In vitro development of wheat (Triticum aestivum L.) from zygote to plant via ovule culture

Ovules of the wheat breeding line Veery #5 were excised and transferred to culture within 24 h after pollination. When ovules were cultured on Phytagel-solidified medium, and the pericarp removed exclusively at the micropylar tip and the abaxial side, zygotes from up to 79.2% of the ovules underwent embryogenesis with the same developmental pattern as found in planta. Embryos from more than 50% of the cultured ovules germinated when transferred to regeneration medium. More than 100 plantlets were randomly chosen for transfer to soil, all of which developed to phenotypically normal and fertile plants. With this system, the entire process of zygotic embryogenesis can be studied using living material. Furthermore, the method could be used as an embryo rescue technique for plant breeding purposes. Received: 17 June 1996 / Revision received: 22 October 1996 / Accepted: 15 December 1996     

Cytological Evidences of a Possible Mode of Nurture Absorption of the Differentiating Embryo in Triticum aestivum

Coleorhiza covered the radicle of differentiating wheat embryo and morphologically appeared as tapered tissue with an attached globular protrusion. In the early phase of differentiation a series of structural changes occurred at some local areas of the coleorhiza. By light and electron microscopic inspections combined with fluorescence labelling it was uncovered that cells of the peripheral layers of the globular protrusion and the neck region underneath gradually exhibited degeneration and disintegration while a lot of broken plasmodesmata still remained at the boundary wall of the inner surviving cells. Impermeable fluorescence probe 4.3 kD FITC- dextran could enter these living cells and continuously diffuse to their neighborhood. All these showed that a direct communication was estabhshed between the symplasm of coleorhiza and the external medium and the remaining plasmodesmata, though broken in one end, might function as symplasmic pathway for external material incorporation. Analyzing the above described results a possible mode of nurture absorption of differentiating embryo then could bo recognized; particularly, comparing with the globular pretmsion the limited area of the neck region towards dorsal side might play a more important role in nurture absorption of the young embryo. Temporal and partial disintegration of the neck region and consequential regeneration in situ and increase of plasmodesmatal conductivity in the surrounding surviving cell group were most favourable to the incorporation and intercellular translocation of the external material for the coleorhiza. A large quantity of nutrients intruding into the coleorhiza at proper instant through the transiently opened route would effectively coordinate with the need of embryo differentiation without leaving apparent destruction to the coleorhiza.     

Effect of 2,4-D on Seedling Physiology and Cytogenetical Studies in Triticum aextivum and Phalaris minor(Gramineae)

Effects of 2, 4 -D on seedling growth and chromosomal abnormalities were studied in Triticum aestivum and Phalaris minor. Seeds were soaked at different concentrations of 2, 4 -D (0.01%, 0.1%, 1.0%) for 4, 8, 12 and 16 hours. 2, 4 -D suppressed the germination more severely in P. minor than in T. aestivum. Shoot and root length was retarded with the increase of concentration and time of treatment in both species. Generally radical was more negatively affected than coleoptile and emergence of radical was not observed at 1.0% concentration at 8, 12, and 16 hours of treatment in T. aestivum while in P. minor there was a total lack of radical emergence at 1.0% concentration for all durations of treatment. Stiff and curled roots and undifferentiated callus like scutellar tissues were observed in T. aestivum, while in P. minor the coleoptile obtained was lean, pale green in colour and was lying flat on filter paper. Mitotic index decreased, while chromosomal abnormalities, bridges and laggards were increased with the increase of concentration and soaking time however, laggards were not observed in T. aestivum. Clumping and chain formation of chromosomes at metaphase was also noticed in P. minor.     

Efficient callus induction and plant regeneration from mature embryo culture of winter wheat (Triticum aestivum L.) genotypes

Immature and mature embryos of 12 common winter wheat (Triticum aestivum) genotypes were cultured in vitro to develop an efficient method of callus formation and plant regeneration from mature embryo culture, and to compare the responses of both embryo cultures. Fifteen days after anthesis, immature embryos were aseptically dissected from seeds and placed with the scutellum upwards on a solid agar medium containing the inorganic components of Murashige and Skoog (MS) and 2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D). Mature embryos were moved slightly in the imbibed seeds. The seeds with moved embryos were placed furrow downwards in dishes containing 8 mg/l 2,4-D for callus induction. The developed calli and regenerated plants were maintained on 2,4-D-free MS medium. Plants regenerated from both embryo cultures were vernalized and grown to maturity in soil. Regenerated plantlets all maintained the hexaploid chromosome number. A strong genotypic effect on the culture responses was found for both explant cultures. Callus induction rate, regeneration capacity of callus and number of plants regenerated were independent of each other. Mature embryos had a high frequency of callus induction and regeneration capacity, and therefore, being available throughout the year, can be used as an effective explant source in wheat tissue culture. Received: 4 February 1997 / Revision received: 1 April 1997 / Accepted: 5 May 1997     

壳聚糖对镉胁迫条件下小麦生长及生理的影响

以小麦为材料,研究了镉对水培小麦幼苗的胁迫作用及壳聚糖对镉胁迫的缓解效应。结果表明:250μmol·L-1的镉胁迫处理后,小麦幼苗的生长受到严重抑制,叶片中叶绿素含量明显下降,金属硫蛋白和丙二醛的含量显著上升(P<0.05);培养液中添加0.01%的壳聚糖能降低小麦幼苗中镉的积累,对小麦幼苗的镉胁迫具有明显地缓解效应。     

Sucrose metabolism during endosperm development in wheat (Triticum aestivum)

This work reports changes in sucrose synthase and invertase activities throughout endosperm development in wheat, together with the associated substrates and metabolites, sucrose, UDP, glucose, fructose and UDP-glucose. Throughout endosperm development, sucrose synthase had consistently higher activity than invertase and indeed invertase activity did not change appreciably. The observed variation in pattern and amounts of glucose and fructose present during the mid- and late stages of endosperm development confirmed the suggestion that invertase was not the preferred pathway of sucrose catabolism. Kinetic parameters for sucrose synthase were determined in crude extracts. Estimates of UDP and sucrose concentrations suggest that sucrose synthase is unlikely to achieve its potential maximum velocity. This limitation may however be overcome in part by the apparent excess catalytic activity measured during endosperm development.     

Ultrastructural Observations on the Distribution of the Intra-and Intercellular Cytoskeleton of the Endosperm Cells in Triticum aestivum

By means of Triton X-l00 extraction and DGD (diethylene glycol distearate) embedment-free section method the distribution pattern and characteristics of intra- and intercellular cytoskeleton of endosperm cells of Triticum aestivum L. were studied with electron microscopy. Threedimensional architecture of the cytoskeleton could be recognized as a meshwork mainly composed of microtubules (MT) and microfilaments (MF). Attention was stressed on the interface of the adjoining cytoskeletal frameworks where an attractive phenomenon observed was that the MF extruding from the surface of the cytoskeleton often traversed the whole wall boundary and connected the neighbouring frameworks into an entity. In the endosperm tissue two types of transcellular MF distribution could be distinguished, the MF in bundles traversing the enlarged intercellular channels and the MF individually penetrating the wall boundary; that seemed to coordinate with the co-presence of normal and modified plasmodesmata in the same wall. The above observations demonstrated the intercellular cytoskeletal continuity within the symplast and confirmed that the MF was the main constituent of the traversing cytoplasmic strands, the possibility of MF being organized as a structural element of the normal plasmodesmata was also discussed.     

不同浓度硝态氮供应下小麦生长、硝态氮累积及根系钙信号特征

以小麦品种‘石麦15’和‘衡观35’为材料进行营养液水培试验,研究不同浓度硝态氮供应对小麦苗期根系形态、钙离子流特征及钙调蛋白(CaM)含量的影响。结果表明,与适宜浓度硝态氮处理(2.5mmol/L)相比,无外源硝态氮供应时小麦地上部鲜重、硝态氮含量均降低,侧根数量显著减少;高浓度硝态氮处理(50mmol/L)下两个小麦品种地上部硝态氮含量升高,根系总长度降低,‘石麦15’侧根数量减少。无硝态氮和高浓度硝态氮处理下,根系中钙调蛋白含量降低,且‘衡观35’的降低幅度大于‘石麦15’。无外源硝态氮供应时小麦根尖表现出较为明显的钙离子外流特征;与适宜浓度硝态氮处理相比,高硝态氮处理下小麦根尖Ca2+的内流速度显著下降。说明硝态氮供应不足和高浓度硝态氮供应会影响小麦根系生长,根系Ca2+外流或Ca2+内流速度下降,CaM含量减少,Ca2+/CaM可能介导硝态氮调控小麦根系生长发育。     

Gliadin and Glutenin Variation in Seeds of Somaclones of Triticum aestivum

Gliadin and glutenin of seeds of a pollen-derived pure line “H-33” and its 9 stable somaclones of wheat (Triticum aestivurn L.) from inflorescence callus were investigated using SDSPAGE. Among the 9 somaclones 6 were identical to the “H-33” in SDS-PAGE patterns of of gliadin and glutenin. The other 3 somaclones were identical with each other, but different from “H-33”. The varied electrophoretic bands of seed protein showed that somaclonal variation had occured at gene level during tissue culture in which the somaclones were produced.     

尾状山羊草与硬粒小麦,普通小麦的杂交及外源染色质检测

尾状山羊草（AegilopscaudataL．）具有丰富的抗病虫和高赖氨酸、高蛋白优良性状,是进行小麦（TriticumaestivumL．）遗传改良的重要遗传资源。合成了硬粒小麦（TriticumdurumDesf．）-尾状山羊草双二倍体、进行了普通小麦与双二倍体的杂交。并以作者克隆的尾状山羊草C基因组特异重复序列PAeca212为探针,对上述杂交后代的花粉母细胞进行了染色体原位杂交检测。证实了新合成的双二倍体中有7对C基因组染色体;在F2中检测到C基因组染色体的自发纯合易位,显示出从C基因组向小麦转移外源基因的光明前景。     

云南铁壳麦高分子量麦谷蛋白亚基组成及其遗传多样性分析

以36份云南铁壳麦为试验材料,采用SDS-PAGE法分析了Glu-1位点编码的高分子量麦谷蛋白亚基(HMW-GS)及组成。结果表明,在Glu-A1位点上检测到3种(N,2*和1)亚基类型,Glu-B1位点上共检测到5种(7、7 8、17 18、13 16和6 8)亚基类型,Glu-D1位点上只检测到1种(2 12)亚基类型。共检测到6种亚基组成类型,即:N、7、2 12,N、7 8、2 12,2*、7 8、2 12,2*、17 18、2 12,1、6 8、2 12和1、13 16、2 12。云南铁壳麦的HMW-GS为普通小麦已知变异类型的18%,3个位点的Nei's遗传变异系数顺序为Glu-B1(0.5734)>Glu-A1(0.2484)>Glu-D1(0),表明云南铁壳麦属较原始类型,Glu-D1位点未发生变异。品质评分最高分为8分(3份材料),平均为5.2分。同时86%的云南铁壳麦具有适合制作优质手工馒头的高分子量麦谷蛋白亚基(N和2 12),42%的云南铁壳麦具有亚基组成类型(1、7 8、2 12和N、7 8、2 12),这些材料可作为云南小麦馒头品质改良的材料。     

DNA超甲基化在小麦耐盐胁迫中的作用

运用高效液相色谱技术测定小麦(Triticum aestivumL.)耐盐品种‘德抗961’和盐敏感品种‘豫麦34’盐胁迫后叶片和根DNA中5-甲基胞嘧啶百分含量的变化,结果表明,经150 mmol/L NaCl处理6 d后,‘德抗961’叶片和根DNA中的5-甲基胞嘧啶的百分含量显著下降,但经150 mmol/L NaCl处理10 d后,耐盐品种‘德抗961’叶片和根DNA中的5-甲基胞嘧啶的百分含量都比盐敏感品种‘豫麦34’的高。由此推测DNA超甲基化可能是植物耐盐机制的一部分。     

环境因子对小麦体内镉的生物毒性和植物络合素合成的影响

采用水培方式,研究了不同环境因子对小麦体内Cd的生物毒性与植物络合素(PCs)合成的影响.结果表明,Cd胁迫对小麦产生明显的毒害效应,并显著诱导根合成PCs;pH、Ca和S对小麦体内Cd的吸收和生物毒性具有不同程度的影响,根中PCs的诱导量与Cd的生物毒性变化表现一致;供磷减轻了Cd胁迫的生物毒性,根中PCs的诱导量也显著降低;镁对Cd胁迫的生物毒性影响甚微,根中PCs的诱导量和Cd的吸收量均未见明显变化.本实验结果证明Cd对PCs的诱导能力与植物体内Cd的毒性之间存在一定的相关关系,可将PCs作为Cd胁迫的生物标记物.     

冬小麦植物铁载体分泌的杂种效应

缺铁是石灰性土壤常见的植物营养问题之一。禾本科植物种或基因型的植物铁载体分泌能力与耐缺铁有关 ,提高植物铁载体分泌能力是改良缺铁的土壤上植物铁营养的关键措施之一。在水培条件下分析了冬小麦(TriticumaestivumL .) 3个杂交种及其 4个亲本在缺铁营养液中植物铁载体的分泌及杂种的效应。植物铁载体的分泌率通过根分泌物对新形成的Fe(OH) 3 的活化能力进行测定 ,在缺铁症出现时每隔 2、3天测定 1次。在缺铁条件下 ,所有基因型都分泌较多的植物铁载体 ,并且随缺铁症状的发展分泌量增加。杂交种具有对缺铁更敏感的反馈系统 ,在缺铁条件下 ,杂交种比亲本分泌铁载体的速度更快、量更高。通过分析杂交种和亲本的关系 ,认为可以通过对亲本分泌植物铁载体能力和配合力的选择 ,利用杂种优势来提高小麦铁的利用效率。     

Hybridization of Aegilops caudata with Triticum durum,Triticum aestivum and the Detection of Alien Chromatins

Aegilops caudata L. carries resistance genes against wheat diseases as well as genes of high crude protein and lysine contents, which can be useful for wheat improvement. An amphiploid of Triticum durum - Ac. caudata was synthesized and the hybridization of T. aestivum with the amphiploid Am 8 was carried out. Chromosome in situ hybridization was carried out for the PMC (pollen mother cell) of the synthesized amphiploid (AABBCC) and ( T. aestivum Beijing 837 × Am 8) F2 by using the pAeca 212 as a probe. The results showed that the 7 bivalents from C genome had hybridization signals in the amphiploid. The detection for F2(Beijing 837× Am 8) indicated that translocation, even (pure) home translocation, occurred in F2 generations spontaneously. The study showed the bright prospect in transferring alien resistance genes from C genome to wheat.     

Nickel toxicity and peroxidase activity in seedlings of Triticum aestivum L.

Ni²⁺ toxicity was evaluated in Triticum aestivum L. by its effects on root and shoot length, dry matter production and water content. Over a threshold value of 20 mmol m^?3 Ni²⁺ the degree of toxicity increases as a function of the Ni²⁺ concentration in the medium. Ni²⁺-treated roots show enhanced lipid peroxidation; the higher Ni²⁺ treatment (40mmol m^?3) also increases leakage of K⁺. In roots and shoots, Ni²⁺ enhances both guaiacol and syringaldazine extracellular peroxidase activity. The increase in extracellular peroxidase activity is also associated with an increase in the phenolic contents of roots and shoots. The observed growth inhibition might be partly the result of the effect of Ni²⁺ on cell turgor and cell-wall extensibility. Intracellular soluble peroxidases are also stimulated by Ni²⁺; such effects, independently of the substrate, were detected in extracts of Ni²⁺-treated shoots at a lower Ni²⁺ concentration than in the roots. Intracellular peroxidases might act as scavengers of peroxide radicals produced as a result of nickel toxicity.     

Fluorescence Microscopic Observations on the Distribution Patterns of Actin Filaments in the Cells of Developing Endosperm in Triticum aestivum

The presence and distribution patterns of actin filaments (AFs) in the cells of developing wheat (Triticum aestivum L. ) endosperm exhibiting intercellular protoplasmic movement were studied with fluorescence microscopy and video microscopy. By using TRITC-PhaIloidin as fluorescence probe and cytochalasin B (CB) treatment it was uncovered that there were a lot of AFs scattered throughout the cytoplasm and the patterns of AFs varied greatly with the actin localization. Four configurations of AFs could be recognized: an actin meshwork surrouding the nucleus; bundles of AFs radiating from nuclear “basket” and extending to the periplasm; numerous finer AFs densely and randomly distributed in the cortical cytoplasm and fusiform bodies composed of AFs appearing in the endosperm cells lying at the “cheek” of the caryopsis. Judging from the dynamic characters of intercellular movement of the cytoplasmic constituents and the reaction of cytoplasmic strands related to CB treatment, the authors have discussed and proposed that the exhibition of the two kinds of intercellular movement (extrusion of cytoplasmic strands and mass flow of ground substance) might also be in close relation to the different configurations of AF organization in the cytoplasm.     

八倍体小偃麦与不同需水性小麦气孔特性比较研究

在温室大棚中对八倍体小偃麦(TAI 7045、中1)和不同需水性普通小麦(晋麦66、晋麦67、晋麦70和晋太170)开花期的气孔特性进行了比较研究.结果表明:正常生长条件下,八倍体小偃麦的气孔频率显著低于高水肥小麦晋麦66(P<0.01),而与中水肥及抗旱性小麦的差异不显著(P>0.05);八倍体小偃麦的光合速率显著高于普通小麦(P<0.05),这种差异主要是由高水肥品种晋麦66造成的,虽然八倍体小偃麦的气孔导度和羧化效率高于普通小麦,但差异不显著;光合速率与气孔频率呈负相关,与气孔导度呈显著正相关.     

Ultrastructural Changes of the Nucleolus During Cell Cycle in Triticum aestivum

The ultrastructural changes of the nticleolus during cell cycle in common wheat (Triticum aestivum L. ) were studied by an "en bloc" silver-staining method. It was observed that in interphase, the nucleolus was heavily stained, within which fibrillar centres, dense fibrillar component, granular component and nucleolar vacuoles could be identified. A large quantity of argentine fine granules were distributed in the condensed chromatin. Dur-ing prophase, along with the disintegration of the nucleolus and condensation of the chromatin, the larger heavily-stained granules gradually appeared at the periphery of the chromatin. At late prophase, the materials derived from the nucleolus were spread and deposited on the surface of the chromosomes. The silver-stained, larger granules, deriving from the disintegrated nucleolus, accumulated at the periphery of the metaphase chromosomes and formed an uneven and discontinuous "sheath"-like structure. This "sheath"-like structure was also observed at anaphase. In telophase, the silver-stained nucleolar materials were progressively separated from the "sheath' and fused with each other to form prenucleolar bodies, and at last, participating in the formation of new nucleoli. The results showed that the nucleolar materials were transferred directly to the surface of the chromosomes and formed a discontinuous coat, but not incorporated into the interior of the chromosomes. The silverstained granules inside the chromosomes were neither related to the nucleolus nor to the materials from the disintegrated nucleolus.     

普通小麦和新麦草属间杂种的产生及细胞遗传学研究

进行了普通小麦和华山新麦草属间杂交,运用杂种幼胚培养技术,首次成功地获得了它们的属间杂种。F_1形态趋于中间型,均完全不育。F_1花粉母细胞预期类型(2n=28)的减数分裂中期Ⅰ平均染色体配对构型为26.72Ⅰ+0.62Ⅱ+0.01Ⅲ,后期Ⅰ和后期Ⅱ有落后染色体,多分体具大量微核。结果表明普通小麦和华山新麦草的染色体组间不存在同源或部分同源性。还观察到花粉母细胞异常减数分裂现象。用普通小麦回交,未获得回交后代。