Ammonium regulates redox homeostasis and photosynthetic ability to mitigate copper toxicity in wheat seedlings

As an essential plant micronutrient, copper (Cu) is required as a component of several enzymes, but it can be highly toxic to plants when present in excess quantities. Nitrogen (N) application can help to alleviate the phytotoxic effects of heavy metals, including Cu, and different N forms significantly affect the uptake and accumulation of heavy metals in plants. The aim of this study was to determine the effects of different N forms, i. e., ammonium (NH4+) and nitrate (NO3 ), on Cu detoxification in wheat seedlings. The inhibition of seedling growth under excess Cu was more obvious in wheat plants supplied with NO3 than in those supplied with NH4+. This growth inhibition was directly induced by excess Cu accumulation and reduced absorption of other mineral nutrients by the plants. Compared with seedlings treated with NO3 , those treated with NH4+ showed a decrease in Cu-induced toxicity as a result of increased antioxidant capacity in the leaves and a lower redox potential in the rhizosphere. Furthermore, treatment with NH4+ decreased the loss of mineral nutrients in wheat seedlings exposed to excess Cu. In conclusion, compared with supplying NO3 , supplying NH4+ to wheat seedlings under Cu stress improved their ability to maintain their nutritional and redox balance and increased their antioxidant capacity, thereby preventing a decline in photosynthesis. According to our results, NH4+ is more effective than NO3 in reducing Cu phytotoxicity in wheat seedlings.

Automated summary

This study investigated the effects of different nitrogen forms on copper detoxification in wheat seedlings, finding that seedlings supplied with nitrate experienced more growth inhibition under excess copper compared to those supplied with ammonium. Ammonium-treated seedlings showed increased antioxidant capacity and lower redox potential, leading to reduced copper toxicity and mineral nutrient loss. The results suggest that supplying ammonium is more effective than nitrate in reducing copper phytotoxicity in wheat seedlings.