Elucidating the Mechanistic Role of Zinc-Lysine to Enhance Cd Tolerance in Diverse Wheat ( Triticum aestivum L.) Cultivars Through Distinct Morpho-Physio-Biochemical Improvements Under Cd Stress

Purpose of the current study was to evaluate protective role of zinc-lysine (Zn-Lys) as seed priming agent at early growth stage of two diverse wheat cultivars in soil system. Wheat seeds [cv. Galaxy-2013 (V 1 ) and cv. Punjab-2011 (V 2 )] were primed with zinc-lysine solutions; 0, 0.5, 1, and 1.5 ppm for 14 h and grown in soil filled pots with four levels of Cd (0, 15, 30, and 45 μM) provided through Hoagland nutrient solution. The experiment was performed under natural environmental conditions with three replicates per treatment at Botanical garden of Government College University, Faisalabad, Pakistan. Cadmium toxicity caused a significant reduction in plant growth, chlorophyll, carotenoid, flavonoid, phenolic, protein contents, and lysine concentration irrespective of wheat cultivars. Likewise, Cd decreased nutrient acquisition predominantly in V 2 . Furthermore, increasing Cd stress significantly escalated anthocyanins, total soluble sugars, reducing sugars, total free amino acids, and enzymatic antioxidants in V 1 as compared to V 2 . However, using Zn-Lys as a seed priming agent improved nutrients uptake, chlorophyll synthesis, and biomass accumulation while diminishing the Cd uptake, which circumvented Cd toxicity by lowering oxidative stress and strengthening the antioxidant defense system in a dose dependent and cultivar specific manner. Treatment level of 1.5 ppm Zn-Lys (Zn-Lys3) proved more efficient and V 1 performed better than V 2 under Zn-Lys application and Cd stress. The current study provides detailed physiological insights towards understanding role of Zn-Lys in Cd tolerance in wheat cultivars differing in Cd tolerance. Significant correlations recorded between Cd uptake and wheat growth attributes while Zn-Lys application correlated with augmented growth of both wheat cultivars; therefore, it was inferred that Zn-Lys can reduce the adverse effects of Cd on growth of wheat and can be successfully used as an amino-chelated fertilizer. Wheat cultivation in Cd-polluted areas can be facilitated through use of chelated fertilizers (as seed priming agents) to minimize the adversative effects of Cd on food crops and to inhibit Cd entry into food chain. Graphical Abstract