Assessment of zinc toxicity and tolerance in chickpea (Cicer arietinum L.) cultivars using physiological, biochemical and metabolomic responses

Background and Aims : Zinc (Zn) is an essential microelement that plants need for appropriate growth and development. However, high concentrations may hamper the physio-chemical and metabolic processes and weaken plant growth. This study aims to broadly explore the relative tolerance of chickpea ( Cicer arietinum L.) cultivars, and examine their physiological, biochemical, and metabolomics responses under various Zn levels. Methods : Three chickpea cultivars: ICCV89310 (IC8), NC234 (NC2), and ICCV89323-B (IC8-B) were exposed to different Zn levels (Ck, 50, 100, and 150 µM) for one week in a hydroponic medium. Growth and physiological indices, oxidative stress markers, antioxidant enzymes activity, and osmolytes content were detected. Primary metabolites profile and accumulation of Zn were assessed using GC-MS and ICP-OES, respectively. Results : IC8 and NC2 cultivars exhibited more tolerance than IC8-B because of their high biomass and plant height, root-to-shoot ratio, shoot water, and chlorophyll contents under high Zn stress. Besides, Zn contents were higher in the root of IC8-B, while IC8 and NC2 showed high accumulation in the shoot. Under Zn stress, there was an increase in the concentrations of hydrogen peroxide (H ₂ O ₂ ), malondialdehyde (MDA), and electrolyte leakage (EL). Additionally, Zn supplementation positively regulated the activities of superoxide dismutase (SOD), peroxidase (POD), and osmolytes (proline, soluble sugars, and total protein), but catalase (CAT) and glutathione reductases (GR) were differential in response to Zn stress. Simultaneously, metabolomics profiling revealed forty-six responsive metabolites in IC8, NC2, and IC8-B, mainly consisting of organic acids, amino acids, amines, alcohols, and sugars. Conclusion : Cultivars IC8 and NC2 displayed superior tolerance to Zn stress compared to IC8-B, showcasing robust growth characteristics and biochemical responses. The relative tolerance potential of IC8 and NC2 may be attributed to different adaptive strategies, such as a well-developed profile of responsive metabolites, such as histidine, asparagine, tryptophan, allantoin and antioxidants. Hence, cultivar IC8-B maybe utilized as a control cultivar under Zn stress to evaluate other chickpeas' tolerance capacity. Besides, IC8 and NC2 can be suggested as promising candidates for Zn-contaminated soil.