Abstract
This study was aimed to explore that effects of Sb on physiological parameters of Acorus calamus and the possibility of using A. calamus as a remediation plant. A. calamus potted experiments were conducted using different concentrations (0, 250, 500, 1000, and 2000 mg/kg) of antimony potassium tartrate (Sb3+) (marked as CK, T1, T2, T3, and T4, respectively) and potassium pyroantimonate (Sb5+) (marked as CK, T′1, T′2, T′3, and T′4, respectively). The effects of Sb stress (Sb3+ and Sb5+) on leaf photosynthetic pigments, biomass, photosynthetic characteristics and chlorophyll fluorescence parameters of potted A. calamus were studied. With the rise of Sb3+ concentration from T1 to T4, the leaf pigment contents (chlorophyll a, b, carotenoid), plant height, dry weight, net photosynthetic rate (Pn), stomatal conductance (Gs), evaporation rate (E), PSII maximum photochemical efficiency (Fv/Fm), and PSII electron transfer quantum yield rate (ΦPSII) of A. calamus all reduced, while intercellular CO2 concentration (Ci) significantly increased. The reduction of Pn was mainly induced by non-stomatal limitation. Chlorophyll a/b ratio increased significantly versus the control, while carotenoid/chlorophyll ratio (Car/Chl) first decreased and then increased. The leaf Chl a, Chl b, Car, plant height, dry weight, Pn, Gs, E, Fv/Fm, and ΦPSII all maximized in T′1 (250 mg/kg), but were not significantly different from the control. As the Sb5+ concentration increased from T′2 to T′4, the above indices all decreased and were significantly different from the control. Moreover, intercellular CO2 concentration (Ci) decreased significantly. The reduction of Pn was caused by non-stomatal limitation, indicating the mesophyll cells were damaged. The Car/Chl ratio was stable within 0–500 mg/kg Sb, but decreased in T3 and T4, and rose in T′3 and T′4. After Sb3+ and Sb5+ treatments, translocation factor varied 19.44–27.8 and 19.44–24.86%, respectively. In conclusion, different form Sb3+ treatment, Sb5+ treatment showed a Hormesi effect, as low-concentration treatment promoted A. calamus growth, but high-concentration treatment inhibited its growth. The two forms of Sb both caused unfavorable effects on A. calamus, but the seedlings did not die and were modestly adaptive and Sb-accumulative. A. calamus, which is easily maintained and cultivated, can serve as a good candidate for phytoremediation of water contaminated with Sb.
Highlights
Antimony (Sb) is a ubiquitous trace element in the environment and a global pollutant and has been included as a priority pollutant by United States Environmental Protection Agency owing to its latent toxicity and carcinogenicity (Liu et al, 2013; Corrales et al, 2014)
Compared with CK, the contents of leaf chlorophylls a, b, and a + b (Chl a, Chl b, and Chl a+b), and carotenoid (Car) all significantly decreased after Sb3+ treatments (T1, T2, T3, and T4) and were all negatively correlated with the Sb3+ concentrations
Chlorophylls are an important type of pigments needed by plants for photosynthesis and participate in optical energy absorption, transfer and conversion during photosynthesis
Summary
Antimony (Sb) is a ubiquitous trace element in the environment and a global pollutant and has been included as a priority pollutant by United States Environmental Protection Agency owing to its latent toxicity and carcinogenicity (Liu et al, 2013; Corrales et al, 2014). The soil Sb concentrations in a Sb mining area of Italy were 19–4400 mg·kg−1, and the root Sb concentrations of Pistacia lentiscus were 0.46–22.3 mg/kg (Cidu et al, 2014). The soil and plant Sb concentrations in a tin deposit mountain of Hunan, China, were 10–2159 and 143.7 mg·kg−1, respectively (Wang et al, 2010; He et al, 2012), which interfered with plant growth and human health (Liu et al, 2010; Fu et al, 2011; Li et al, 2017).
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