green islands" that are caused by certain fungal infections on leaves and are somewhat similar to zones where senescence is delayed by cytokinin.
Atkin
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CL
Neilands
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JB