转Bt基因作物毒素在土壤中降解特性的研究进展

总结了国内外转Bt基因作物在土壤中降解特性的研究结果,讨论了土壤有机、无机组分与毒素蛋白的关系,阐明了转基因毒素蛋白在土壤中的降解与影响因素,揭示了转Bt基因作物在土壤中降解的生态环境效应,并提出了今后应深入研究的问题和方向.     

Amelioration of a highly degraded tropical alfisol by planting I. Changes in soil physical and chemical properties 1989-91

This paper examines soil amelioration by planting 15 leguminous and graminaceous plant species, including herbaceous annuals, perennials and biennials, and woody perennials and biennials. Disturbed and undisturbed natural regrowth were planted with leguminous species, in some cases with fertilizer applied at planting (400 kg ha⁻¹ of 15:15:15 NPK). The studies were made on two highly degraded sites in southwestern Nigeria which had been subjected to intensive mechanized cropping for a period of 10 years. Changes in soil physical and chemical properties were monitored from 1989 to 1991. Acacia difficilis, Brachiaria lata and Mucuna utilis had the lowest survival rates by the following growing season. Soil fertility and compaction levels differed between sites. Planting had no effect on the latter. The decreases in compaction (i.e. macroporosity) between 0.00 and 0.10 m depth at both sites one month before and five and 17 months after planting were 43, 59 and 61 per cent, respectively were attributed to exclusion of heavy machinery from the sites. Large decreases in fertility occurred at both sites and were attributed to a combination of nutrient extraction and to leaching. Between fallow species, exchangeable Ca, pH and the cation-exchange capacity (CEC) were greater and total acids lower for herbaceous cover compared with woody perennials, and was attributed to a higher Ca demand by the latter. Highest and lowest values of Ca, CEC and pH occurred in plots where plant material was returned to the soil (i.e. by cutting or die-back) and in cropped plots, respectively. Natural regrowth was as effective or better than planted species in improving soil physical and chemical properties. Therefore the use of exotic plant species for ameliorating highly degraded alfisols is unnecessary. Amelioration of highly degraded alfisols may be best effected by allowing natural regrowth to occur while excluding all mechanized traffic from the site.     

Investigations on the Behaviour of Fenpropimorph and its Metabolite Fenpropimorphic Acid in Soils

The fate of fenpropimorph and its metabolite fenpropimorphic acid was investigated in a silty sand soil and in a clayey silt soil. In laboratory and field experiments fenpropimorph disappeared without a lag phase. A few days after application fenpropimorphic acid was detected. Additional laboratory experiments with [¹⁴C]fenpropimorph emphasized the significance of mineralization and the formation of non-extractable residues. The determination of soil/water distribution coefficients of parent compound and metabolite yielded a higher leaching potential for fenpropimorphic acid due to its higher polarity. This was confirmed by performing a laboratory column test under worst-case conditions. Under field conditions, however, fenpropimorphic acid was detected only in the superficial soil layers (0–5 cm) of both investigation sites at very low concentrations.     

施氮量对番茄根际土壤细菌群落及氮转化功能的影响

为探究施氮量对番茄根际土壤细菌群落组成、结构和氮转化功能的影响,以设施番茄根际土壤为研究对象,通过盆栽试验,设置不施氮处理(CK,0 kg·hm^-2)、低氮处理(L,115 kg·hm^-2)、中氮处理(M,225 kg·hm^-2)和高氮处理(H,450 kg·hm^-2),采用高通量测序技术与FAPROTAX(Functional annotation of prokaryotic taxa)功能预测相结合的方法进行研究。结果表明,放线菌门(Actinobacteria)为主要优势细菌门,相对丰度为35.99%～40.06%,与CK处理相比,M处理放线菌门(Actinobacteria)的相对丰度显著提高,而H处理放线菌门的相对丰度显著降低。M处理的根际土壤细菌群落中,有益细菌属Gaiella、Geminicoccus、红杆菌属(Solirubrobacter)、节杆菌属(Arthrobacter)的比例高于其他处理。施氮量变化未对根际土壤细菌群落的α-多样性产生显著影响,但显著改变了氮转化功能类群的...     

青海省同德县草地现状及畜牧业可持续发展策略

在调查同德县草地退化现状的基础上,综合分析了同德县草地退化的原因,指出了同德县畜牧业可持续发展的策略。同德县的草地退化是自然因素和人为因素共同综合作用的结果。人类活动和气候变化是导致同德县草地退化、区域生态环境恶化的两大因素,鼠虫害对它们产生的影响起了促进作用。只有合理利用和保护天然草地,综合治理退化草地,优化畜牧业产业结构,使草地生态系统步入良性循环,才能使同德县的草地畜牧业协调发展。     

Land degradation,stocking rates and conservation policies in the communal rangelands of Botswana and Zimbabwe

Communal rangeland management policies in Botswana and Zimbabwe are based on incorrect technical assumptions about the stability of semiarid rangeland, the nature of rangeland degradation, and the benefits of destocking. Consequently, inappropriate policies, stressing the need to destock and stabilise the rangelands, are pursued. Acknowledgement of the great instability but intrinsic resilience of rangeland would encourage the Governments to more favourably regard the opportunistic stocking strategies of the agro-pastoralists of the Communal Areas. However, degradation of rangelands is occurring, although at varying rates. This justifies the promotion of a ‘tracking strategy’, in which livestock densities are encouraged to follow, more closely that at present, variations in rainfall. The establishment of grazing territories controlled by specific ‘communities’ may be a prerequisite for the promotion of the tracking strategy, and for communal rangeland management and improvement. However, the establishment of such territories must take into account social equity, institutional problems and transaction costs, as well as spatial and temporal variation in rangeland resources.     

深圳填海区植物根际土壤耐盐菌株筛选与鉴定

【目的】耐盐菌在盐渍土壤中分布广泛,研究其分布特征可为下一步盐渍土改良和降低植物盐害工作提供有益参考。【方法】从深圳坝光和宝安填海区灌木根际采集10个土壤样品,利用不同浓度的NaCl培养基分离耐盐菌种,并通过电镜形态观察和基因组DNA扩增测序对其进行鉴定。【结果】从灌木根际土壤中分离出66株根际菌株,其中14株具有强耐盐能力,可在10%～14% NaCl浓度下生长。电镜结果和16S rDNA序列分析表明,深圳坝光和宝安填海区土壤耐盐菌种类丰富且形态差异明显,14株细菌中有13株来自芽孢杆菌属(Bacillus),1株来自溶杆菌属(Lysobacter)。此外,对其中3株耐盐菌的碳源利用能力分析结果表明,3株菌具有不同的碳源利用能力,NY12可利用的碳源种类最多。【结论】首次对灌木根际耐盐菌株进行分离鉴定,共分离出14株强耐盐菌株,其形态和碳源利用能力差异显著。     

植物源活性成分对有机磷农药的降解效果研究

为探索有机磷农药降解的新途径和方法,以大黄、海桐皮、木槿皮、五倍子按9:4:3:2质量份数混合,粉碎并以水浸泡,以GC-MS定量检测法、农残速测法,通过比较试验前后有机磷农药浓度变动,明确其对有机磷农药的降解效果。结果表明,2 min内浸提液对毒死蜱、对硫磷2种有机磷农药降解率分别达到93.6%、92.9%;浸提液17 h内对敌敌畏降解率为66.67%,11 h内对毒死蜱降解率为48.69%。本研究表明,大黄、海桐皮、木槿皮、五倍子浸提液对毒死蜱、对硫磷、敌敌畏等有机磷农药有显著降解效果。