| Sulfur nutrition can affect the growth of rice seedlings and the accumulation of arsenic in rice roots.However,the SO42-species in the growth medium will promote the growth of sulfate reducing bacteria,increase the risk of mercury methylation and cause other heavy metal pollution problems in rice grains.In addition,trivalent arsenic[As(?)]is the main species in flooded arsenic pollution environment for rice growth.Therefore,the study on the effects of organic sulfur on the As(?)toxicity for rice has important theoretical significance and practical value.In this study,4 rice cultivars,namely Tianyou 998,? Youhang 2,Shanyou 63 and Minghui 63,were used as the materials,a hydroponic culture was used to investigate the effect of reduced glutathione(GSH)on the As(?)toxicity for the above 4 rice seedlings stressed by As(?)and a potting soil culture was used to investigate the effect of GSH on their indexes of rice yield stressed by As(?).In hydroponic test,the concentration of different species of arsenic in hydroponic solution,rice roots and rice leaves of 4 rice seedlings was determined by Ion Chromatography and Inductively Coupled Plasma Mass Spectrometry(IC-ICP-MS).In potting soil culture,the concentration of different species of arsenic in rice grains and rice husks of 4 cultivars was also determined by IC-ICP-MS.The effect of GSH on the uptake and communication of arsenic species in rice plants stressed by As(?)was discussed to provide the theory basis for clarifying the detoxification mechanism of organic sulfur nutrition on the As(?)toxicity for rice.The main results were as follows:1.In hydroponic culture,the rice seedlings of Tianyou 998,? Youhang 2,Shanyou 63 and Minghui 63 were the best amended by GSH at its concentration 40.0,40.0,20.0,60.0 mg·L-1,respectively,after the 4 cultivars were stressed by 2.00 mg·L-1 As(?)for 10 d.Under the optimal concentration of GSH,the uptake of nutrients such as K+,NH4+,NO3-and HPO42' by 4 rice seedlings was extremely significantly(p<0.01)promoted,1.49-6.76 times that in As(?)poisoning group;the chlorophyll SPAD value of rice leaves was enhanced(p<0.01),1.09?1.27 times that in As(?)poisoning group;the dry weight of underground part and overground part of rice seedlings except Shanyou 63 was enhanced(p<0.01),1.09?1.47 times that in As(?)poisoning group;the rice height and roots length except Shanyou 63 were enhanced(p<0.01),1.10?1.13 times those in As(?)poisoning group.2.In hydroponic culture,the total arsenic concentrations in the roots of 4 rice seedlings stressed by 2.00 mg·L-1 As(?)were extremely significantly(p<0.01)decreased by GSH.Furthermore,the total arsenic concentrations in the roots of Tianyou 998,? Youhang 2 and Shanyou 63 were all extremely significantly(p<0.01)decreased with the higher GSH concentration and were the lowest at GSH concentration of 100.0 mg·L-1,23.52%,55.90%and 18.60%of those in As(?)poisoning group,respectively.The total arsenic concentrations in the roots of Minghui 63 was increased after decreased and the lowest at GSH concentration of 60.0 mg·L-1,45.08%of those in As(?)poisoning group.The effect of GSH on the total arsenic concentrations in the leaves of 4 rice seedlings stressed by As(?)was similar to that in the roots,the total arsenic concentrations in the leaves of 4 rice seedlings were the lowest at the GSH concentration of 100.0,100.0,100.0,60.0 mg·L-1,55.99%,62.28%,48.35 and 73.74%of those in As(?)poisoning group,respectively.As(?)and arsenate[As(?)]were the predominant arsenic species in hydroponic solution,rice roots and rice leaves of 4 rice seedlings,the concentration of highly toxic As(?)in the roots and leaves of 4 rice seedlings was extremely significantly(p<0.01)decreased by GSH,its variation was similar to that of their total arsenic concentration.The As(?)concentrations in the roots and leaves of 4 rice seedlings were also the lowest at the GSH concentration of 100.0,100.0,100.0,60.0 mg·L-1,the As(?)concentrations in rice roots were 22.91%,45.59%,14.20%and 38.71%of those in As(?)poisoning group and the As(?)concentrations in rice leaves were 36.15%,36.36%,52.33%and 47.71%of those in As(?)poisoning group,respectively.3.In potting soil culture,the setting percentage of 4 unhusked rice,namely Tianyou 998,? Youhang 2,Shanyou 63 and Minghui 63,was extremely significantly(p<0.01)increased,the rice yield and the number of grain per ear of 4 unhusked rice except Tianyou 998 were also extremely significantly(p<0.01)increased,the 1000-grain weight of 4 unhusked rice except Shanyou 63 were significantly(p<0.05)increased.Among 4 cultivars,GSH had the highest promotion for the indexes of ?Youhang 2 rice yield such as the setting percentage,the rice yield,the number of grain per ear and the 1000-grain weight of unhusked rice,1.13,1.78,1.60 and 1.11 times that in As(?)poisoning group.As a whole,the effect of GSH on the indexes of rice yield of 4 cultivars stressed by As(?)was as followers:? Youhang 2>Minghui 63>Shanyou 63>Tianyou 998.4.In potting soil culture,dimethylarsinate[DMA(?)]was the predominant arsenic species in the rice grains of 4 cultivars,As(?)and DMA(?)were the predominant arsenic species in their chaff.The total arsenic concentration in the rice grains of Tianyou 998 stressed by As(?)was significantly(p<0.05)decreased by GSH,the As(?)concentration in the rice grains and husks of 4 cultivars had no significant relevance with GSH(p>0.05).Furthermore,GSH also had no significant effect on the As(?)concentration in the rice grains and husks of 4 cultivars except the rice husk of ? Youhang 2(p>0.05).In a word,GSH significantly promoted the uptake of nutrients such as K+,NH4+,NO3-and HPO42-by 4 rice seedlings,the accumulation of the total arsenic and highly toxic As(?)in their roots and leaves was decreased by GSH,the physiological and biochemical indexes of 4 rice seedlings were significantly amended and the As(?)toxicity on rice seedlings was significantly relieved.Therefore,the indexes of rice yield were significantly increased.However,GSH had no significant effect on the accumulation of inorganic arsenic in rice grains. |
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