Exogenous IAA application alleviated altered physiological and biochemical processes through promoting H-ATPase and Fe chelate reductase activities in common bean (Phaseolus vulgaris L.) subjected to iron deficiency.

Iron deficiency is a common nutritional disorder observed in calcareous soils, where its resolution by classical methods has shown its failure. However, the exploitation of certain potentialities possessed by crops (rhizosphere acidification, H-ATPase; Fe chelate reductase, FeCR, etc.), and the use of some biostimulants remains most efficient and sustainable approach. A greenhouse experiment was conducted on common bean plants subjected (FeD), or not (control, C) to Fe deficiency, or subjected to Fe deficiency and sprayed with 1 mM indole-3-acetic acid (FeD-IAA). The key physio-biochemical traits developed by plants in the different treatments, and their interrelationships were analysed. Iron deficiency induced specific Fe chlorosis, reduced chlorophyll and disrupted photosystem II performance. Plant growth and Fe concentration also significantly decreased, despite the stimulation of H-ATPase and FeCR activities. However, exogenous IAA application alleviated the adverse effects of FeD, particularly through promoted H-ATPase and FeCR activities, and Fe2+ concentration. The polar transport of IAA promoted root growth, H-ATPase and FeCR activities under FeD. The resulted Fe promotes chlorophyll biosynthesis and photosynthetic functioning. The calculated rhizosphere acidification capacity (RAC) and Fe chelate reductase capacity (FeCRC) are two useful traits for tolerant plant screening. The exogenous IAA application is a useful, efficient and eco-friendly approach for Fe-chlorosis alleviation. It promotes soil quality through the improvement of the soluble, plant-available form of iron.