Allocation of Fe and ferric chelate reductase activities in mesophyll cells of barley and sorghum under Fe-deficient conditions

Although the photosynthetic apparatus requires large amounts of Fe, the adaptive mechanisms of mesophyll cells for Fe acquisition under Fe-deficient conditions are unknown. Barley and sorghum, which are tolerant and susceptible to Fe deficiency, respectively, have similar Fe and chlorophyll contents in their leaves. However, the Fe-deficient barley photosynthetic apparatus was functional while that of sorghum was not. We show that barley preferentially allocates Fe to thylakoid membranes under Fe-deficient conditions. On the other hand, in sorghum, the proportion of leaf Fe allocated to thylakoids was not altered by Fe deficiency. The relationship between the maintenance of photosynthesis and light-dependent ferric chelate reductase activity on plasma membranes and chloroplast envelopes is also discussed.

► Fe-deficient barley and sorghum leaves had similar Fe and chlorophyll contents.
► The Fe-deficient barley photosynthetic apparatus was functional, but that of sorghum was not.
► The allocation of Fe to thylakoids increased in barley, but not in sorghum as a result of Fe deficiency.
► The decrease in FCR activities per protoplast caused by Fe deficiency was smaller in barley than in sorghum.