Reduction of cadmium toxicity in wheat through plasma technology

Abstract

Cadmium (Cd) contamination in plant-derived food is a big concern. This study examines whether and how Ar/O 2 and Ar/Air plasma techniques lead to Cd detoxification in wheat. Treatment with Ar/O 2 and Ar/Air changed the seed surface and decreased the pH of seeds as well as the cultivation media. Generally, plants subjected to Cd treatment from seeds treated with Ar/O 2 and Ar/Air plasma showed considerable progress in morphology and total chlorophyll synthesis compared to Cd-treated wheat, suggesting that plasma technology is effective for Cd detoxification. Furthermore, Ar/O 2 and Ar/Air plasma treated plants showed a significant decrease in root and shoot Cd concentration, which is consistent with the reduced expression of Cd transporters in the root ( TaLCT1 and TaHMA2 ) compared with the plants not treated with plasma in response to Cd stress. This Cd inhibition is possibly accomplished by the decrease of pH reducing the bioavailability of Cd in the rhizosphere. These observations are in line with maintenance of total soluble protein along with reduced electrolyte leakage and cell death (%) in root and shoot due to Ar/O 2 and Ar/Air treatments. Further, Cd-induced elevated H 2 O 2 or oxidative damage in tissues was mainly diminished through the upregulation of antioxidant enzymes (SOD and CAT) and their corresponding genes ( TaSOD and TaCAT ) induced by Ar/O 2 and Ar/Air plasma. Grafting results suggest that root originating nitric oxide signal possibly drives the mechanisms of Cd detoxification due to plasma treatment in wheat. These findings provide a novel and eco-friendly use of plasma technology for the mitigation of Cd toxicity in wheat plants.

Non-Thermal Plasma—A New Green Priming Agent for Plants?

“…In the first studies dedicated to the effect of NTP on plants, enhanced germination and growth parameters of treated plants were mostly observed. Effects of NTP were studied on many plant species–chicory [ 42 ], wheat [ 43 , 44 , 45 , 46 ], pepper [ 3 , 47 ], maize [ 36 ], pea [ 48 , 49 ], hemp [ 50 ], cucumber [ 3 ], oilseed rape [ 51 ], etc. Multiple works stated that there was no change in the final germination percentage, yet the germination speed was enhanced in NTP-treated seedlings [ 52 , 53 ].…”

“…Despite the minimal changes in CAT activity, the authors noticed that CAT isoenzyme expression showed significant changes in almost every group [ 68 ]. The importance of working gas for differences in the activity of antioxidant enzymes is illustrated in the study by Kabir et al [ 45 ]. They observed changes in antioxidant enzyme activity between NTP generated in Ar/O 2 and Ar/air mixtures.…”

“…NTP generated in Ar/O 2 induced an increment in SOD and ascorbate peroxidase (APX) activity, while no changes were found for Ar/air plasma. The pre-treatment of wheat seeds by Ar/O 2 plasma could even reverse the decrease in antioxidant enzymes activity caused by cadmium [ 45 ].…”

“…In addition to genes for antioxidant enzymes, two genes encoding cadmium transporters ( TaLCT1 and TaHMA2 ) have also been investigated. For both genes, cadmium caused their overexpression; however, if the seedlings were pre-treated by NTP, their expression was at the level of negative control, despite the presence of cadmium [ 45 ].…”

“…The impact of heavy metals on plants is well-known, and is a serious environmental problem, especially in mining areas. In the study by Kabir et al [ 45 ], cadmium caused deterioration in the growth parameters of wheat, a decrease in the amount of chlorophyll and soluble proteins, and, on the contrary, an increase in the amount of cadmium in the plant, as well as the amount of H 2 O 2 , expression of TaLCT1 , and TaHMA2 genes encoding cadmium transporters. Pre-treatment of seeds with NTP managed to ameliorate all these symptoms and also caused an increase in CAT and SOD activities, as well as an increase in expression of their genes.…”