Abstract
Kentucky bluegrass (Poa pratensis L.), a turf grass species that is hypertolerant of cadmium (Cd), is a potential phytoremediation material for soil polluted with Cd. However, the mechanism of Cd phytotoxicity in Kentucky bluegrass is unclear. Here, we compared the phenotype, induction of oxidative stress, and structural and non-structural carbohydrate contents between a Cd-tolerant genotype (‘Midnight’, M) and Cd-sensitive genotype (‘Rugby’, R). The results showed that both genotypes accumulated more Cd in the roots, whereas the R genotype distributed more Cd into the leaves compared with the M genotype. In both genotypes, Cd inhibited the length and fresh weight of the leaves and roots; increased the peroxidase (POD) activity but inhibited ascorbate peroxidase (APX) and catalase (CAT) activity; and increased the superoxide radical (O2−), hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents. However, the M genotype exhibited lower root length inhibition, and the H2O2 and MDA contents confirmed that the M genotype had increased Cd accumulation and resistance, while the R genotype exhibited a better distribution of Cd. Moreover, Cd stress significantly increased the soluble sugar, trehalose, and sucrose contents of both genotypes. Pectin, lignin, and cellulose were significantly increased to prevent the entry of Cd into the roots. The Cd-induced growth inhibition and physiological responses in Kentucky bluegrass were preliminarily explored herein, with the chelation of pectin, lignification, and antioxidant response being possible contributors to Cd detoxification in Kentucky bluegrass. In addition, the Cd-induced increase in trehalose, sucrose, and soluble sugar contents might play a pivotal role in the defense against Cd stress in Kentucky bluegrass.
Highlights
It is reported that low concentrations of Cd facilitate growth, and high concentrations can lead to wilting, chlorosis, and the inhibition of plant growth [7]
We identified a Cd-tolerant genotype ‘Midnight’ (M) and Cd-sensitive genotype ‘Rugby’ (R), and we used RNA sequencing technology to elucidate the molecular mechanisms through which these genotypes respond to 1000 μM Cd stress over 24 h [27]
The M genotype accumulated more Cd in the roots compared with R (Figure 1A)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Human activities and natural elements such as mining, waste gas emission, wastewater irrigation, and volcanic eruptions have resulted in severe heavy mental pollution in recent years [1]. Heavy metal in the soil poisons plants and accumulates through food chains [2]. Cd is the main pollutant present in the environment [3]. It accumulates in plants and is transmitted to other animals through ingestion [4]. Excess Cd causes chronic intoxication of the human body, giving rise to kidney injury and skeletal lesions [5,6]. The environmental problems caused by Cd pollution are a serious threat to human development.
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