Physiological And Ecological Responses Of Maize To Arsenic Pollution

Arsenic can enter the food chain through water-soil-crops,which not only affects crop growth and development,reduces crop yield and quality,but also poses a tremendous threat to human health.In this dissertation,a combination of potted plants and greenhouse tests was used to study the different responses of genotypes' maize to arsenic contamination;this dissertation also explored the effect of arsenic on maize production,quality and physiological and biochemical traits in order to find out the solution of arsenic pollution control.The results were as follows:1.Differenees of genotypes under arsenic stressArsenic stress significantly affected the growth and development of maize of different genotypes.Root length,plant height and dry weight decreased,and the number of the roots increased.Regarding biomass as a standard,sweet maize and sticky maize were of little anti-arsenic ability.There were significant differences in the absorption and accumulation of arsenic in maize of different genotypes.The concentration factor of the whole plant could reach up to 10.61 times and the concentration factor of root could reach up to 16.35 times while transportation coefficient would reach up to 21.13 times among different genotypes. Regarding accumulation and transportation of arsenic as a standard,we found out forage maize,such as SN2,KD8 was better resistant to arsenic than other genotypes.Taking various factors(breeding and environmental governance) into account and choosing principal component analysis,SN2,LX4 and some other varieties were proven to be as anti-arsenic genotypes.2.Effect of arsenic on yield of kernel At low concentrations of arsenic,the growth of maize enhanced and grain yield increased;at high concentrations of arsenic,the growth of maize was affected and yield decreased.At T2,the yield of ZD958,JN218 enjoyed an increase of 4.5%and 3.2%.At T4, the yield of ZD958,JN218 suffered a decrease of 48.85%and 39.13%.There were significant differences between two genotypes.The range of variation of ear length,the number of rows per ear,the number of kernels per row and 1000-kernel weight of JN218 was greater than that of ZD958 because JN218 was more sensitive to arsenic than ZD958.Arsenic had different impact on yield components:little impact on the number of rows per ear,greater impact on the number of kernels per row and weight of 1000 kernels.The decrease of grain yield should be deduced to the reducing of both the number of kemels per ear and weight of 1000 kernels.3.Effect of arsenic on quality in maizeUnder arsenic treatments,the content of grain protein was in a single peak curve.At T2 treatment,the increase of ZD958,JN218 were 4.9%and 2.5%respectively;at T4 treatment, the decrease of ZD958,JN218 were 22.3%and 18%respectively.With the increased concentration of arsenic,the content of grain amino acids was also in a single peak curve.At T2 treatment,the content of grain amino acids was the highest,an increase of 3.4%and 4.7%respectively;at T4 treatment,the content of grain amino acids was the lowest:the content of grain amino acids for two cultivars declined by 21%.The changes between essential amino acids and non-essential amino acids were the same and the ratio remained unchanged,with the highest content of Glu.With the increased concentration of arsenic,in addition to Cys,Met was positively correlated,the other amino acids had a negative correlation.Arsenic affected the formation of starch with the increased concentration of arsenic.At T2 treatment,the content of starch was the highest,an increase of 4.8%and 2.8%respectively; at T4 treatment,the content of starch was the lowest,a decrease of 8%and 10.8%respectively. Under high concentrations of arsenic,the volume of large size starch grains decreased significantly,while the volume of small size starch grains increased.At T4 treatment,the volume of starch grains which were more than 14.9μm decreased by 35.6%in ZD958;the volume of starch grains which were more than 16.4μm decreased by 26.4%in JN218.There was a significant correlation between the concentration of arsenic and pasting.The pasting temperature of T4 treatment was lower than that of CK in ZD958and JN218.The peak viscosity of ZD958 was significantly lower than that of CK.Arsenic stress affected sugar metabolism of grain significantly and reduced the content of total sugar.The content of Glc,Fru and Mal were increased,while the content of Suc were decreased.The turn of total sugar in ZD958 is:T4> CK> T3.At T4 treatment,total sugar content increased by 77.8%;while at T3,decreased by 7%.The turn of total sugar in JN218 was:T3> T4> CK.At T4 treatment,total sugar content increased by 38%,while T3 decreased by 20%.Under arsenic stress,the content of elements of maize grain,such as P,Mn,Fe,K,Ca, Mg,S was in a single peak.The content of As was relevant to that of Se,B;the content of As was negative to that of P.Under arsenic stress,most of mineral elements in grains were in significantly positive correlation.4.Effect of arsenic on the physiological characteristics of maizeArsenic affected seed germination,seedling growth and development significantly. Germination rate of seed,root length and plant height are the negative correlation to arsenic concentration,but the number of root is relevant.Low concentrations of arsenic stimulated the growth of maize seedlings,and high concentrations of arsenic decreased the growth of maize:,the root was black,its elongation was blocked and root weight dropped.Leaf curled, became less green and finally turned yellow.The plant was not able to blossom and fill,even turned out to suffer death.The accumulation and migration of arsenic is closely related to arsenic concentration, growth stages,tissues and organs.In different growth stages,the absorption rate of arsenic: bloom> mature> joint;transition coefficient:maturity> blossom > jointing.The transfer ability of arsenic from the underground to aboveground would promote and strengthen with growth stages.The distribution of arsenic in maturity is uneven in the tissues and organs, followed by:root> stem> leaf> sheath> grain> other(corncobs,bracteal,tassel,etc.);the spatial distribution of arsenic is:underground> lower> central> top.At low concentration,the arsenic concentration between root and stem was similar to the lower stem and significantly higher than upper stems,that is to say,this part has the ability to resist arsenic.But it had limited scope and had negative correlation to the arsenic concentration,and the existence of differences between the species.The change in arsenic valence can occur in the form of maize into the roots.Stems,leaves and seeds have the ability of changing inorganic arsenic into organic arsenic.The most conversion efficiention was grain which was more than 60%,thus greatly reduced the risk of arsenic poisoning.Arsenic stress affected ultra-structure.Cell membrane and mitochondrial membrane system collapsed and chloroplast sparse layer of particle was board,less levels,uneven distribution of a large number of peroxide and black precipitation.Arsenic would mainly be separated from the vacuole and the cell wall to reduce arsenic poisoning.As stress changed two-dimensional infrared spectrum of the fluorescence spectrum5.Selenium would regulate the arsenic stress.Selenium can play an antagonistic action to arsenic poisoning in maize.At the lower concentration,not only the main root length,plant height and chlorophyll content of maize seedlings increased,but also the photosynthetic rate and kernel yield increased and quality improved.Arsenic improved effectively the activity of POD and the content of protein,fat and starch increased.Starch particles were larger,arsenic concentration was significantly lower.At the higher concentration of selenium,it would increase the arsenic toxicity.