蚕豆中三叶草黄脉病毒编码的NIa-Pro蛋白亚细胞定位特征初步研究

三叶草黄脉病毒(Clover yellow vein virus,ClYVV)是马铃薯Y病毒属(Potyvirus)的重要成员。核内涵体a蛋白酶(NuclearInclusionaProtease,NIa-Pro)是一种由Potyvirus病毒编码的具有蛋白水解酶活性的蛋白,在病毒与寄主互作过程中参与多聚蛋白切割等多种功能的行使。选择2018年在江苏发现的ClYVV蚕豆分离物作为研究对象,对其NIa-Pro蛋白基因进行了克隆和序列测定,结果显示其全长729bp,编码1个24.3kD的蛋白。为进一步研究其亚细胞定位特征,构建了融合YFP荧光标签的重组表达载体YFP-NIa-Pro,利用农杆菌浸润法接种本氏烟(Nicotiana benthamiana)。激光共聚焦显微镜观察结果显示,浸润处理后本氏烟叶片表皮细胞的细胞质及细胞核都有较强的荧光信号。取浸润区样品通过Western-blot检测,结果显示YFP-NIa-Pro在本氏烟叶片中正常表达。这些结果初步表明ClYVV编码的NIa-Pro在细胞质和细胞核均有分布。     

The use of 15N natural abundance variation to examine plant and soil organic fractions in pasture under different management practises

 Pasture systems lack the complexity of natural grasslands and have undisturbed soil profiles relative to arable monocultures. With controlled nitrogen (N) fertilizer inputs and measurable outputs (e.g. grazing and leaching), they can be used to investigate ¹⁵N natural abundance variation as a tool for the study of soil-N processes. In the present study, four pastures of different sward composition and N inputs were examined. Plant shoots and a range of soil fractions, categorized by size, were sampled in May prior to any major N additions, and again in July after initial N inputs had of been made. Samples were analyzed for ¹⁵N natural abundance (δ¹⁵N) and total N (εN). In the May sample plant and soil fractions varied in both ¹⁵N and εN between treatments. The 0.5 mm and 0.2 mm soil factions were comparable within treatments, as were the silt and clay fractions. Between May and July changes were apparent in the δ¹⁵N and εN of shoots and some soil fractions within each plot these corresponded to N inputs or sward type. Changes in silt-N especially, were similar to those occurring in the shoots. No comparable changes were seen in the larger fractions. Not all measured variation was explicable in this study. The inadequacies of the approach are highlighted and suggested improvements discussed. Received: 9 February 1998     

三叶草种传匐柄霉的吸水纸培养检验

匐柄霉(Stemphylium botryosurn)和束状匐柄霉(S.sarciniiforme)引起三叶草和多种豆科牧草的叶斑病,并随种子传播,是牧草种子健康检验的重要对象。本研究发现并确定了这两种病原真菌的吸水纸培养特征,即分生孢子梗型和气生菌丝型,其整体形象易于识别,据此可利用吸水纸培养检验法实施种子带菌的快速检验。     

Early assessment of ecological services provided by forage legumes in relay intercropping

In organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services can vary considerably depending on the growing conditions. The aim of this study was to identify early indicators to assess these two ecological services, thereby giving farmers time to adjust the management of both the cover crop and of the following crop.Nine field experiments were conducted over a period of three years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L. Two levels of fertilization were also tested (0 and 100 kg N ha⁻¹). After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Legume and weed biomass, nitrogen content and accumulation were monitored from legume sowing to cover destruction.Our results showed that a minimum threshold of about 2 t ha⁻¹ biomass in the aboveground parts of the cover crop was needed to decrease weed infestation by 90% in early September and to ensure weed control up to December. The increase in nitrogen in the following maize crop was also correlated with the legume biomass in early September. The gain in nitrogen in maize (the following crop) was correlated with legume biomass in early September, with a minimum gain of 60 kg N ha⁻¹ as soon as legume biomass reached more than 2 t ha⁻¹.Legume biomass in early September thus appears to be a good indicator to predict weed control in December as well as the nitrogen released to the following crop. The indicator can be used by farmers as a management tool for both the cover crop and following cash crop. Early estimation of available nitrogen after the destruction of the forage legume can be used to adjust the supply of nitrogen fertilizer to the following crop.     

不同AM菌根菌分泌的磷酸酶对根际土壤有机磷的影响

以三叶草为材料,利用3室隔网培养方法,研究了4种AM菌根菌侵染三叶草后对根际土壤酸性和碱性磷酸酶活性以及菌丝酶活性对土壤有机P的影响。结果表明,接种AM菌根菌 (9周) 对根际土壤酸性和碱性磷酸酶活性均有增强作用,但作用强度主要取决于菌丝在土壤中的生长状况,Glomus属菌根菌在整个菌丝室 (0~6cm) 都影响土壤磷酸酶的活性,其活性在整个菌丝室中都比Gigaspora的高。同一属不同种的根际土壤磷酸酶活性差异不大。AM菌根根际土壤磷酸酶对土壤有机P的降解有很强的促进作用。     

不同生长年限红三叶生产性能与营养价值比较

为了比较不同生长年限红三叶(Trifolium pratense L.)在生产性能和营养价值方面的差异,确定其最佳利用时期,采用随机区组试验设计,以1至5龄红三叶为供试材料,对影响其生产性能的株高、分枝数、再生速度、干草产量等指标以及影响营养价值的粗蛋白、粗脂肪、钙、磷、酸性洗涤纤维等指标进行测定分析,并用灰色系统理论对其进行综合评价。结果表明:4龄红三叶在生产性能和营养价值方面的综合表现最佳,红三叶最佳利用时期为种植后第4年。     

模拟酸雨对三叶草种子萌发及幼苗生理指标的影响

[目的]为酸雨区三叶草作为地被植物管理提供科学依据。[方法]研究pH为2．5、3．0、3．5、4．0、4．5、6．5（清水）不同梯度酸雨胁迫对地被植物三叶草发芽势、发芽率及幼苗蛋白质含量、丙二醛（MDA）含量、脯氨酸含量和过氧化物酶（POD）活性等生理抗性指标的影响。蛋白质含量采用考马斯亮蓝G－250染色法测定,丙二醛含量采用硫代巴比妥酸（TBA）法测定,脯氨酸含量用酸性茚三酮显色法测定,POD活性采用比色法测定。[结果]在不同pH酸雨影响下,三叶草种子的发芽势、发芽率和幼苗的蛋白质含量随着pH的下降呈下降趋势;丙二醛（MDA）、脯氨酸含量和过氧化物酶（POD）活性随着pH的下降呈上升趋势。[结论]pH〈3．5的酸雨胁迫对三叶草种子萌发及幼苗生理指标影响明显。     

套种三叶草对日光温室樱桃番茄生长及根际土壤环境的影响

通过研究套种三叶草对樱桃番茄生长及根际土壤环境的影响,探索生物多样性栽培模式,改变日光温室单一栽培制度。结果表明,随着三叶草生长量的增加,对土壤养分环境的影响逐渐明显,到樱桃番茄收获时,处理土壤的pH、全盐、速效氮、磷、钾质量分数分别下降2.68%、8.73%、10.78%、19.5%和7.54%;处理土壤脲酶和脱氢酶活性在樱桃番茄生育初期就显著增加,在整个生长期内,平均较对照高17.94%和60.62%;相对于对照,套种三叶草的樱桃番茄产量增加14.44%,果实中可滴定酸减少12.83%,亚硝酸盐减少14.38%,糖质量分数增加16.37%,维生素C质量分数增加17.66%;表明日光温室樱桃番茄套种三叶草能够改善根际土壤酶环境减轻根层土壤磷钾肥的富集,提高樱桃番茄养分利用效率,增加产量,是一种可行的增加生物多样性的栽培方式。     

氮磷钾对红花草固氮根瘤菌生长及种植后土壤肥力的影响

为了发展有机水稻,以红花草-有机水稻轮作培肥水田土壤肥力,研究氮、磷、钾对红花草固氮根瘤菌生长及种植后土壤肥力的影响,为红花草的合理种植、培肥地力提供依据.2012～2013 2年稻后茬种植红花草,过冬前分别单独施用不同用量的氮肥、磷肥、钾肥,以不施肥为对照,探讨不同肥料不同用量对红花草产草量、固氮根瘤菌数量、固氮根瘤菌重量的影响及种植后的土壤肥力变化状况.研究结果表明:红花草前期补施氮、磷、钾,氮素对红花草的影响较大,在施氮75 kg/hm2(N 46％)时,产草量最高,固氮根瘤菌数量最多,固氮根瘤菌重量大;种植后土壤全氮变化表现为不同施氮量增幅随肥料用量增加而增加,施磷、施钾各处理增幅随肥料用量增加而先降后升;土壤速效磷变化为施氮、施磷各处理增幅随肥料用量增加而增加,施钾各处理增幅趋势表现不明显;土壤速效钾变化表现为施氮、施磷各处理增幅变化趋势是随肥料用量增加先升后降,在施氮150 kg/hm2(N 46％)、施磷300 kg/hm2(P205 12％)时,土壤速效钾增幅达最大;土壤有机质变化表现为增幅随肥料用量增加而增加.所以,种植红花草,前期适当补施氮、磷、钾,可以提高红花草产草量,有效提高土壤肥力.     

A mixture of grass and clover combines the positive effects of both plant species on selected soil biota

The introduction of N₂-fixing white clover (Trifolium repens) in grassland is a management measure that may contribute to sustainable grassland systems by making them less dependent on inorganic fertilizers. However, little is known about the impact of this measure on soil biota and ecosystem services. We investigated earthworms, nematodes, bacteria and fungi in an experiment in which white clover-only and a mixture of grass and white clover without fertilization were compared with grass-only with and without fertilization.In comparison with grass-only, white clover-only had a lower total root biomass and a lower C/N-ratio in the above- and below-ground plant biomass. These plant characteristics resulted in a lower bacterial biomass, a lower fungal biomass, a higher proportion of bacterivorous nematode dauerlarvae, a lesser proportion of herbivorous nematodes and a greater abundance of earthworms in clover-only.The quantity and quality (C/N-ratio) of the above- and below-ground plant biomass in the mixture of grass and white clover (20–30% clover in the DM) was comparable with grass fertilized with 150 kg N ha⁻¹ of inorganic fertilizer. Differences between these treatments might show specific clover effects in the grass–clover mixture on soil biota other than quantity and C/N-ratio of the litter. However, the only differences were a higher proportion of bacterivorous nematode dauerlarvae and a different nematode community composition in grass–clover.The soil structure in white clover-only showed a higher proportion of angular blocky elements, a lower penetration resistance, a higher number of earthworm burrows, a higher potential N-mineralization and respiration than the soil in grass-only. This suggests that clover stimulates the ecosystem services of water infiltration and supply of nutrients, but is less conducive to soil structure maintenance. The grass–clover mixture differed from grass-only in a higher respiration and from clover-only in a higher percentage of soil crumbs. We suggest that when clover is introduced in grassland to reduce the reliance on inorganic fertilizer, the mixture of grass and clover maintains the positive impact of grass roots on soil structure and increases the supply of nutrients via the soil food web. Thus, a grass–clover mixture combines the agronomic benefits of the two plant types.