Differential response of Fe‐inefficient muskmelon, tomato, and soybean to phytosiderophore released by coker 227 oat

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Abstract
Several responses are induced in plants for the solubilization and uptake of iron (Fe) when they are subjected to Fe‐deficiency stress. Iron‐efficient Coker 227 oat (Avena byzantina C. Koch.) responds to Fe‐deficiency stress by producing a phytosiderophore which chelates Fe. Iron‐inefficient fefe muskmelon (Cucumis melo L.), T3238fer tomato (Lycopersicon esculentum Mill.), and T203 soybean (Glycine max (L.) Merr.) are dicotyledonous plants which do not respond to Fe‐deficiency stress and are therefore classed as Fe‐inefficient cultivars. This study was conducted to determine whether these Fe‐inefficient cultivars possess the ability to utilize Fe from a phytosiderophore produced by Coker 227 oat. These Fe‐inefficient cultivars were grown in a modified Steinberg solution with 1.2 mg L‐1 Fe and in either the presence or absence of oat. Iron solubilized by phytosiderophore was quantified in a separate study. Phytosiderophore released into solution was proportional to the number of oat plants in the treatment. The muskmelon and tomato plants grown in combination with oat had higher leaf Fe and lower Fe‐deficiency chlorosis than did plants grown alone. Conversely, soybean plants grown in solution with oat had lower leaf Fe and more severe Fe‐deficiency chlorosis than did plants grown alone. Iron‐inefficient fefe muskmelon and T3238fer tomato apparently possess unidentified mechanism(s) to obtain Fe from phytosiderophore released by oat, while T203 soybean is ineffective in obtaining Fe from the phytosiderophore complex.