Study On Genotypic Variation Of Arsenic Uptake And Its Mechanisms By Upland Rice

As it is hamful to human health and ecological safety, farmland arsenic(As) pollution is one of the important environmental problems in the rice-growing area,. In this study, with HPLC-ICP-MS, ultraviolet spectrophotometer and photosynthetic apparatus, pot experiments were used to study As absorption and translocation in 93 different genotypic upland rice cultivars under the condition of different As element concentration(58.9 mg?kg-1 and 58.9 mg?kg-1),and sort out high absorption gene of upland rice and low absorption gene of upland rice according to their tolerance to arsenic and characteristics of As absorption, accumulation and transport by their overground parts;,and furthermore, explore the differentiation of As absorption, accumulation and distribution and its physiological responses under the stress of arsenic from the angle of growth status(plant height, root length, tiller number and grain weight, weight of aboveground), As weight and distribution in different organs(root, stalk, leaf sheath, leaf, rice husk and rice), iron plaque on root surface and antioxidant enzyme system(POD, CAT, APX, GR),through comparing high(3 varieties) and low(4 varieties) arsenic absorption genotypes of Upland Rice in soil with different arsenic concentration(20.9 mg?kg-1, 58.9 mg?kg-1 and 82.6 mg?kg-1). The study leads to the following results:1. Under the condition of this study, out of the 93 upland rice cultivars V2, V3,V4, V7, V10, V15, V16, V22, V32, V35, V36, V37, V40, V43, V45, V50, V51, V59, V62, V66, V67, V71, V72, V76, V78, V83, V84, V87 and V88 were all normal in growth with no obvious symptoms of arsenic toxicity,but they were significantly different in height, biomass and spike weight. The rest upland rice cultivars sufferred different levels of arsenic toxicity. On this basis,we obtained V2, V16 and V78 which were high arsenic absorption genotypes and and V22, V40, V50 and V62 which were low arsenic absorption genotypes;2. Under the condition of this study, As element content in root, straw, leaf sheath, leaf blade, husk and brown rice of high As absorption genotypes upland rice(V2, V16 and V78) was obviously different from that of high As absorption genotypes(V22, V40, V50 and V62); With the As element concentration in soil increasing, the As content in different organs rose., and ccumulated the most in root, accounting for 60% to 80%, and the least in brown rice(0.10% to 0.25%). As element content in different organs showed characteristicsas follows: root>straw>leaf sheath>leaf>rice husk>brown rice.3. When As element concentration in soil was 20.9 mg?kg-1, As element content in root, straw, leaf sheath of high As absorption genotypes upland rice and was obviouly different from that of low As absorption genotypes, while there was no significant difference in leaf blade, rice husk and brown rice. However, when As element concentration in soil was 58.9 mg?kg-1 and 82.6 mg?kg-1, As element contents in different organs were significantly different between high and low As absorption genotypes.4. With As element concentration in soil increasing,, weight of iron plaque on root surface decreased, and was much lower in high As absorption genotypes upland rice than in low As absorption genotypes; Most As was accumulated in the roots(about 65% to 85%), while a small amount was absorbed iron plaque on root surface(about 15% to 35%). As element contained in iron plaque on root surface of low As absorption genotgype upland rice is higher than high As absorption genotgype.5. Under the condition of this study, plant height, root length, tiller number, aboveground biomass and yield per plant of all the genes of upland rice were reduced, with that of low As absorption genotypes upland rice higher than high As absorption genotypes, and meanwhile the difference among varieties was quite significant.6. Under the condition of this study, the activity of antioxidant enzyme system(POD, CAT, APX and GR) was increased in leave blades of all genotypes upland rice, with high As absorption genotype much more obvious than low As absorption genotype, which made the high as absorption genotypes upland rice more resistive to as.