Abstract
Oilseed rape (Brassica napus) is a Cadmium (Cd) hyperaccumulator. However, high-level Cd at the early seedling stage seriously arrests the growth of rape, which limits its applications. Brassica juncea had higher Cd accumulation capacity, but its biomass was lower, also limiting its applications. Previous studies have confirmed that Selenium (Se) can alleviate Cd toxicity. However, the regulatory mechanism of Se in different valence states of Cd accumulation was unclear. In this study, we investigated the ameliorating effects of three Se valence states, Na2SeO4 [Se(VI)], Na2SeO3 [Se(IV)] and Se-Met [Se(II)], to Cd toxicity by physiological and biochemical approaches in hydroponically-cultured Brassica juncea and Brassica napus seedlings. Although Se treatments slightly inhibited seedling Cd concentration, it tripled or quadrupled the Cd accumulation level per plant, because dry weight increased about four times more with Se and Cd application than with Cd treatment alone. Among the different valence states of Se, Se(II) had the most marked effect on reducing Cd toxicity as evidenced by decreased growth inhibition and Cd content. The application of Se(II) was effective in reducing Cd-induced reactive oxygen species accumulation, and promoted the antioxidant enzyme activity and photosynthesis of both Brassica species. In addition, Se(II) treatment increased the concentrations of Cd in the cell wall and soluble fractions, but the Cd concentration in the organelle part was reduced.
Highlights
Cadmium (Cd) is a trace heavy metal naturally present in soil
Growth obvious symptoms of Cd toxicity, such as leaf treatments.2.1.Under treatment, Brassica napus (BN) seedlings showed chlorosis and growth growthhigher inhibition was dramatically in Figure 1, the biomass Cd-induced of BN is significantly than that of Brassica juncea (BJ)
Relative to treatment with Se(IV) and Se(VI), the Se(II) treatment showed a more reduced after the application of Se, and the dry weight (DW) increased about one to four times, significantcompared increasewith in DW
Summary
Cadmium (Cd) is a trace heavy metal naturally present in soil. With the development of industries such as mining and smelting, Cd pollution has become increasingly serious [1]. A non-essential element of plants, has become a common pollutant in farmland soil environment. Cd ions in the soil are absorbed by the plant roots and transported to the leaves via symplast and apoplast transport [2]. Taken up in non-tolerable amounts, Cd causes growth inhibition and even death by deteriorating physiological processes, including biomass production, nutrient acquisition, antioxidant enzyme activities, and photosynthesis [3,4]. Appropriate fertilization, vacuolar sequestration, and adding exogenous ions might be effective in reducing Cd uptake and its accumulation in crops [5,6]
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