Aluminum stress inhibits root growth and alters physiological and metabolic responses in chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) roots were treated with aluminum (Al3+) in calcium chloride (CaCl2) solution (pH 4.7) and growth responses along with physiological and metabolic changes were investigated. Al3+ treatment for 7d resulted in a dose dependent decline of seed germination and inhibition of root growth. A significant (p ≤ 0.05) decline in fresh and dry biomass were observed after 7d of Al3+ stress. The root growth (length) was inhibited after 24 and 48 h of stress imposition. The hydrogen peroxide (H2O2) levels increased significantly (p ≤ 0.05) with respect to control in Al3+ treated roots. The hematoxylin and Evans blue assay indicated significant (p ≤ 0.05) accumulation of Al3+ in the roots and loss of plasmamembrane integrity respectively. The time-course evaluation of lipid peroxidation showed increase in malondialdehyde (MDA) after 12, 24 and 48 h of stress imposition. Al3+ treatment did not alter the MDA levels after 2 or 4 h of stress, however, a minor increase was observed after 6 and 10 h of treatment. The proton (1H) nuclear magnetic resonance (NMR) spectrum of the perchloric acid extracts showed variation in the abundance of metabolites and suggested a major metabolic shift in chickpea root during Al3+ stress. The key differences that were observed include changes in energy metabolites. Accumulation of phenolic compounds suggested its possible role in Al3+ exclusion in roots during stress. The results suggested that Al3+ alters growth pattern in chickpea and induces reactive oxygen species (ROS) production that causes physiological and metabolic changes.