In situ immobilization and phytoextraction techniques have been used for remediation of Pb and Cd polluted soils. Three rates (0.25, 0.5 and 1.0%) of seven immobilizing agents (cement, slag, phosphate rock, bitumen, Fe- and Al-gels, and δ-MnO2) were tested on three soils containing various levels of Pb (48–192.0 ug/g) and Cd (0.75–3.45 ug/g). All immobilizing agents reduced the plant available Pb and Cd as extracted by DTPA (diethylenetriaminepentaacetic acid). The effectiveness of the various agents in immobilizing Pb and Cd followed the descending order: bitumen > cement > slag > Fe-gel > Al-gel > phosphate rock > δ -MnO2. Cement and phosphate rock fixed Pb and Cd mainly in the carbonate form, whereas the slag, bitumen, Fe-gel, Al-gel and δ -MnO2 fixed the metals mainly in the oxide form.
The results of pot experiment proved the high ability of barnyard grass (Echinnochloa stagninum) to accumulate elevated amounts of Pb and Cd (ranging from 291–2421 and 6.1–45.9 ug metal/g dry matter, respectively). These amounts are higher than those reported for hyperaccumulators, particularly for Pb. The amounts of Pb and Cd removed by barnyard grass represent, on average, 46 and 72% of their initial total contents in the soils, respectively. These results proved that, without any other soil treatments, barnyard grass is highly efficient in removing considerable amounts of Pb and Cd from polluted soil within a reasonably short period of time. Therefore, use of barnyard grass for the phytoremediation of Pb and Cd polluted soils is feasible and recommended as an environmentally safe and cheap method. The most significant finding of this study is to name the barnyard grass as an efficient lead accumulator plant. 相似文献
Background and AimsNeotyphodium lolii is a fungal endophyteof perennial ryegrass (Lolium perenne), improving grass fitnessthrough production of bioactive alkaloids. Neotyphodium speciescan also affect growth and physiology of their host grasses(family Poaceae, sub-family Pooideae), but little is known aboutthe mechanisms. This study examined the effect of N. lolii onnet photosynthesis (Pn) and growth rates in ryegrass genotypesdiffering in endophyte concentration in all leaf tissues. Methods Plants from two ryegrass genotypes, Nui D andNui UIV, infected with N. lolii (E+) differing approx. 2-foldin endophyte concentration or uninfected clones thereof (E)were grown in a controlled environment. For each genotype xendophyte treatment, plant growth rates were assessed as tilleringand leaf extension rates, and the light response of Pn, darkrespiration and transpiration measured in leaves of young (3045d old) and old (>90 d old) plants with a single-chamber openinfrared gas-exchange system. Key ResultsNeotyphodium lolii affected CO2-limited ratesof Pn, which were approx. 17 % lower in E+ than E plants(P < 0·05) in the young plants. Apparent photon yieldand dark respiration were unaffected by the endophyte (P >0·05). Neotyphodium lolii also decreased transpiration(P < 0·05), but only in complete darkness. There wereno endophyte effects on Pn in the old plants (P > 0·05).E+ plants grew faster immediately after replanting (P < 0·05),but had approx. 10 % lower growth rates during mid-log growth(P < 0·05) than E plants, but there was noeffect on final plant biomass (P > 0·05). The endophyteeffects on Pn and growth tended to be more pronounced in NuiUIV, despite having a lower endophyte concentration than NuiD. Conclusions Neotyphodium lolii affects CO2 fixation,but not light interception and photochemistry of Pn. The impactof N. lolii on plant growth and photosynthesis is independentof endophyte concentration in the plant, suggesting that theendophyte mycelium is not simply an energy drain to the plant.However, the endophyte effects on Pn and plant growth are stronglydependent on the plant growth phase. 相似文献
Genetic engineering offers the opportunity to generate unique genetic variation that is either absent in the sexually compatible gene pool or has very low heritability. The generation of transgenic plants, coupled with breeding, has led to the production of widely used transgenic cultivars in several major cash crops, such as maize, soybean, cotton and canola. The process for regulatory approval of genetically engineered crops is slow and subject to extensive political interference. The situation in forage grasses and legumes is more complicated.
Scope
Most widely grown forage, turf and bioenergy species (e.g. tall fescue, perennial ryegrass, switchgrass, alfalfa, white clover) are highly self-incompatible and outcrossing. Compared with inbreeding species, they have a high potential to pass their genes to adjacent plants. A major biosafety concern in these species is pollen-mediated transgene flow. Because human consumption is indirect, risk assessment of transgenic forage, turf and bioenergy species has focused on their environmental or ecological impacts. Although significant progress has been made in genetic modification of these species, commercialization of transgenic cultivars is very limited because of the stringent and costly regulatory requirements. To date, the only transgenic forage crop deregulated in the US is ‘Roundup Ready’ (RR) alfalfa. The approval process for RR alfalfa was complicated, involving several rounds of regulation, deregulation and re-regulation. Nevertheless, commercialization of RR alfalfa is an important step forward in regulatory approval of a perennial outcrossing forage crop. As additional transgenic forage, turf and bioenergy crops are generated and tested, different strategies have been developed to meet regulatory requirements. Recent progress in risk assessment and deregulation of transgenic forage and turf species is summarized and discussed. 相似文献
Ground beetle activity and species richness was monitored using pitfall traps in a plot trial system on a farm in northern England where the effects of organic and conventional fertility and crop protection management were separated within different crop types between 2005 and 2008. As well as analyses on species activity the beetles were split into small, medium‐sized and large groups, and into groups of herbivores and specific Collembola feeders. Crop type had significant effects on the activity of the 20 most abundant species and all groups, generally with most in beans and winter barley and least in vegetables and spring barley. Most significant reactions to crop protection and fertility management were in cereals and grass/clover. Activity of small species was highest in conventionally crop‐protected cereals but not in vegetables, with more medium‐sized and herbivorous species in organic plots, but there was little influence of crop protection management on large and Collembola feeding species. However, large species were significantly more active in organically fertilised cereals and grass/clover, but not in vegetables, and there were more Collembola feeders in conventional cereals but not in grass/clover. Small species were more abundant in conventionally fertilised grass/clover but there were more in organic cereals and vegetables. These inconsistent activity reactions to management were also observed with individual species but most preferred organically managed plots. There were few significant crop protection : fertility management interactions. Species richness was also significantly affected by crop type and where management had an influence, more species were found in organically managed plots. Constrained ordination emphasised that ground beetle activity was influenced more by crops than by management. Given the diverse nature of organic crop rotations, crop type should be considered a major influence in any environmental manipulation aimed at increasing ground beetle activity for provision of ecosystem services. 相似文献