Foliar Applied Nickel on Buckwheat (Fagopyrum esculentum) Induced Phenolic Compounds as Potential Antioxidants

In this study, Fagopyrum esculentum (common buckwheat) sprayed with nickel (Ni) (0, 0.5, 1.0, 3.0, and 5.0mM) for different duration has been investigated for Ni accumulation, malondialdehyde (MDA), total phenolics, and phenolic acids. Ni accumulation significantly increased in dose-dependent manner. Plants exposed for 72h, showed visible damages as chlorosis and irreversible necrosis. The MDA and total phenolic contents increased at 24h of Ni treatments. HPLC data revealed that phenolic acids are in good correlation with concentration and durations of treatments. After 24 and 48h the contents of chlorogenic, p-hydroxybenzoic, hesperetic, p-anisic, and caffeic acids increased in Ni treated leaves. On the other hand, p-hydroxybenzoic, hesperetic, p-anisic, p-coumaric, caffeic acids contents decreased after 72h of Ni exposure. Vanillic and cinnamic acid followed same pattern and increased significantly at 3.0 and 5.0mM after 48h of Ni exposure. It may suggest that buckwheat can be possible hyperaccumulators of Ni, because of high Ni accumulation in tissues through foliar treatment. Furthermore, the analyzed phenolic acids have potential role as antioxidants, which provide tolerance to buckwheat against Ni treatment.