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  • Author or Editor: Guoliang Han x
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The structure and chemical properties of strontium and calcium are similar. To study the interplay between calcium and strontium in plants, different concentrations of SrCl2 (0, 1, 4, and 10 mmol·L−1) were added to the Hoagland nutrient solution with 4 mmol·L−1 Ca2+ (normal level Ca2+) or 0.4 mmol·L−1 Ca2+ (low-level Ca2+), which were used to cultivate Chinese cabbage seedlings. Under the low-level calcium condition, strontium not only did not promote the growth of Chinese cabbage but showed more severe toxicity compared with that under the normal calcium condition. Under normal calcium condition, although the growth of Chinese cabbage was significantly inhibited by 4 mmol·L−1 strontium, strontium did not show significant toxicity. However, under the low-level calcium condition, 1 mmol·L−1 strontium caused a significant decline of plant biomass and photosynthetic activity. Sr2+ showed a competitive inhibitory effect on the absorption of Ca2+, and strontium was more easily absorbed by Chinese cabbage. Under the low-level calcium condition, strontium aggravated the inhibition of calcium absorption. The inhibitory effect of strontium on plant growth was significantly related to the calcium content in Chinese cabbage. Strontium cannot replace the function of calcium in plants under calcium-deficient conditions.

Open Access

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is one of the most toxic polybrominated diphenyl ethers (PBDEs). The toxic effects of BDE-47 on Chinese cabbage seedlings were analyzed in this study. After a 30-day hydroponic exposure to BDE-47 at different concentrations (25, 50, 75, and 100 µg·L−1), the fresh weight of Chinese cabbage seedlings was significantly decreased, whereas their root:shoot ratio was increased, indicating that BDE-47 inhibited the growth of the plant, especially the overground parts. The water content, chlorophyll content, and protein content of Chinese cabbage leaves also markedly decreased with the increase of the BDE-47 concentration. In addition, BDE-47 weakened the photosynthetic capacity of the leaves, which was supported by the decreased photosynthetic parameters [net photosynthetic rate (P n) and stomatal conductance (g S)]. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves were enhanced after exposure to BDE-47, the increased malondialdehyde (MDA) content attested to the existence of membrane lipid peroxidation. The increased plasma membrane permeability and the decreased chlorophyll fluorescence parameters [the maximum quantum yield of PSII photochemistry at t = 0 (F v/F m), photosystem II (PSII) reaction centers (RCs) per cross section (CS) (RC/CS), absorption energy flux per CS (ABS/CS), trapped energy flux per CS (TR o/CS), electron transport flux per CS (ET o/CS), performance index on the absorption basis (PI abs), and driving force for photosynthesis (DF)] further proved that the plasma membrane and photosynthetic membrane were damaged by BDE-47. Our study demonstrated the phytotoxicities of BDE-47 to Chinese cabbage, which can provide valuable information for understanding the toxicity of BDE-47 on vegetables.

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