Adaptive strategies of Parietaria diffusa (M.&K.) to calcareous habitat with limited iron availability *

The study of native plants growing in hostile environments is useful to understand how these species respond to stress conditions. Parietaria diffusa (M.&K.) is able to survive in highly calcareous soils and extreme environments, such as house walls, without displaying any chlorotic symptoms. Here, we have investigated the existence of Strategy I complementary/alternative mechanism(s) involved in Fe solubilization and uptake and responsible for Parietaria 's extraordinary efficiency. After assessing the specific traits involved in a calcicole‐behaviour in the field, we have grown plants in conditions of Fe deficiency, either direct (−Fe) or induced by the presence of bicarbonate (+FeBic). Then, the growth performance, physiological and biochemical responses of the plants were investigated. The study shows that in Parietaria +FeBic, the classical responses of Strategy I plants are activated to a lower extent than in −Fe. In addition, there is a greater production of phenolics and organic acids that are both exuded and accumulated in the roots, which in turn show structures similar to ‘proteoid‐like roots’. We suggest that in the presence of this constraint, Parietaria undergoes some metabolic rearrangements that involve PEP‐consuming reactions and an enhancement of the shikimate pathway.