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Effects of vanadium stress on growth, vanadium accumulation, and translocation in alfalfa
Received:October 09, 2020  
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KeyWord:vanadium;alfalfa;stress response;accumulation
Author NameAffiliationE-mail
WU Zhen-zhong College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
College of Architecture and Environment, Sichuan University, Chengdu 610065, China 
 
YANG Jin-yan College of Architecture and Environment, Sichuan University, Chengdu 610065, China  
ZHANG You-xian College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China phyto_33@126.com 
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Abstract:
      The study aims at providing a theoretical basis for the restoration of vanadium environmental pollution using alfalfa by evaluating its growth response, vanadium accumulation, and translocation characteristics under vanadium stress. An indoor hydroponic experiment was designed with nutrient solution of varying vanadium concentrations(0, 0.1, 0.5, 2.0, 4.0, 10.0 mg·L-1 V), where alfalfa's plant height, root length, chloroplast pigment, photosynthetic gas parameters, degree of leaf membrane lipid peroxidation, cell membrane permeability, biomass, vanadium concentration in each tissue, vanadium translocation factor(TF), vanadium uptake amount in shoots, roots, the whole plants, and the percentages of shoots, roots vanadium uptake amount to total intake quantities under each vanadium concentration were determined. The results revealed that, at low vanadium concentration(0.1 mg·L-1 V), the root length, chloroplast pigments(chlorophyll a, b, and carotenoid) content, leaf net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs), intercellular CO2 concentration(Ci)and biomass were not significantly increased(P>0.05). In contrast, high vanadium concentrations(≥4.0 mg·L-1 V) significantly reduced the plant height, root length, chloroplast pigments, Tr, Gs, Pn, and biomass; meanwhile, the degree of leaf membrane lipid peroxidation and membrane permeability significantly increased(P<0.05). Compared with the control, the root length markedly decreased at ≥0.5 mg·L-1 V. At 2.0 mg·L-1 V, the shoot and total dry matter mass declined markedly(P<0.05). Nevertheless, plant height, chloroplast pigments, photosynthetic gas parameters, degree of leaf membrane lipid peroxidation, and membrane permeability were not conspicuously affected at 0.5 mg·L-1 V and 2.0 mg·L-1 V(P>0.05). Vanadium concentration in control plant tissues was in the order of leaf > root > stem, and the order in vanadium-treated seedlings was root > stem > leaf. The roots were the primary storage site for vanadium in the plant. TF was initially decreased and then increased slightly with increasing vanadium. The maximal vanadium uptake amount of 0.546 4 mg was obtained in plant shoots per pot at 4.0 mg·L-1 V. Although the plant growth was significantly inhibited at ≥4.0 mg·L-1 V, the vanadium uptake of the root, shoot, and the whole plant increased substantially relative to treatments of ≤2.0 mg·L-1 V. In conclusion, the alfalfa plant is relatively resistant to vanadium stress with the potential to remediate vanadium environmental pollution.