Study On Screening For Rice Masterials With High Cadmium Accumulation And Its Accumulation Characteristics

Cd is viewed as one of the most toxic pollutants. Phytoremediation is the main means of the recovery of heavy metal soil-pollution currently. But due to ultra-accumulated plants are mostly with slow growth, and small aboveground part, and strong regional features, and research of the pest control and breeding potential is not sufficient, which makes it difficult to make large scale application and promotion. Therefore, it is with significant meaning for the possibility of recovering the Cd polluted farmland soil to select some types of crops, which are adapted with the local climate and machinery cultivation and high accumulation ability. The research adapts field experiments, house plants and root-bag experiments to make difference evaluation of the Cd absorption and accumulation abilities of56pieces of rice parent materials, with the aim to select high Cd accumulation types systematically research their features of absorption and resistance. The main results of the research are as follows:（1） By field tests, it mainly researches the different Cd absorption and accumulation of variety types of rice. It shows that during stooling stage and booting stage, the biomass variations is104.00～231.39g·m-2（CV=19.33%） and462.24～1061.81g·m-2（CV=18.85%） for the56pieces of rice parent materials; while the accumulation variations is0～1.28mg·m-2（CV=50.21%） and1.03～4.40m g·m-2（CV=28.62%）,and the enrichment coefficient variation is0.00～3.33（CV=44.04%） and0.66～2.40（CV=23.58%）, which proves that it is absolutely possible to select types with strong Cd absorption and accumulation capability from the current types.（2） Adapt field plot experiments to analysis the differences of biomass, Cd content, Cd accumulation, and enrichment coefficient and removal factor of different types of rice to select high accumulation types. Based on the Cd accumulation, biomass and enrichment coefficient, the rice could be divided into3types:high Cd accumulation types, low Cd accumulation types and intermediate types, so that confirm the high accumulation type is GR Lu17/548//lu17₉（R3）、Wujin4B（R12）、GR Lu17/IRBN95-199₁（R13）、GR Lu17/548//lu177（R21）、Lu17-T2171（R30）、GR lu17/548//Lu173（R41）、GR Lu 17/IRBN92-332//527₈（R49）.In stooling and booting stage, the average Cd content of high accumulation ones is27.24%and51.74%higher than low accumulation ones; and for average Cd accumulation, it is49.7%and35.35%higher, and the average enrichment coefficient is1.94times and1.52times higher, and for average removal factor, it is1.92times and1.54times higher.（3）Two Cd high-accumulation materialls （Lu17-T2171and Wujin4B） were screened earlier,with common variety Luhui17as contrast. A pot culture experiment was carried out in a net room on the farm of Sichuan Agricultural University, Sichuan province, China in2010. As the concentration of Cd increases, the biomass of Cd high-accumulation materials was also on an increase. Biomass of Lu17-T2171increases by33.96%and19.51%respectively at tillering stage and flowering stage with Cd50, compared with CdO; while that Wujin4B increases by54.71%and15.22%respectively. High-accumulation materials with stronger absorptive capacity to Cd at tillering stage. Under condition of Cd50, Cd contents in shoot and root of Lu17-T2171reach87.24mg·kg-1and400.59mg·kg-1respectively, which are2.38and2.86times higher than Luhui17, while those of Wujin4B reach102.26mg·kg-1and384.77mg·kg-1respectively,72.79and2.86times higher than Luhui17. Enrichment factor of both rice materials decrease as Cd concentration falls, moreover, the high-accumulation materials are apparently higher than common materials. High-accumulation materials with stronger ability to accumulate cadmium at flowering stage. Under condition of Cd50, Cd accumulations in shoot and root of Lu17-T2171reach1847.20μg-pot-1892.06μg·pot-1respectively,2.91and2.74times higher than Luhuil7, while those of Wujin4B reach1895.37μg·pot-1、783.42μg·pot-1respectively,2.98and2.41times higher than Luhui17. Moreover, the migration rate of high-accumulation materials at flowering stage is obviously higher than that of common materials.（4）Two Cd high-accumulation materialls （Lu17-T2171and Wujin4B） were screened earlier,with common variety Luhui17as contrast. A pot culture experiment was carried out in a net room on the farm of Sichuan Agricultural University, Sichuan province, China in2010. Purification rate in plant and shoot of high-accumulation materials is apparently higher than that in common materials. Under condition of Cd50, purification rates in plant and shoot of Lu17-T2171reach5.07%and3.42%at flowering stage,2.86and2.90times higher than Luhuil7, while those of Wujin4B reach4.96%and3.51%,2.79and2.98times higher than Luhui17. Cd high-accumulation rice materials indicates high absorptive capacity and accumulation ability to Cd at tillering stage and flowering stage. Thus, it can be taken as potential restoration material for Cd-polluted farmlands.（5） By root-bag experiments, under Cd stress, to research the Cd combined forms of rhizosphere and non-rhizosphere of high Cd accumulation types and changing of DOM. The result shows that the biomass, Cd content and Cd accumulation of high Cd accumulation rice is obviously higher than the common ones, and compared with normal ones, they are with relative strong resistance. For high Cd accumulation crops, the pH and DOM of the soil in rhizophere is higher than soil in non-rhizophere, and its pH in rhizosphere is larger than common ones. Under CK condition, the pH value of Lu17-T2171in seeding stage and Wujin4B rhizophere is0.14and0.04unit higher than Luhui17, while in stooling stage, it is1.12and0.81unit higher. The changing of DOM is similar to pH value. Under CK conditions, the difference of DOM between the two types of rice in seeding and stooling stage is not unified; under Cd100condition, DOM in rhizophere of high accumulation ones is higher than non-rhizophere, while DOM is utilized by microorganism, which is with the trend of descend. All kinds of Cd content of the two types of rice in soil of rhizophere and non-rhizophere are increased as the increasing concentration. Under the same condition, the content of exchange Cd, Fe-Mn oxide-bound Cd and organic Cd in rhizophere is lower than non-rhizophere, while the Cd content of carbonate fraction in rhizophere is higher than non-rhizophere, and the changing of Cd content of sediment is complicated.