Determination of a Critical Nitrogen Dilution Curve for Winter Wheat Crops

A set of N-fertilization field experiments was used to determinethe 'critical nitrogen concentration', i.e, the minimal concentrationof total N in shoots that produced the maximum aerial dry matter,at a given time and field situation. A unique 'critical nitrogendilution curve' was obtained by plotting these concentrationsN_ct (% DM) vs. accumulated shoot biomass DM (t ha^-1). It couldbe described by the equation: N_ct = 5·35DM^-0·442 when shoot biomass was between 1·55 and 12 t ha^-1. Anexcellent fit was obtained between model and data (r² = 0·98,15 d.f.). A very close relationship was found using reducedN instead of total N, because the nitrate concentrations inshoots corresponding to critical points were small. The criticalcurve was rather close to those reported by Greenwood et al.(1990) for C₃ plants. However, this equation did not apply whenshoot biomass was less than 1·55 t ha^-1. In this case,the critical N concentration was independent of shoot biomass:the constant critical value N_ct = 4·4% is suggested forreduced-N. The model was validated in all the experimental situations,in spite of large differences in growth rate, cultivar, soiland climatic conditions; shoot biomass varying from 0·2to 14 t ha^-1. Plant N concentration was found to vary by a factor of fourat a given shoot biomass level. In the heavily fertilized treatments,shoot N concentration could be 60% higher than the criticalconcentration. Most (on average 80%) of the extra N accumulatedwas in the form of reduced N. The proportion of nitrate to totalN in shoot mainly depended on the crop stage of development.It was independent of the nitrogen nutrition level.Copyright1994, 1999 Academic Press Winter wheat, Triticum aestivum, arable crops, plant N concentration, aerial biomass, critical nitrogen, dilution curve, fertilization, reduced N, nitrate     

Determination of Critical Nitrogen Dilution Curve Based on Stem Dry Matter in Rice

Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N) requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (N_c) dilution curve based on stem dry matter (S_DM) and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L.) in east China. Three field experiments with varied N rates (0–360 kg N ha⁻¹) using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. S_DM and stem N concentration (SNC) were determined during vegetative stage for growth analysis. A N_c dilution curve based on S_DM was described by the equation (N_c = 2.17W^−0.27with W being S_DM in t ha⁻¹), when S_DM ranged from 0.88 to 7.94 t ha⁻¹. However, for S_DM < 0.88 t ha⁻¹, the constant critical value N_c = 1.76% S_DM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI) and accumulated N deficit (N_and) of stem ranged from 0.57 to 1.06 and 51.1 to −7.07 kg N ha⁻¹, respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or N_and could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The S_DM based N_c dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China.     

Light Restriction Delays Leaf Senescence in Winter Oilseed Rape (Brassica napus L.)

Oilseed rape (Brassica napus L.) is a crop with a complex aerial architecture that can cause self-shading leading to a vertical light gradient over the foliage. Mutual shading between neighboring plants at a high sowing density also results in an alteration of photosynthetically active radiation (PAR) absorption by lower leaves. The aim of this study was to analyze the impact that light restriction on lower leaves has on shoot architecture, biomass production and allocation, nitrogen (N) fluxes, and progression of sequential senescence. Field-grown plants were collected at the end of the vegetative rest period and grown in hydroponic conditions until pod maturity. A shading treatment corresponding to a 43.4 % reduction of PAR was applied at the early flowering stage. N uptake and fluxes of N allocation and remobilization were determined by supplying K¹⁵NO₃ in the nutrient solution. Photosynthesis and expression of SAG12 and Cab genes (indicators of leaf senescence progression) were also analyzed on different leaf ranks. The results showed that shading enhanced leaf development on the main stem and ramifications to optimize light capture. The expression pattern of the SAG12/Cab molecular indicator suggested a delay in leaf senescence that allowed leaf life span to be extended resulting in a more efficient leaf compound remobilization, with lower N residual contents in fallen leaves under shading. N uptake increased and N remobilization fluxes were enhanced from source organs (leaves and stem) toward sink organs (flowers). Profuse branching and late senescing varieties would be of interest for further selection programs under high sowing densities.     

Developmental Profile of Diacylglycerol Acyltransferase in Maturing Seeds of Oilseed Rape and Safflower and Microspore-Derived Cultures of Oilseed Rape

Diacylglycerol acyltransferase (EC 2.3.1.20) activity was assayed during the maturation of seeds of oilseed rape (Brassica napus L.) and safflower (Carthamus tinctorius L.). Developmental studies were also conducted with microspore-derived embryos of oilseed rape (B. napus L. cv Topas) and an embryogenic microspore-derived cell-suspension culture of winter oilseed rape (B. napus L. cv Jet Neuf). In the maturing seeds, diacylglycerol acyltransferase activity increased to a maximum during rapid accumulation of lipid and declined, thereafter, with seed maturity. In microspore-derived embryos of oilseed rape (cv Topas), high levels of diacylglycerol acyltransferase activity were found throughout the early torpedo to late cotyledonary developmental stages with maximum enzyme specific activity associated with the mid-cotyledonary developmental stage. The cell-suspension culture of winter oilseed rape (cv Jet Neuf) contained 3 to 4% triacylglycerol on a dry weight basis and represented about half of the total lipid. The fatty acid profile of total lipid and triacylglycerol in the cell-suspension culture was similar in samples taken during a 1-year period. The Jet Neuf culture contained diacylglycerol acyltransferase with specific activity similar to that of Topas microspore-derived embryos. Jet Neuf diacylglycerol acyltransferase also displayed an enhanced specificity for erucoyl-CoA over oleoyl-CoA when assayed with 14 [mu]M acyl-coenzyme A in the reaction mixture. The specific activity of diacylglycerol acyltransferase in homogenates prepared from the Jet Neuf culture ranged from 5 to 15 pmol of triacylglycerol min-1 mg-1 of protein when assayed at intervals during a period of 1 year. Thus, the cell-suspension culture may represent an attractive tissue source for purification and characterization of triacyl-glycerol biosynthetic enzymes.     

特早花甘蓝型油菜的开花特征及特早花候选基因鉴定

开花是植物从营养生长进入生殖生长的重要阶段.油菜早花早熟,可有效解决油菜与其他夏季作物的茬口矛盾.挖掘不同的早花油菜资源,研究油菜早花性状形成的分子机理,可促进利用分子技术快速选育早熟油菜的育种进程.本研究以1个新发现的稳定遗传的特早花油菜迎春一号为研究对象,在覆盖全年9个月的时间中设计了15个不同的播种期,调查其开花...     

Biological and Molecular Characterization of a Crucifer Tobamovirus Infecting Oilseed Rape

In China, the tobamovirus that infects oilseed rape has been misdiagnosed as Tobacco mosaic virus (TMV) based on its morphological similarity and serological relatedness. Recently, a tobamovirus has been isolated from oilseed rape in China, which we named Youcai mosaic virus Br (YoMV-Br), according to its biological and molecular characteristics. It had strong infectivity to Cruciferae but less to Solanaceae, Leguminosae, and Cucurbitaceae, and its virion morphology was consistent with that of the tobamoviruses. At high concentrations, it serologically cross reacted with TMV antiserum. The 3′ terminal sequence (2,283 nucleotides) of YoMV-Br was determined, including the 3′ noncoding region, the CP and MP genes, and the C-terminal part of the replicase gene. Between the MP and CP genes, 77 nucleotides overlapped. Compared with homologous regions of 21 recognized species of Tobamovirus, YoMV-Br had a much higher identity to crucifer species than to other tobamoviruses. Phylogenetic analysis demonstrated that YoMV-Br was closely related to the YoMV cluster of tobamoviruses and distantly to TMV, so that they likely belong to different strains of the same species.     

油菜(Brassica napus L)收获指数的变异

本文首次采用田间试验的方法对国内油菜收获指数的变异进行了研究．结果表明不同油菜品种的收获指数存在变异,其变异规律大致是：１）中熟品种的收获指数高于早熟品种及晚熟品种;２）中长角果的品种较长角品种具有更高的收获指数;３）高产的新品种具有较高的收获指数;４）油菜粒壳比,角杆比及千粒重与收获指数呈正相关,杆重与收获指数呈负相关．     

HPLC法分析油菜种子油中维生素E的组成与含量

利用HPLC法分析了50份遗传背景丰富的白菜型油菜、甘蓝型油菜、芥菜型油菜和芸芥种子油中维生素E的组成与含量.研究结果显示,油菜种子油中主要含α-生育酚和γ -生育酚,且a-生育酚、γ-生育酚和维生素E总量均存在明显的基因型差异,甘蓝型油菜种子油中维生素E含量总体水平最高,平均总量较高,为123.11 mg/100g油,维生素E含量最高的Omega,总量为144.73 mg/100g油,α/γ-生育酚比值最高可达0.77.α-生育酚、γ-生育酚和维生素E总量与类胡萝卜素含量均呈现显著负相关,种子油中α-生育酚与含油量呈现显著正相关,α-生育酚、γ -生育酚和维生素E总量与生育期均呈现显著或极显著正相关,α-生育酚和维生素E总量与株高均呈现显著正相关,维生素E总量与千粒重呈显著正相关,而α-生育酚、γ-生育酚和维生素E总量与全株角果数和每角粒数相关不显著.     

Developmental Regulation of a Plasma Membrane Arabinogalactan Protein Epitope in Oilseed Rape Flowers

We have identified and characterized the temporal and spatial regulation of a plasma membrane arabinogalactan protein epitope during development of the aerial parts of oilseed rape using the monoclonal antibody JIM8. The JIM8 epitope is expressed by the first cells of the embryo and by certain cells in the sexual organs of flowers. During embryogenesis, the JIM8 epitope ceases to be expressed by the embryo proper but is still found in the suspensor. During differentiation of the stamens and carpels, expression of the JIM8 epitope progresses from one cell type to another, ultimately specifying the endothecium and sperm cells, the nucellar epidermis, synergid cells, and the egg cell. This complex temporal sequence demonstrates rapid turnover of the JIM8 epitope. There is no direct evidence for any cell-inductive process in plant development. However, if cell-cell interactions exist in plants and participate in flower development, the JIM8 epitope may be a marker for one set of them.     

Nodulation of Oilseed Rape (Brassica napus) by Rhizobia

Nodules were induced on the non-legume oilseed rape, followingenzyme treatment of seedling roots and inoculation with Rhizobiumlegnminosarum, Bradyrhizobtum 32H1 or a mixture of R. lott withBradyrhizobium 32H1 in the presence of PEG. A Nod– strainof R leguminosarum also induced nodules, but a Nod– strainfailed to elicit this response Nodules induced on oilseed rapewere morphologically similar, when examined by light microscopyand cryo-scanning electron microscopy, to those induced on rootsof white clover by R trifolu. Transmission electron microscopyshowed rhizobia within cells of the nodules These observationsare discussed with respect to the extension of Rhizobium symbiosisto non-legumes. Key words: Brassica napus, Bradyrhizobium, Rhizobium, non-legumes, nodulation, transmission electron microscopy, cryo-scanning electron microscopy, acetylene reduction, cell wall degrading enzymes     

Agronomic Performance of Partly Clubroot-resistant Spring Oilseed Turnip Rape Lines

In field experiment studies that tested the effects of three partly resistant cultivars of spring oilseed turnip rape ( Brassica campestris ), multiplication of clubroot was moderate. When initial soil inoculum levels were 47–72% of infected test plants in the bioassay, only 2.1–10% of the plants were infected after harvest. The yield of partly resistant lines was 5–10% higher compared with that of the susceptible cultivar SW Kulta, which on average yielded 1.73 t/ha. The average disease severity index (DSI) after harvest in these trials was 12.7 for the nonresistant cultivar SW Kulta and ranged between 2.2 and 6.2 for the partly resistant lines. The study demonstrated that in fields where the soil infestation level gives a DSI of less than 10, or when less than 20% of the bait plants are infected in the bioassay, it is possible to avoid the risk of severe yield losses from clubroot infections by integrating a partly resistant cultivar into the crop rotation.     

Ovule Development and Determination of Seed Number Per Pod in Oilseed Rape (Brassica napus L.)

Seed number per pod at maturity over the terminal raceme ofsingle plants of oilseed rape is closely correlated to the percentageof ovules with complete embryo sacs (ovule fertility) at floweropening. Approximately one-third of the ovules did not containan embryo sac and sterility, due to the absence of embryo sac,accounted for most of the difference between the numbers ofovules and seeds. Within the terminal raceme, both a decreasedproportion of fertile ovules and a lower number of ovules perovary in apical flowers contributed to the lower number of seedsper pod in the mature apical pods compared to the basal ones.A study of ovule development before flower opening showed thatdifferences in the differentiation of the embryo sacs arosebefore the buds were 40 mm long and probably involved the stagesof meiosis II and/or differentiation of the chalazal megaspore. Key words: Oilseed rape, ovule development, seed number per pod     

Interactions between Root Temperature and Nitrogen Deficiency Influence Preferential Uptake of NH+4 and NO-3 by Oilseed Rape

Oilseed rape (Brassica napus L. cv. Bien venu) plants were grownin a system of flowing solution culture and pre-treated at roottemperatures of 3 ?C or 13 ?C for 7 d with or without N suppliedas 10 mmol m^–3 NH₄NO₃. Subsequently, N was re-suppliedand root temperatures were reversed for 7 d. Shoot temperatureswere common at 20/15 ?C day/night. Net uptake of , and K⁺, leaf area, root length, and transpirationwere measured and compared with control plants having root temperaturesof 3 ?C and 13 ?C throughout. Plants that were continuouslysupplied with N and pre-treated at 3 ?C showed a 50% increasein total uptake of , and measured at 13 ?C over 7 d compared with control plants at 3?C,but uptake of was 28% lower and uptake of was 43% higher than that shown by control plants at 13 ?C. Pre-treatment at 3 ?C did not enhance the subsequentuptake of total N or of K⁺ at 13 ?C relative to the 13 ?C control.Transpiration rates at 3 ?C were on average 70% of those at13 ?C. The concentration of total N in plants was halved after7 d without a supply of N, but total dry matter production wasnot significantly affected. N starvation also increased thetemperature sensitivity of subsequent uptake relative to that of uptake. After N starvation at 13 ?C the uptake of and measured at 13 ?C was 50% higher over 7 d than that measuredunder continuous N supply. In contrast, after N starvation at3 ?C the uptake of at 3 ?C was 70% less, whilst uptake was 50% more than the respective totals absorbed by plants that were continuously supplied withN at 3 ?C. After N starvation the uptake of was generally 40–60% of the daily total N uptake, comparedwith 60–80% in plants continuously supplied with N. Key words: Brassica napus, oilseed rape, root temperature, nitrate, ammonium, potassium, N-deficiency, ion uptake rate, transpiration     

Effects of Root Temperature and Form of Nitrogen Nutrition on Nitrate Reductase Activity in Oilseed Rape (Brassica napus L.)

The effect of root temperature and form of inorganic nitrogensupply on in vitro nitrate reductase activity (NRA) was studiedin oilseed rape (Brassica napus L. cv. bien venu). Plants weregrown initially in flowing nutrient solution containing 10 µMNH₄NO₃ and then supplied with either nitrate or ammonium for15 d at root temperatures of 3, 7, 11 or 17 °C. Shoot temperatureregime was similar for all plants; 20/15 °C, day/night.Root NRA was highest when roots were grown at 3 and 7 °C.In laminae and petioles NRA was highest when roots were 11 or17 °C. The plants supplied with ammonium had much lowerlevels of NRA in roots after 5 d than the plants supplied onlywith nitrate. NRA in the laminae of plants supplied with ammoniumwas low relative to that in plants supplied with nitrate onlywhen root temperature was 11 or 17 °C. Values of the apparent activation energy (E_a) of NR, calculatedfrom the Arrhenius equation, in laminae and petioles were differentfrom roots suggesting difference in enzyme conformation. Evidencethat the temperature at which roots were growing affected E_awas equivocal. Oilseed rape, Brassica napus L., activation energy, ammonium, Arrhenius equation, nitrate, root temperature, nitrate reductase     

表达核糖核酸酶基因的雄性不育油菜的获得

从细菌Ｂａｃｉｌｌｕｓａｍｙｌｏｌｉｑｕｅｆａｃｉｅｎｓ染色体ＤＮＡ中克隆了ＲＮａｓｅ（ｂａｒｎａｓｅ）基因,构建了ＴＡ－２９基因５＇调控区（－１３００－＋３）与ｂａｒｎａｓｅ基因的嵌合基因,通过农杆菌介导的遗传转化,获得了“双低”甘蓝型油菜“中双８２１”的转基因植株。转化植株与末转化植株在高度、生长速度、花器形态、花色等方面基本相同,但转化植株花丝短小、花药干瘪、没有花粉;自花授粉或以其为父本进行的异花授粉均不能结实,表现为完全的雄性不育。花药的横向解剖结构表明：转基因油菜雄性不育与绒毡层细胞的破坏有关     

Development of Oilseed Rape Buds, Flowers, and Pods In Vitro

A technique for growing buds, flowers, and pods of oilseed rape(Brassica napus L. cv. Haplona) on stem explants in vitro hasbeen developed. Open flowers and young pods underwent normaldevelopment on a basal medium of minerals, vitamins, and sucrosebut the development of buds was less successful. Young buds(3 mm long) did not develop and only limited development ofthe older buds (5 mm long) took place. Some 3 mm-long buds wereinduced to develop to open flowers by adding naphthyl aceticacid or gibberellic acid. Pod and seed set in open flowers werenot affected by adding plant growth substances to the medium,but pod elongation and pod dry weight were promoted by gibberellicacid, 105 M, and benzyl amino purine, 10⁷ M, respectively. Reducingthe supply of sucrose or minerals to open flowers reduced seedset, pod elongation and pod weight but did not affect pod set.The physiological significance of the results is discussed. Key words: In vitro cultures, oilseed rape, pod development, flower development