Abstract
Heavy metals negatively affect soil quality and crop growth. In this study, we compared the tolerance of six ryegrass cultivars to cobalt (Co2+), lead (Pb2+), and nickel (Ni2+) stresses by analyzing their physiological indexes and transcript levels of genes encoding metal transporters. Compared with the other cultivars, the cultivar Lm1 showed higher germination rates and better growth under Co2+, Pb2+, or Ni2+ treatments. After 48 h of Co2+ treatment, the total antioxidant capacity of all six ryegrass cultivars was significantly increased, especially that of Lm1. In contrast, under Pb2+ stress, total antioxidant capacity of five cultivars was significantly decreased, but that of Lm1 was unaffected at 24 h. Staining with Evans blue dye showed that the roots of Lm1 were less injured than were roots of the other five ryegrass cultivars by Co2+, Pb2+, and Ni2+. Lm1 translocated and accumulated lesser Co2+, Pb2+, and Ni2+ than other cultivars. In Lm1, genes encoding heavy metal transporters were differentially expressed between the shoots and roots in response to Co2+, Pb2+, and Ni2+. The aim of these researches could help find potential resource for phytoremediation of heavy metal contamination soil. The identified genes related to resistance will be useful targets for molecular breeding.
Highlights
Heavy metals come from both the natural environment and human activities [1]
The total antioxidant capacity of the six cultivars was increased in response to Co treatments (Figure 5a), decreased in response to Pb treatments (Figure 5b), and unchanged by Ni treatments (Figure 5c). These findings indicated that the ryegrass cultivars might be tolerant to Co but sensitive to Pb
Seed germination is a prerequisite for plant survival under stress conditions
Summary
Heavy metals come from both the natural environment and human activities [1]. Common heavy metals are not naturally degraded and accumulate continuously in the environment. They pose a serious threat to human health and food security [4,5]. Some heavy metals such as cobalt (Co), nickel (Ni), manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe) are essential micronutrients for plants. Nickel is an essential microelement for plant growth and development It is a component of several enzymes (e.g., glyoxalase and urease) required for nitrogen metabolism, and plays an important role in nitrogen assimilation. Excess Ni can reduce the seed germination rate, negatively affect photosynthesis and respiration, and cause yellowing and necrosis of the leaves [10]
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