玉米/花生混作改善花生铁营养对花生根瘤碳氮代谢及固氮的影响

研究了石灰性土壤上玉米 (Zea mays L.) /花生 (Arachishypogaea L.)混作改善花生铁营养对花生光合速率、光合产物的运输、花生各部位糖类含量、固氮酶活性以及根瘤内碳氮代谢及其有关酶活性的影响。结果表明 ,玉米 /花生混作改善花生铁营养能够明显增强固氮酶活性 ,进而增加了间作花生根瘤氨基酸的含量 ,这主要是由于玉米 /花生混作改善花生铁营养促进了花生光合作用 ,提高光合产物数量 ,增加光合产物由地上部向地下部的运输 ,但是处理间花生根瘤蔗糖和可溶性糖含量变化不大 ,单作花生根瘤还积累较多淀粉 ,说明不是光合产物的供应导致了花生固氮活性的差异。玉米 /花生混作对花生根瘤碳水化合物代谢水平影响较大 ,混作花生根瘤异柠檬酸脱氢酶 (IDH)、苹果酸脱氢酶 (MDH)、琥珀酸脱氢酶活性明显高于单作 ,而磷酸烯醇丙酮酸羧激 (PEPCK)活性低于单作花生 ,表明混作花生根瘤内三羧酸循环代谢水平较高 ,形成类菌体直接吸收利用的能量物质苹果酸和琥珀酸多 ,能够满足类菌体的固氮需求 ,因此 ,玉米 /花生混作改善花生铁营养增强根瘤碳水化合物代谢水平是提高花生固氮作用的重要原因之一     

哈茨木霉发酵液中肽类物质对豇豆根瘤结构和功能的影响

通过树脂吸附、离子交换、薄层层析、高效液相色谱系统等分离、纯化方法,从哈茨木霉(Trichoderm aharzianum)T2-16菌株发酵液中分离得到一种对豆科作物生长具促进作用的物质,通过质谱等方法鉴定为肽类物质。为探明该活性物质对豆科作物的促生机制,用该活性物质对豇豆种子浸种处理后,进行盆栽实验,通过对盆栽实验中根瘤结构与固氮活性变化的研究,结果显示,该活性物质可增加根瘤侵染组织的面积和根瘤细胞中类菌体的数量,降低根瘤细胞液泡化程度,促进根瘤中公共细胞周膜较多形成,加快类菌体的发育成熟,提高根瘤豆血红蛋白的含量,从而提高根瘤的固氮活性。     

银合欢根瘤细胞的光学显微镜和电子显微镜研究

银合欢接种根瘤菌形成根瘤后,应用光镜和电镜技术观察。银合欢根瘤由分生组织细胞、皮层组织细胞、维管束系统和侵染细胞区域四个不同部分组成。根瘤菌借助于侵染线侵染细胞,释放进入宿主细胞质中,转变成固氮类菌体。最初每个包被膜内只含单独的类菌体,随后较老的侵染细胞中,每个包被膜内含有一个以上的类菌体。因此,成熟根瘤的侵染细胞可见有2~5个类菌体群集包被膜里,并且明显地累积PHB物质,显示电子染色透明颗粒。本文还讨论了上述变化的意义与银合欢根瘤细胞结构和功能的关系。     

基因工程

891394;苜蓿豆血红蛋白cDNA的分子克隆豆血红蛋白是一种与动物肌红蛋白相似的蛋白,是共生固氮根瘤的蛋白。豆血红蛋白结合氧类菌体进行氧分压的调节,对苜蓿根瘤豆血红蛋白的组分,性质及其mRNA和合成的转译水平调节等进行了研究     

超结瘤大豆根瘤的亚显微结构

电镜观察表明,超结瘤大豆未受侵染的宿主细胞中有一明显增大的细胞核。幼年类菌体为椭圆形,里面有个拟核区,正常类菌体有完善的周膜和ＰＨＢ颗粒,受侵染的寄主细胞中出现类似无效根瘤的异常现象;少数类菌体退化或溶解,还有空周膜及裸露的类菌体,这可能是超结瘤大豆固氮活性较低的原因。     

超结瘤大豆根瘤的亚显微结构

电镜观察表明,超结瘤大豆未受侵染的宿主细胞中有一明显增大的细胞核。幼年美菌体为椭圆形,里面有个拟核区,正常类菌体有完整的周膜和PHB颗粒。受侵染的寄主细胞中出现类似无效根瘤的异常现象：少数类菌体退化或溶解,还有空周膜及裸露的类菌体,这可能是超结瘤大豆固氮活性较低的原因。     

不同禾本科作物与花生混作对花生根系质外体铁的累积和还原力的影响

采用土培盆栽方法模拟玉米／花生、大麦／花生、燕麦／花生、小麦／花生、高粱／花生5种种植方式,研究混作对花生根系质外体铁的累积和还原力的影响．结果表明,当花生与5种分泌植物铁载体能力不同的禾本科作物混作时,花生新叶叶色正常,而单作花生则表现出严重的缺铁黄化症状,混作花生各部位的含铁量明显增加．与麦类作物(大麦、燕麦、小麦)混作的花生其各部位铁含量高于与玉米、高粱混作的花生,说明麦类作物改善花生铁营养的能力强于玉米、高粱,而两个玉米品种之间的能力差异不大。这主要是由于麦类作物分泌植物铁载体能力高于玉米、高粱．在花生生长至第50、60和70d时,混作花生根系质外体铁含量也随着逐渐增加,并始终高于单作花生．同时,混作明显地提高了花生根际土壤有效铁的含量,花生根系还原力也逐步提高．混作花生逐渐提高的还原力和介质中不断供给的易被花生还原吸收的铁。在改善花生的铁营养方面起了重要的作用．     

不同禾本科作物与花生混作对花生根系质外体铁的累积和还原力的影响

采用土培盆栽方法模拟玉米/花生、大麦/花生、燕麦/花生、小麦/花生、高粱/花生5种种植方式,研究混作对花生根系质外体铁的累积和还原力的影响.结果表明,当花生与5种分泌植物铁载体能力不同的禾本科作物混作时,花生新叶叶色正常,而单作花生则表现出严重的缺铁黄化症状,混作花生各部位的含铁量明显增加.与麦类作物(大麦、燕麦、小麦)混作的花生其各部位铁含量高于与玉米、高粱混作的花生,说明麦类作物改善花生铁营养的能力强于玉米、高粱,而两个玉米品种之间的能力差异不大,这主要是由于麦类作物分泌植物铁载体能力高于玉米、高粱.在花生生长至第50、60和70d时,混作花生根系质外体铁含量也随着逐渐增加,并始终高于单作花生.同时,混作明显地提高了花生根际土壤有效铁的含量,花生根系还原力也逐步提高.混作花生逐渐提高的还原力和介质中不断供给的易被花生还原吸收的铁,在改善花生的铁营养方面起了重要的作用.     

肯氏相思根瘤亚显微结构观察

肯氏相思根瘤亚显微结构观察结果表明：刚受侵染的寄主细胞的细胞核和质体膨大,线粒体内嵴消失成为圆球状体,内质网膜松散;幼年类菌体细胞外型较小,呈圆形和椭圆形,细胞质浓密,染色深而均匀;成熟类菌体外型较大,形态多样,细胞内聚-β-羟基丁酸（PHB）累积增多;随着根瘤细胞逐渐发育成熟,在类菌体包被内可允1至数个类菌体;在根瘤衰老细胞中,类菌体包被周膜解离破裂,流出电子透明物质。本文还对周膜扩增的问题进行了讨论。     

不同花生品种根瘤固氮特点及其与产量的关系

花生根系着生根瘤,能够直接利用大气中的氮气作为氮源,在花生氮素供应中占有举足轻重的地位.而有关根瘤高效固氮的机理研究甚少.本研究在盆栽条件下,利用¹⁵N示踪技术,研究了19个花生品种根瘤固氮特点及其与产量的关系.结果表明: 不同品种根瘤数量、鲜质量、内含物质和固氮量等指标品种间存在显著差异.根瘤数量和鲜质量变异幅度分别为每盆170.59～696.15个和0.83～3.74 g,变异系数分别为36.1%和41.1%;豆血红蛋白含量和固氮酶活性变异幅度分别为每盆15.51～23.23 mg和2.75～20.46 μmol C₂H₄·h^-1,变异系数分别为13.1%和57.2%,后者明显高于前者,表明固氮酶活性除受豆血红蛋白含量影响外,同时受到其他因素的影响.根瘤固氮和全氮积累量变异幅度分别为每盆0.71～1.82和2.16～3.72 g,变异系数分别为21.6%和12.9%,前者明显高于后者,表明花生根瘤固氮不足时,其他氮源在一定程度上能自动补偿根瘤留下的匮缺.花生以根瘤固氮为主,供氮比例平均占总氮量的2/5以上,最高可达50%,培育高供氮比例的品种,可作为花生减氮栽培的途径之一.上述指标中,除根瘤数量外,其余指标间以及这些指标与产量均呈极显著正相关,表明根瘤固氮生理指标与根瘤供氮能力及最终产量密切相关,提高这些指标有助于同时实现高产和化肥减施.     

Effect of peanut mixed cropping with gramineous species on micronutrient concentrations and iron chlorosis of peanut plants grown in a calcareous soil

To gain a better understanding of the mechanisms of improvement of iron nutrition of peanut (Arachis hypogaea L.) intercropped with maize (Zea mays L.) in calcareous soil, both greenhouse and field experiments were conducted to investigate the rhizosphere (phytosiderophores) effects from maize, barley, oats and wheat with different phytosiderophores release rates on iron nutrition and other micronutrients in calcareous soil. Six cropping treatments were examined in a greenhouse experiment: peanut grown separately in monoculture, normal peanut/maize intercropping (two genotypes: Danyu13, Zhongdan12), peanut/barley intercropping, peanut/oats intercropping, and peanut/wheat intercropping. Additionally, we investigated in a field experiment the same five cropping systems as the greenhouse experiment (maize/peanut intercropping not including Zhongdan12). Our results show that the chlorophyll and active Fe concentrations in the young leaves of the peanut in the intercropping system with different gramineous species were much higher than those of the peanut in monoculture. In greenhouse conditions, the Fe concentration in the shoots of peanut plants grown in the intercropping systems of two maize genotypes separately were 1.40–1.44, 1.47–1.64 and 1.15–1.42 times higher respectively than those of peanut plants grown in monocropping at 55, 60 and 70 days. In particular, the Fe concentration in shoots of peanut plants grown in the intercropping systems of barley, oats and wheat were not only higher than those in monocropping but also higher than those in peanut intercropped cropping with maize. In the field, the concentration of Fe in shoot of intercropped peanut plants in rows 1–3 from gramineous species were significantly higher than in monocropping at the flowering stage. Simultaneously with iron nutrition variation in peanut, Zn and Cu concentrations of intercropped grown peanut increased significantly compared to those in monocropping in the greenhouse experiment, and different intercropping treatments generally increased the Zn and Cu content in the shoot of peanut in the field. Systemic mechanisms may be involved in adaptation to nutrient stresses at the whole plant level. The study suggests that a reasonable intercropping system of nutrient efficient species should be considered to prevent or mitigate iron and zinc deficiency of plants in agricultural practice.     

玉米、小麦与花生间作改善花生铁营养机制的探讨

采用土培盆栽方法模拟研究了玉米／花生、小麦／花生间作对花生铁营养状况的影响及其作用机制。结果表明,禾本科作物与花生间作对花生的铁营养状况有显著影响：当花生与玉米或小麦分别间作时,花生新叶叶色正常,而花生单作则表现出严重的缺铁黄化现象,间作花生新叶活性铁、叶绿素含量明显高于单作,两种间作花生各部位铁含量和吸收量明显高于单作,间作明显地促进了铁向花生地上部的转移;在单作花生表现缺铁症状１４ｄ的时间范围内,其根系质外体铁含量仅是间作花生的５２％～８０％;而根系还原力则是单作花生在表现缺铁症状后迅速提高,至缺铁第６ｄ时还原力达到最大值,随后花生根系还原力迅速下降,而间作花生在０～１４ｄ内还原力增加速度缓慢,在１０～１４ｄ中其根系还原力明显地高于单作花生根系还原力。其主要原因可能是禾本科作物玉米、小麦根系分泌物（如：麦根酸类植物铁载体）螯合土壤中难溶性铁并被花生吸收利用。     

Rotation of maize with cowpea improves yield and nutrient use of maize compared to maize monocropping in an alfisol in the northern Guinea Savanna of Ghana

In the northern Guinea Savanna of Ghana (1984–1987) a field experiment was conducted to study the reasons for beneficial effects of rotating maize (Zea mays) and cowpea (Vigna unguiculata) on yield and N and P use of maize. The treatments included two cropping systems, maize monocropping and maize/cowpea rotation, two levels of nitrogen (0 and 80 kg N ha^-1 as urea) and two levels of phosphorus application (0 and 60 kg ha^-1 P as Volta phosphate rock). Yields and nutrient accumulation of maize were larger in rotation than in monocropping, independent of the N and P level. Fertilizer application (N and P) increased yields of maize in both cropping systems to the same extent. Nitrate contents of the soil after cowpea and after maize monoculture were comparable at the beginning of the cropping period. Also, potential nitrogen mineralization was only slightly larger after cowpea in the unfertilized plots. However, soil nitrate of fertilized plots was similar or even higher under monocropping than under crop rotation, especially in deeper soil layers and at the end of the cropping period. This indicates that in addition to the availability of mineral N, its use by the plants was limiting for the productivity of maize. Root length densities of maize were significant lower in monocropped maize than in maize grown in rotation. Soil physical parameters (infiltration, bulk density, aggregate stability and water capacity) showed a significant deterioration compared to a bush fallow plot, but differed only slightly between the cropping systems. Also in a pot experiment maize growth was much better in the soil from the crop rotation than from the monocropping plots, provided P was eliminated as the main growth-limiting factor. Since this effect persisted in spite of N application and optimization of soil physical properties by mixing the soil with polystyrol it is concluded that the results indicate that yield decline in maize monocropping might be due to allelopathic effects.     

Interspecific root interactions and rhizosphere effects on salt ions and nutrient uptake between mixed grown peanut/maize and peanut/barley in original saline-sodic-boron toxic soil

Two glasshouse studies were conducted to investigate the effect of interspecific complementary and competitive root interactions and rhizosphere effects on the concentration and uptake of Na, Cl and B, and N, P, K, Ca, Mg, Fe, Zn and Mn nutrition of mixed cropped peanut with maize (Experiment I), and barley (Experiment II) grown in nutrient-poor saline-sodic and B toxic soil. Mixed cropped plants were grown in either higher density or lower density. The results of the experiment revealed that dry shoot weight decreased in peanut but increased in maize and barley with associated plant species compared to their monoculture. Shoot Na and Cl concentrations of peanut decreased significantly in both experiments, regardless of higher or lower density. The concentrations of Na also decreased in the shoots of mixed cropped maize and barley, but Cl concentrations increased slightly. The concentration of B significantly decreased in mixed cropping in all plant species regardless of higher or lower density. Rhizosphere chemistry was strongly and differentially modified by the roots of peanut, maize and barley, and mixed growing. There were significant correlations between the root-secreted acid phosphatases (S-APase), acid phosphatase in rhizosphere (RS-APase) and rhizosphere P concentration (RS-P) in the both experiments. The Fe-solubilizing activity (Fe-SA) and ferric reducing (FR) capacity of the roots were generally higher in mixed culture relative to their monoculture, which improved Fe, Zn and Mn nutrition of peanut. Further, there were also significant correlations among FR, Fe-SA and RS-Fe concentrations. Peanut facilitated P nutrition of maize and barley, while maize and barley improved K, Fe, Zn and Mn nutrition of peanut grown in nutrient-poor saline-sodic and B toxic soil.     

施氮和间作对土壤团聚体钾素分配及作物钾吸收的影响

基于2个氮水平(低氮和高氮)下连续种植6年的玉米单作、马铃薯单作及玉米马铃薯间作田间定位试验,采用湿筛法对土壤进行团聚体分级,并测定各粒级全钾、交换性钾和非交换性钾含量,研究氮水平和种植模式对土壤团聚体相关钾素分配的影响。结果表明:土壤团聚体以中团聚体(0.25~2 mm)为主,所分配钾素占土壤钾储量60.6%~65.0%。种植模式和施氮量显著影响团聚体非交换性钾含量和储量,但对全钾、交换性钾无显著影响。高氮水平下,间作比单作加权值提高大团聚体(>2 mm)全钾和非交换性钾储量57.6%和73.6%,中团聚体(0.25~2 mm)全钾和非交换性钾储量21.1%和41.5%。间作增加了玉米钾吸收,但降低了马铃薯钾吸收量。除马铃薯单作外,>0.25 mm团聚体的交换性钾、非交换性钾占比与作物钾吸收量呈显著正相关。总之,间作和施氮可提高土壤中较大粒级团聚体非交换性钾和全钾储量,对促进土壤钾素保存和持续供应有积极意义。