Alleviation Of Cadmium-Induced Oxidative Damage In The Seedling Roots Of Medicago Sativa By Hydrogen-Rich Water

Cadmium (Cd), one of the most extremely toxic heavy metals, has become a major environmental pollutant in recent years. Cd is easily accumulated by higher plants because of similarity with other essential elements, thus bringing about dramatically grave inhibition of the higher plant photosynthetic, respiratory and nitrogen metabolisms. Subsequently, the typical phenotype of Cd toxicity, including the stunt of plant growth, etiolation, mortification et al. and even cell death are observed.Hydrogen is a colourless, odourless, non-metallic, tasteless and highly combustible diatomic gas. Recent studies revealed that hydrogen gas (H2) is a vital physiological regulatory molecule with antioxidant and anti-inflammatory better protective efficacy on animal cells and organs. There is also adequate experimental evidence showed that H2 could bring about plant tolerance to some abiotic stresses. However, the role of H2 in cadmium (Cd)-induced stress amelioration is largely unknown. To elaborate the roles of hydrogen on relieve cadmium toxicity. Here, pretreatment with hydrogen-rich water (HRW) was used to characterize physiological roles and molecular mechanisms of H2 in the alleviation of Cd toxicity in Alfalfa plants. The results in this paper revealed that:1. The effect of HRW pretreatment on cadmium toxicity of Medicago sativa is dose-dependently, of which, the effect of 10% pretreatment is the most obvious in present study. The results demonstrate that pretreatments with different concentrations of HRW (1, 10,50 and 100%) lead to the improvement of the fresh weight by 4.4,20.1,16.8, and 11.1% in root tissues with respect to Cd stressed alone plants. Further experiments showed that, compared with the Cd treatment alone, the addition of HRW produced a similar dose-dependent reduction in the amount of TBARS as was found for seedling root growth.2.10% HRW could stunt the emergence of Cd toxicity phenotypes, including the improvement of root elongation and seedling growth. These responses were related to a significant increase in the total or isozymatic activities of representative antioxidant enzymes, or their corresponding transcripts. By contrast, when 10%HRW was pretreated, it significantly alleviated the effects of Cd on SOD and APX activities, being 60.2,25.1% higher, respectively, than those with Cd treatment alone. Which was consistent with a significant enhancement of the ratio of reduced/oxidized (homo)glutathione ((h)GSH).3. The experimental result of histochemical analyses suggested that ROS accumulation compared to Cd-free control samples, While 10% HRW pretreatment inhibits the root cells against Cd-induced oxidative stress.4. Plants pretreated with 10% HRW accumulated less amounts of Cd. The Cd content in HRW-pretreated root tissues was 29.4 and 22.9% lower than that of Cd-stressed alone sample.Together, this study revealed that H2 could reduce Cd uptake, suppresses ROS production and alleviates Cd-induced oxidative stress in plants by re-establishing redox homeostasis, therefore the usage of HRW could be an effective approach for Cd detoxification and could be explored in agricultural production systems.