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Effects of Sulfur on Cadmium Accumulation, Photosynthesis and Some Other Physiological Characteristics of Pakchoi(Brassica chinensis L.)Under CadmiumStresses
Received:March 25, 2015  
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KeyWord:cadmium;sulfur;pakchoi;cadmium content;photosynthesis;osmotic substances
Author NameAffiliationE-mail
LIANG Tai-shuai College of Life Science, Northwest A&F University, Yangling 712100, China  
LIU Chang-xin College of Life Science, Northwest A&F University, Yangling 712100, China  
KANG Jing-quan College of Life Science, Northwest A&F University, Yangling 712100, China  
JING Zhi-hao College of Science, Northwest A&F University, Yangling 712100, China  
LÜ Jin-yin College of Life Science, Northwest A&F University, Yangling 712100, China Jinyinlu@163.com 
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Abstract:
      Sulfur has played important roles in the plant stress resistance. Here a pot experiment was performed to investigate the effects of exogenous sulfur(50 mg·kg-1) on the growth, Cd uptake and transportation, photosynthetic characteristics and osmosis-regulating substances of pakchoi(Brassica chinensis L.) cultivar Qibaoqing under different Cd concentrations(0, 5, 25, 50, 100 mg·kg-1). Exogenous sulfur significantly promoted the growth of pakchoi under 5 mg·kg-1 and 25 mg·kg-1 Cd, with the plant height increased by 11.14% and 21.16%, shoot dry mass increased by 22.55% and 19.90%, root dry mass increased by 27.83% and 20.29%, chlorophyll content increased by 11.81% and 15.13%, respectively, compared to no sulfur treatment. However, applying sulfur reduced the translocation factor(TF), shoot bioconcentration factor(BCF) of Cd, but increased BCF in roots. Under 25 mg·kg-1 Cd stress, sulfur significantly reduced shoot Cd content by 24.82%, but increased root Cd content by 23.94%, thus yielding a minimum TF of 29.97%. Compared to no sulfur treatment, adding sulfur significantly enhanced the photosynthesis of pakchoi, with the net photosynthetic rate(Pn) increased by 13.15% and 15.22%, stomatal conductance(Gs) increased by 13.81% and 15.42%, respectively, under 5 mg·kg-1 and 25 mg·kg-1 Cd stress. In the treatment with 25 mg·kg-1 Cd, sulfur also significantly increased the soluble protein, soluble sugar, proline and ascorbate content of pakchoi by 20.82%, 23.34%, 26.79% and 25.72%, respectively. These findings indicate that exogenous sulfur of 50 mg·kg-1 could effectively alleviate 25 mg·kg-1 Cd-induced toxicity to pakchoi through inhibiting Cd translocation from root to shoot, and promoting photosynthesis and osmosis-regulating substance contents.