Metabolic changes in iron-stressed dicotyledonous plants

The response to iron deficiency stress in dicotyledonous plants is by far more complex than the simple activation of the reduction-based mechanism. In most of the Strategy I plants studied so far there is an associated increase in the activity of a plasma membrane H+-ATPase which actively extrudes the protons necessary both for decreasing the rhizospheric pH and generating the electrochemical proton gradient needed to drive ion uptake. Along with these activities, localised on the root plasma membrane, it has been found that metabolism is involved in sustaining the production of reducing equivalents [NAD(P)H] and ATP. Many processes (glycolysis, respiration, etc.) are increased to efficiently sustain the response to iron depletion. In particular, the activity of phosphoenolpyruvate carboxylase is increased several fold. These increases could be linked to the production of substrates for the ferric chelate reductases and H+-ATPase activities, generation of H+ for the cytosolic pHstat and organic acids. The activation of all these processes makes plants more efficient in the acquisition of iron.