Monosomic additions in beet (Beta vulgaris) carrying extra chromosomes of B. procumbens

Summary Alien monosomic additions in beet (Beta vulgaris), each carrying one of the nine chromosomes of B. procumbens, were grown in vivo and in vitro to study the effect of the alien chromosomes on plant development. All additional chromosomes caused a reduction of the growth rate in vivo, which, in one case was so strong that some of the plants died as seedlings. In general, the morphological plant characteristics were not very useful to distinguish the addition types; this could have been the results of the wide variation in the recipient parent. However, some developmental characteristics proved to be highly chromosome-specific; for plants in vivo this was annuality, in combination with early or late flowering. If grown in vitro, chromosome specificity was observed for growth type (rosette or elongated stem), occurrence and rate of vitrification, occurrence and morphology of wound callus, formation of additional meristems on the midribs of leaves, formation of roots and a specific reaction to benzylaminopurine (BAP) the medium. Two chromosome types of B. procumbens caused resistance to the beet cyst nematode.     

Response and correlation of above- and below-ground functional traits of Leymus chinensis to nitrogen and phosphorus additions

AimsLeymus chinensis is a constructive and dominant species in typical steppe of northern China. The structure and functions of L. chinensis grassland ecosystem has been degenerated seriously due to long-term overgrazing in recent decades. As an effective measure to restore the degraded grasslands, the effects of nutrient addition on plant growth and ecosystem structure and functioning have been paid more attention in manipulation experimental research. The effects of nutrient addition, especially P addition on the above- and below-ground functional traits of L. chinensis have rarely been studied; particularly the underpinning mechanisms remain unclear. Our objective is to examine the responses and adaptive mechanisms of L. chinensis to different levels of N and P additions. MethodsWe conducted a culture experiment in the greenhouse, with three levels of N (50, 100 and 250 mg N·kg^-1) and P (5, 10 and 25 mg P·kg^-1) addition treatments. The above- and below-ground biomass, leaf traits (e.g., specific leaf area, leaf N and P contents) and root traits (e.g., specific root length, root N and P contents) of L. chinensis were determined in this study.Important findings Our results showed that: 1) the aboveground biomass and total biomass of L. chinensis were mostly affected by N addition, while the belowground biomass was mainly affected by P addition. N addition greatly enhanced the aboveground biomass of L. chinensis, while P addition reduced the belowground biomass at the moderate and high N levels. The root-shoot ratio of L. chinensis was influenced by both N and P additions, and root-shoot ratio decreased with increasing N and P levels. N and P additions promoted more biomass and N and P allocations to aboveground and leaf biomass. 2) Leymus chinensis showed different responses and adaptive mechanisms to P addition at low and high N levels. At low N level, L. chinensis exhibited high photosynthetic rate and specific root length (SRL) to improve photosynthetic capacity and root N acquisition, which promoted aboveground biomass. High root P content was favorable for belowground biomass. At high N level, P addition did not significantly affect plant growth of L. chinensis, even reduced its belowground biomass. Leymus chinensis showed high specific leaf area (SLA) and SRL to improve light interception and N acquisition in order to maintain stable aboveground biomass. 3) P addition greatly impacted below-ground than above-ground functional traits. SLA exhibited a weakly positive correlation with SRL, indicating L. chinensis exhibited relatively independence of resource acquirement and utilization between leaf and root functional traits.     

Transmission of alien tomato chromosomes from BC1 to BC2 progenies derived from backcrossing potato (+) tomato fusion hybrids to potato: the selection of single additions for seven different tomato chromosomes

 By backcrossing three BC₁ genotypes of potato (+) tomato fusion hybrids to different tetraploid potato pollinators, BC₂ populations were produced. A combined total of 97 BC₂ plants from three BC₂ populations were analysed with chromosome-specific probes through restriction fragment length polymorphism (RFLP) for the presence of alien tomato chromosomes. The number of different alien tomato chromosomes transmitted through the female BC₁ parent ranged from 0 to 6, and the average number of different alien chromosomes transmitted per BC₂ plant varied between 1.7 and 3.4 in the different populations. This variation corresponded to the chromosome constitution of the individual BC₁ parents: parent 6739, which possessed 11 different alien chromosomes in a single condition, gave rise to progeny with a lower average number of alien chromosomes per plant than the BC₁ parent 2003 that possessed 2 of the 12 alien chromosomes in a disomic condition. In the latter case, the higher transmission rate was attributed to the more regular distribution of the two alien chromosomes in the disomic condition because of regular bivalent formation during meiosis as revealed by genomic in situ hybridisation (GISH) and fluorescent in situ hybridisation (FISH). The transmission frequencies of individual alien chromosomes were subjected to statistical analysis to test whether the maternal genotypes had an effect on alien-chromosome transmission. Among the BC₂ plants, a total of 27 single additions were detected for as many as seven different chromosomes (1, 2, 4, 6, 8, 10 and 12) out of the 12 possible types. Received: 4 March 1997 / Accepted: 28 August 1997     

Visualization of Secale cereale DNA in wheat germ plasm by fluorescent in situ hybridization

Homozygous wheat/rye (1BL/1RS or 1AS/ 1RL) translocation lines have significantly contributed to wheat production, and several other wheat/rye translocation lines show a potential promise against biotic and abiotic stresses. Detecting the presence of rye at the chromosome level is feasible by C-banding and isozyme protocols, but the diagnostic strength of genomic in situ hybridization for eventually analyzing smaller DNA introgressions has greater significance. As a first step we have applied the genomic in situ hybridization technique to detect rye chromosomes in a wheat background using germ plasm of agricultural significance. By this method rye contributions to the translocations 1BL/1RS, 1AL/1RS, 5AS/5RL and 6BS/6RL could be identified. Differential labelling has further enabled the detection of rye and Thinopyrum bessarabicum chromosomes in a trigeneric hybrid of Triticum aestivum/Th. bessarabicum//Secale cereale.     

Mineralization of carbon and nitrogen in acid forest soil treated with fast and slow-release nutrients

The effects of slow (apatite, biotite) and fast-release nutrients (P, K, Mg) on C and N mineralization in acid forest soil were studied. These nutrients were applied alone or together with urea or urea and limestone. The production of CO₂ in the soil samples taken one and three growing seasons after the application was lower in the soils treated with the fast-release nutrients than in the untreated soils. Similar reduction of microbial activity was not seen after the apatite and apatite+biotite treatments. In the first growing season, urea and urea+limestone enhanced CO₂ production, but after three growing seasons, the opposite was true. Apatite and apatite+biotite added together with urea did not compensate for the decreasing effect of urea on the CO₂ production. The addition of fast-release salts increased somewhat the concentration of NH _inf4 ^sup+ in the soil and more NH₄ ⁺ accumulated during laboratory incubation in the soil samples taken one growing season after the application. The urea addition immediately increased the concentrations of NH₄ ⁺ and of NO₃ ⁻ in the soil, but, three growing seasons after application, urea had only a slight increasing effect on mineral N content of the soil. Slow-release nutrients seem to have a more favourable effect than fast-release salts on nutrient turnover in acid forest soil.     

羊草的地上-地下功能性状对氮磷施肥梯度的响应及关联

羊草(Leymus chinensis)是我国北方典型草原群落的主要建群种和优势种, 由于长期的过度放牧, 羊草草原生态系统的结构和功能严重退化。养分添加作为恢复草地生态系统的一种管理措施, 其应用目前还处于实验性研究阶段。关于羊草的地上-地下功能性状对养分添加, 尤其是P添加的响应研究较少, 相关机制尚不十分清楚。为此, 该文以羊草为研究对象, 通过温室栽培进行N (50, 100, 250 mg N·kg^-1)和P (5, 10, 25 mg P·kg^-1)各3个水平的养分添加实验, 研究羊草的地上-地下功能性状对N、P添加的响应及适应机制。主要研究结果表明: 1)羊草的地上生物量和总生物量主要受N添加的影响, N添加显著提高了羊草的地上生物量, 而地下生物量主要受P添加的影响, 尤其在中N和高N水平, P添加显著降低了羊草的地下生物量。羊草的根冠比受N、P添加的共同影响, 随着N、P添加梯度加大, 根冠比显著降低, N、P添加促进了羊草生物量向地上部分的分配和N、P向叶片的分配。2)在低N和高N水平, 羊草对P添加的响应与适应机制不同。低N水平, 羊草主要通过增加光合速率和比根长(SRL), 提高光合能力和根系对N的获取能力促进地上部分的生长, 而根系对P的吸收有利于地下部分的生长; 在高N水平, P添加对羊草的个体生长无明显促进作用, 甚至地下生物量明显受到P素抑制, 羊草主要通过保持较高的比叶面积(SLA)和SRL, 提高对光资源的截获能力和根系对N的获取和吸收能力, 维持地上部分的生长。3)相对于地上性状, P添加对羊草的地下性状影响更大, 羊草的SLA与SRL呈较弱的正相关关系, 表明叶片与根系在资源获取和利用方面具有相对独立性。     

外源性氮磷添加及林分密度对大叶相思林土壤酶活性的影响

研究了林分密度和外源性氮(N)磷(P)添加及二者的交互作用对土壤酶活性的影响,可以为当前不同密度的亚热带林在氮沉降和施磷肥条件下,影响我国亚热带人工林土壤养分转化的酶学机制提供理论依据。以大叶相思(Acacia auriculiformis)人工林为试验材料,选择氯化铵(NH_4Cl)和二水合磷酸二氢钠(NaH_2PO_4·2H_2O)作为N肥和P肥,氮磷添加设置4个处理,即对照、施N、施P和施N+P;种植密度设置低密度(1667株/hm~2)、中密度(2500株/hm~2)、较高密度(4444株/hm~2)和高密度(10000株/hm~2)4个水平。在4种密度的大叶相思人工林下各设置一个样地(即4个样地),每个样地内5个样方,每个样方内设置4种处理,合计共16个处理,5个重复,80个小区,测定土壤脲酶、磷酸酶和过氧化氢酶活性,分析林分密度和NP添加对大叶相思林地土壤酶活性的影响。研究结果表明:N添加对各林分密度下的土壤脲酶和过氧化氢酶活性均有抑制作用,P添加显著提高了过氧化氢酶活性和高密度林分大叶相思林地的土壤脲酶活性,却降低了低密度林分的土壤脲酶活性;土壤磷酸酶活性在P和N+P添加两种处理下显著小于对照和施N处理;土壤脲酶、磷酸酶以及对照和P添加处理下的过氧化氢酶活性均随着林分密度的升高呈现上升趋势,而土壤过氧化氢酶活性在N和N+P添加后随着林分密度的减小而升高。林分密度和外源性NP添加的交互作用对三种土壤酶的活性均有显著影响。     

氮添加对杉木林土壤有机碳矿化速率及酶动力学参数温度敏感性的影响

为探讨氮添加对亚热带森林土壤有机碳矿化速率(Cmin)及酶动力学参数温度敏感性(Q10)的影响,选择亚热带杉木林土壤为研究对象,采用野外长期氮添加与室内控温培养试验,分析土壤Cmin及β~(-1),4-葡萄糖苷酶(βG)动力学参数温度敏感性。野外试验设置对照(N0)、低氮(N1:50 kg N hm~(-2)a~(-1))、高氮(N2:100 kg N hm~(-2)a~(-1)) 3种处理,每种处理3次重复,室内培养设置10—40℃。结果表明:(1)氮添加增加土壤Cmin,为N2N1N0,但其Q10(Cmin)差异不显著。(2)氮添加增加βG的潜在最大反应速率(Vmax)和催化效率(Vmax/Km),且Vmax和Vmax/Km均为N2N1N0,而氮添加对半饱和常数(Km)影响不显著。Q10(Vmax)和Q10(Km)大小为N2N1N0且差异显著,但是Q10(Vmax/Km)无显著差异。(3)相关分析表明,30℃培养温度下,Cmin和全磷(TP)、硝态氮(NO-3-N)、有效磷(a P)、Vmax正相关; Vmax和TP、NO-3-N正相关,和p H负相关; Km和全氮(TN)负相关; Vmax/Km和p H负相关,和TP正相关。30—40℃培养温度下,Q10(Vmax)和p H负相关,Q10(Vmax/Km)和TN负相关。研究可为氮沉降背景下土壤碳素循环的生物化学过程对增温响应的模型提供重要参数。     

氮磷添加对杉木根叶分解残余物微生物群落结构及酶活性的影响

为揭示根、叶分解残余物对生态系统养分循环相关过程的影响,研究了分解第3年杉木根残余物（凋_R）和叶残余物（凋_L）中的微生物群落结构（环丙基脂肪酸/前体结构,Cy/pre;单不饱和脂肪酸/饱和脂肪酸,Mono/sat;真菌/细菌,F/B;革兰氏阳性菌/革兰氏阴性菌,G⁺/G^-）、酶活性（β-葡萄糖苷酶,βG;β-N-乙酰氨基葡糖苷酶,NAG;酸性磷酸酶,AP）、化学元素含量及计量比对氮磷添加的响应。结果表明：（1）与凋_R相比,凋_L中的Cy/pre、F/B、G⁺/G^-低,Mono/sat高。氮磷添加对分解残余物微生物群落结构影响不显著。（2）与凋_R相比,凋_L中的βG和NAG活性高、βG/AP大。氮磷添加抑制了AP活性,提高了βG/NAG及βG/AP。且氮磷添加对凋_R的AP活性抑制作用更强,对凋_L的βG/NAG提升幅度更大。（3）分解残余物中的Mono/sat、G+/G、F/B分别与锰含量、磷/钙、氮含量正相关;AP、βG/NAG分别与氮/磷、磷/铁正相关;βG/AP、NAG、βG分别与氮/锰、磷/镁、氮/钙负相关。表明根、叶分解残余物仍可对生态系统养分循环相关过程产生不同影响,考虑分解残余物类型可提高全球变化背景下生态系统养分循环过程预报精度。     

The [2+1] Cycloaddition of Singlet Oxycarbonylnitrenes to C60

Semiempirical and density functional calculations have been carried out to discuss the origin of the closed [5,6]-aza-bridged adduct obtained as a minor product in the reaction of singlet nitrenes with C₆₀. The results indicated that the most likely source is the direct addition of singlet nitrenes to a [5,6]-bond of C₆₀, in contradiction to the common belief that the [5,6]-bonds are not attacked in cycloaddition reactions to C₆₀.Electronic Supplementary Material available.