植物性脲酶抑制剂对作物营养和土壤特性的影响

采用15N 尿素进行盆栽试验 ,研究了 4种植物材料 (P1、P2 、P3、P4 )作脲酶抑制剂对高粱和水稻营养效应及土壤特性的影响。结果表明 ,4种植物性脲酶抑制剂对水稻和P1对高粱生长、地上部干重有明显的提高作用 ,且植株叶绿素a b值变幅小。植物性脲酶抑制剂 (除P3外 )提高水稻叶片氨基酸含量 1 2 9%～ 2 5 1 %和植株氮素利用率 5 2 %～ 7 7% ,亦促进高粱植株对氮素的利用。 4种植物性脲酶抑制剂提高两种作物氮素表观利用率 4 3 %～ 1 9 2 %和水稻磷、钾吸收量 ,而对高粱磷、钾吸收有降低作用。植物性脲酶抑制剂能提高两种作物的土壤碱解氮含量。淹水条件下植物性脲酶抑制剂持续作用时间相对较短 ,水稻生长 3 6d ,土壤脲酶活性变化不大 ;高粱生长 48d ,土壤脲酶活性降低 1 0 5%～ 1 8 3 %。     

茶多酚对产脲酶菌生长和脲酶分泌的影响

尿素施入土壤后受土壤脲酶作用易导致氨的挥发和氮素损失[1,2].脲酶抑制剂能够抑制脲酶活性,减缓尿素水解,是提高尿素肥效的重要途径之一.因而脲酶抑制剂的寻找和应用倍受关注[3,4].国内外已开发出品种繁多的脲酶抑制剂,但多数脲酶抑制剂还存在应用效果不稳定和对环境污染问题,制约了其应用[5].     

氢醌、双氰胺组合影响稻田甲烷和氧化亚氮排放研究进展

稻田是大气中CH4和N2O的重要来源。大量氮肥的施入不仅影响稻田CH4和N2O排放,且易造成NH3挥发、NO2-和NO3-淋溶及N2O、N2等形式的氮损失。脲酶抑制剂和硝化抑制剂通过缓解尿素水解及抑制硝化反硝化反应减少稻田N2O排放量,但对稻田CH4产生排放的影响报道不一。脲酶抑制剂氢醌(HQ)和硝化抑制剂双氰胺(DCD)是近年来研究较多的组合。本文试图在前人研究的基础上,综述HQ和DCD的基本性质及作用机理,总结HQ/DCD组合在稻田生态系统的应用状况、使用效果及存在问题,并特别讨论了HQ/DCD施用对稻田CH4排放的影响机理,旨在为合理使用脲酶/硝化抑制剂、有效减缓稻田温室气体排放和提高氮肥利用率等方面提供理论依据。     

关于几种土壤脲酶抑制剂的作用条件

近10年来,几种有效的脲酶抑制剂如N-丁基硫代磷酸三胺N-（n-butyl）thiophosphrictriamide（nBPT）、苯基磷酸二胺phenylphosphorodiamidate（PPD）和氢醌hydroquinone（HQ）受到广泛的关注。脲酶抑制剂能够抑制尿素的水解,因而减少了尿素氮的氨挥发损失。然而,脲酶抑制剂的有效性与环境条件（如土壤pH、通气性以及作物残茬有无）有关。目前的研究表明,脲酶抑制剂用在氨易于挥发的土壤上和脲酶抑制剂的作用环境满足时显示了良好的应用前景。因此应用脲酶抑制剂可能对节省尿素肥料施用量,同时确保提高作物产量、减少环境污染提供一种可持续的农业生产技术。本文论述了几种脲酶抑制剂对尿素氮的转化、作物氮吸收和产量等的影响,使对脲酶抑制剂的潜在农用价值、使用条件及其有效用量有所认识。     

杀虫双对土壤脲酶活性特征的影响

通过模拟方法研究杀虫双对土壤脲酶活性特征参数的影响。结果表明 :不同生态区域土壤脲酶特征具有明显差异。杀虫双明显抑制脲酶活性 ,且随浓度增加 ,脲酶活性、酶促反应的Vmax、Vmax/Km、k减小 ,Km 增大 ,除 6号土样的Km 处理外均达到显著或极显著相关 ,揭示出脲酶特征参数可从不同角度表征杀虫双对土壤脲酶活性的影响 ,获得其作用机理为混合型抑制。脲酶活性ED50 值与土壤有机质、全氮和全磷呈现显著或极显著正相关关系 ,表明高有机质含量的土壤可明显减轻杀虫双的污染。     

土壤温度和含水量互作对抑制剂抑制氮素转化效果的影响

为比较生化抑制剂组合对土壤氮素转化的抑制效果,揭示不同土壤温度和含水量互作对尿素水解抑制效应的影响。该文采用室内模拟培养方法,研究土壤含水量(60%和80%田间最大持水量,water holding capacity,WHC)和土壤温度(15、25和35℃)互作对生化抑制组合[N-丁基硫代磷酰三胺(N-(n-butyl)thiophosphoric triamide,NBPT)、N-丙基硫代磷酰三胺(N-(n-propyl)thiophosphoric triamide,NPPT)和2-氯-6(三氯甲基)吡啶(2-chloro-6(trichloromethyl)pyridine,CP)在黄泥田土壤中抑制氮素转化效果的影响。结果表明:土壤温度和含水量对生化抑制组合在黄泥田土壤中抑制尿素水解效应显著,以土壤温度影响更大。随着土壤温度增加,尿素水解转化增强,有效作用时间降低,硝化作用增强,脲酶和硝化抑制效应减弱;随着土壤含水量降低,尿素水解转化缓慢,有效作用时间延长,硝化作用减弱,脲酶和硝化抑制效应增强。不同土壤温度和含水量条件下,NBPT/NPPT或配施CP处理有效抑制黄泥田土壤脲酶活性,延缓尿素水解;CP或配施NBPT/NPPT处理有效抑制NH4+-N向NO_3~--N转化,保持土壤中较高NH_4~+-N含量长时间存在。新型脲酶抑制剂NPPT单独施用及与CP配施的土壤尿素水解抑制效果与NBPT相似。黄泥田土壤中生化抑制组合应用最佳的土壤温度和含水量分别为25℃和60%WHC。总之,针对不同土壤温度和含水量条件,在黄泥田土壤中应采用脲酶抑制剂与硝化抑制剂相结合的施肥方式。     

第四类脲酶抑制剂对土壤脲酶活性和微生物量的影响

[目的]研究第四类脲酶抑制剂对土壤微生物的影响,揭示此类脲酶抑制剂的微生物学效应,为农业生产中施用含Schiff碱配合物型脲酶抑制剂缓控释尿素的安全性评价提供理论依据。[方法]采用室内恒温恒湿培养的方法,测定在不同浓度(按尿素施用量的0.1%,0.5%,1%)新型Schiff碱铜配合物型脲酶抑制剂作用下土壤脲酶活性以及土壤细菌、真菌和放线菌微生物量指标。[结果]①当抑制剂施用浓度为0.1%和0.5%时对土壤脲酶活性影响不显著,当施用浓度为1%时,对土壤脲酶活性抑制效果最好,最大抑制率达40.8%,起到了适度调控的目的;②土壤细菌、真菌和放线菌对尿素水解的敏感程度不同,其中放线菌和真菌比较敏感,尿素水解对其最大抑制率分别为46.4%和89.7%。与此相反,尿素的水解反而会促进细菌生长,最大促进率达83.6%;③第四类脲酶抑制能够促进土壤细菌、放线菌和真菌的生长,其对细菌、放线菌和真菌的最大促进率分别为86.2%,31.9%和83.6%。因此第四类脲酶抑制剂对土壤放线菌生长的促进作用较小,对土壤细菌和真菌生长的促进作用较大。[结论]第四类脲酶抑制剂对土壤脲酶活性有很好地抑制作用且能促进土壤细菌、真菌和放线菌的生长,施用抑制剂浓度为1%时效果最显著,即1%为其最佳用量。     

乙草胺对土壤脲酶动力学特征的影响

采用室内模拟试验方法,以典型棕壤为供试土壤,研究不同浓度乙草胺对土壤脲酶活性和酶动力学参数的影响。结果表明,不同浓度乙草胺能显著抑制土壤脲酶活性,并在培养的第3～6 d达到最大抑制;利用模型 y=c/(1+bx)和y=c(1+ax)/(1+bx) 对不同浓度乙草胺与土壤酶活性的关系进行拟合,证明模型y=c/(1+bx)拟合效果较好,表明乙草胺除草剂对土壤脲酶的抑制作用为完全抑制,而脲酶ED50 为13.12～75.76 mg/kg;乙草胺的施入使土壤脲酶Vmax值降低,Km值则保持不变,属于典型的非竞争性抑制。     

N-丁基硫代磷酰三胺对淹水土壤脲酶动力学特征的影响

研究了淹水状态下脲酶抑制剂N-丁基硫代磷酰三胺(NBPT)对东北4种典型土壤(黑土、白浆土、棕壤、褐土)脲酶动力学参数的影响。结果表明,NBPT对土壤脲酶动力学参数的作用程度受土壤类型、培养时间及其交互作用的显著影响。与对照相比,NBPT使土壤脲酶米氏常数(Km)增加,最大反应速率(Vmax)和Vmax/Km降低,表明NBPT对土壤脲酶的作用机理属于典型的混合型抑制。随培养时间延长,土壤脲酶Km降低,Vmax和Vmax/Km升高,表明NBPT对脲酶的抑制效力逐渐减弱。黑土、白浆土脲酶Km值小于棕壤和褐土,而Vmax则大于棕壤和褐土,表明土壤肥力水平能够影响土壤脲酶的动力学参数。相关分析表明,土壤脲酶Km与粘粒和粉粒含量呈显著正相关关系,与pH值呈显著负相关关系;而Vmax和Vmax/Km的相关性则正好与此相反。     

珠穆朗玛峰北坡土壤脲酶和中性磷酸酶活性初步研究

研究了珠穆朗玛峰北坡地区沿绒布河谷海拔4400～5550m的夏季土壤中水解酶类脲酶、中性磷酸酶活性,并探讨了这两种土壤酶与土壤有机质和海拔高度的相互关系。结果表明:(1)随着海拔升高,土壤脲酶、中性磷酸酶活性呈高低波动变化,在研究区域出现多个峰值,总的趋势是上升的,其最大值分别出现在海拔5500m和5450m处。(2)偏相关分析表明,土壤脲酶活性与有机质含量呈正相关,土壤中性磷酸酶活性与有机质含量呈显著正相关;土壤脲酶活性与海拔的相关性不具显著性意义,中性磷酸酶活性与海拔呈极显著正相关。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.