Azelaic and pipecolic acids mitigate chromium toxicity in barley seedlings by maintaining redox and ion homeostasis and depriving Cr uptake.

The roles of pipecolic (Pip) and azelaic (AzA) acids in mitigating Cr-induced injury in plants remain uninvestigated, rendering their role somewhat mysterious. Chromium reduced seedling growth, photosynthetic pigments, nutrient uptake, and relative water content, and triggered oxidative bursts relative to nonpolluted seedlings. AzA or Pip spraying reversed Cr toxicity on growth while decreasing Cr bioaccumulation. Under normal or Cr-pollution conditions, spraying Pip and AzA increased photosynthetic pigments, chlorophyll stability index, nutrient uptake, and seedling development relative to untreated seedlings in those conditions. Furthermore, AzA or Pip spraying preserves redox homeostasis by boosting antioxidant solutes and antioxidant enzyme activity over untreated seedlings. Spraying Pip to Cr-affected seedlings significantly increased dry mass of shoots (72.50%) and roots (36.36%), total phenols (219.04%), and total chlorophyll (32.66%) over those treated with water. This increase was linked to a great reduction in H2O2 (31.22%), malondialdehyde (16.31%), membrane permeability (47.04%), and Cr uptake in shoots (39.08%) and roots (26.50%). Collectively, current outcomes highlight that Pip or AzA can mitigate Cr injury by strengthening antioxidant capacity, sustaining ion homeostasis, refining root structure, and reducing Cr bioaccumulation and translocation. Pip, as a novel molecule, may be favored over AzA for barley establishment in Cr-contaminated conditions.