Copper nanoflower priming mitigates lead (Pb) toxicity in chickpea (Cicer arietinum) by enhancing germination and antioxidant defence

Copper-based hybrid nanoflowers (Cu-HnF) and other plant nanomaterials provide an exciting avenue of research in agriculture, particularly in relation to stress alleviation. In this study, we evaluated Cu-HnF as a seed priming agent (10 and 20 mg/L) to ameliorate lead (Pb) toxicity (10 and 20 mM) associated with chickpea (Cicer arietinum). Response parameters (germination) and oxidative stress indicators (malondialdehyde - MDA), antioxidant enzyme activity, and expression of several stress-related genes were tested as part of our study. When exposed to lead (Pb), the germination response was reduced and MDA levels increased reflecting oxidative stress. However, Cu-HnF seed priming did improve germination for the Pb-stressed group seeds and did so while concomitantly reducing MDA levels when compared to lead treatment alone. Cu-HnF priming also produced an increase in the enzymatic activity of several antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) under stress subject to lead (Pb). In qRT-PCR analysis, Cu-HnF priming improved expression of respective SOD and CAT genes, which supported the activity of antioxidant enzymes observed with treatment. In summary, seed priming with Cu-HnF and potential for improved chickpea tolerance of Pb stress due to improved germination, less oxidative damage, as well as activation of antioxidant defense systems showed in both enzymatic and transcriptional levels. These results then point to the potential for seed priming with copper-based hierarchical nanoflowers to develop sustainable agricultural practices in areas impacted by heavy metal contaminants such as lead (pb). Keywords: Nanoflowers, Seed priming, Lead (Pb) toxicity, Oxidative stress, Antioxidant enzymes