Nitrate and ammonium absorption by plants growing at a sufficient or insufficient level of phosphorus in nutrient solutions

Summary Absorption of nitrate and ammonium was studied in water culture experiments with 4 to 6 weeks old plants of barley (Hordeum vulgare L.), buckwheat (Fagopyrum esculentum L. Moench) and rape (Brassica napus L.). The plants were grown in a complete nutrient solution with nitrate (5.7±0.2 mM) or nitrate (5.6±0.2 mM) + ammonium (0.04±0.02 mM). The pH of the nutrient solution was kept at 5.0 using a pH-stat. It was found that phosphorus deficiency reduced the rate of nitrate uptake by 58±3% when nitrate was the sole N source and by 83±1% when both nitrate and ammonium were present. The reduction occurred even before growth was significantly impeded by P deficiency. The inhibition of the uptake of ammonium was less,i.e. ammonium constituted 10±1% of the total N uptake in the P sufficient plants and 30±5% in the P deficient plants. The reduction of nitrate absorption greatly decreased the difference between the uptake of anions and cations. It is suggested that P deficiency reduced the assimilation of NO ₃ ^– into the proteins, which might cause a negative feedback on NO ₃ ^– influx and/or stimulate NO ₃ ^– efflux.     

苦荞R2R3-MYB转录因子调控原花青素生物合成的研究

基于苦荞花期转录组数据,该研究筛选并克隆获得一个黄酮代谢相关的MYB类转录因子,并命名为FtMYB23。该基因ORF框长879bp,编码292个氨基酸;系统进化树分析显示,FtMYB23与SG5-MYB亚家族成员聚为一簇,属于典型的R2R3-MYB型转录因子。β-半乳糖苷酶滤纸分析表明,其具有转录激活活性。FtMYB23过表达转基因拟南芥株系的表型分析表明,3个阳性株系的种皮颜色均呈现出比野生型更深的褐色,其叶中原花青素含量均极显著增加(P 0.01),分别为野生型的4.68、3.5和2.8倍。qRT-PCR分析表明,转基因拟南芥中黄酮合成相关的AtCHS、AtCHI、AtF3H、AtF3′H、AtFLS、AtDFR和AtBAN等基因的表达量显著升高(P 0.05),而AtTT12的表达量极显著降低(P 0.01)。研究认为,FtMYB23作为典型的Subgroup5-MYB(SG5-MYB)激活型转录因子,通过促进黄酮合成途径早期关键酶基因的表达,从而提高原花青素的合成与积累。     

Intra- and interspecific phylogeny of wild Fagopyrum (Polygonaceae) species based on nucleotide sequences of noncoding regions in chloroplast DNA

The intra- and interspecific phylogeny of Fagopyrum (Polygonaceae) species was studied using nucleotide sequence data from two noncoding regions in chloroplast DNA, the trnK (UUU) intron and the trnC (GCA)-rpoB spacer. Thirty-seven accessions of ten species and two unidentified samples in the urophyllum group of Fagopyrum were analyzed. Both of the studied regions showed high variability, including nucleotide substitutions, insertion/deletions, and inversions. Separate parsimony analyses of the two regions generated phylogenies that were largely consistent with each other. A single most parsimonious tree derived from the combined data of the two regions suggested that (1) either F. statice or F. leptopodum was derived from the ancestor more than once, (2) F. gracilipes, a tetraploid species, has recently been derived from diploid ancestor and rapidly spread out to its present distribution areas, and (3) F. pleioramosum, F. macrocarpum, and F. callianthum, three newly discovered species endemic to the upper Min River valley, differentiated from their common ancestral species in the present distribution area.     

苦荞转录因子基因FtbHLH4的克隆及其对非生物胁迫的应答

根据苦荞花期转录组数据,克隆得到1个苦荞bHLH类转录因子基因,命名为FtbHLH4。采用实时荧光定量PCR技术,分析了非生物胁迫对苦荞芽期FtbHLH4基因表达的影响。序列分析表明,苦荞FtbHLH4基因DNA全长1 852bp,由7个外显子和6个内含子构成,符合GT-AG剪接原则;cDNA序列包含1个1 062bp的开放阅读框,编码353个氨基酸,具有bHLH类蛋白典型的螺旋-环-螺旋保守结构域。在脱落酸(ABA)、NaCl和PEG模拟干旱胁迫下,苦荞芽期FtbHLH4基因表达量均持续上升,至48h时达最大,分别为胁迫前的11.3倍、12.0倍和6.1倍。而在冷胁迫和UV-B胁迫下,苦荞芽期FtbHLH4基因表达量迅速下降,分别于6h和12h降低至胁迫前的24%和23%。研究推测FtbHLH4基因以不同机制参与了苦荞对非生物胁迫的应答过程。     

不同品种苦荞麦不同器官总黄酮含量的比较分析

Total flavonoids content in stems,leaves and seeds of seven cultivars of Fagopyrum tataricum(L.) Gaertn.and a cultivar of F.esculentum Moench were determined by UV-visible spectrophotometry.The results show that total flavonoids content in leaves is higher.Total flavonoids content among different cultivars of F.tataricum has a great difference.Among seven cultivars of F.tataricum,total flavonoids content is the highest in leaves and seeds of ’Jiande Tartary Buckwheat’ with 106.16 and 24.09 mg·g-1,respectively,and in stems of ’Dingbian Tartary Buckwheat’ with 34.65 mg·g-1.The comprehensive analysis result indicates that ’Jiande Tartary Buckwheat’ is the best germplasm resources of F.tataricum and worth to further extension.     

Pb hyperaccumulation and tolerance in common buckwheat (Fagopyrum esculentum Moench)

Common buckwheat grown in Pb-contaminated soil was found to accumulate a large amount of Pb in its leaves (8,000 mg/kg DW), stem (2,000 mg/kg DW), and roots (3,300 mg/kg DW), without significant damage. This indicates that buckwheat is a newly recognized Pb hyperaccumulator, which is defined as a plant containing over 1,000 mg/kg of Pb in its shoots on a dry-weight basis. Moreover, it was shown that application of the biodegradable chelator methylglycinediacetic acid trisodium salt at concentrations of up to 20 mmol/kg resulted in a more than five times higher concentration of Pb in the shoot without notable growth inhibitation at up to 10 mmol/kg. These results indicate that buckwheat is a potential phytoremediator of Pb-contaminated soils.     

野生资源植物金荞麦离体快繁技术研究

针对金荞麦野生资源开发利用情况,试验以茎段为外植体,系统地探讨了以组织培养为手段进行快速繁殖的途径。结果发现：①外植体用HgCl2的消毒时间为6 min;②初代培养时培养基可选择MS＋1.0 mg/L6-BA＋0.5 mg/L NAA＋30 g/L蔗糖;③继代培养时培养基可选择MS＋1.0 mg/L 6-BA＋0.2 mg/L NAA＋30 g/L蔗糖;④生根培养时培养基可选择MS＋0.5 mg/L NAA＋20 g/L蔗糖。     

Characterization of heat-induced aggregates of globulin from common buckwheat (Fagopyrum esculentum Moench)

Some physicochemical properties and the microstructure of heat-induced aggregates of globulin from common buckwheat (Fagopyrum esculentum Moench) (BWG) formed at 100 °C in 0.01 M phosphate buffer containing 1.0 M NaCl, pH 7.4 were studied. Differential scanning calorimetric (DSC) analysis shows a re-distribution of native and extensively denatured proteins in the heat-induced aggregates of BWG, particularly in the ISA fraction. Sodium dodecyl sulfate polyacrylamide gel electrophoretic (SDS-PAGE) analysis suggests the occurrence of both dissociation and association of molecules and the involvement of intermolecular disulfide linkages during thermal aggregation. Transmission electron microscopy (TEM) reveals that native BWG appeared as uniform compact globules with diameters ranging between 11.7 and 12.5 nm. TEM examination of the buffer-soluble aggregates, fractionated by sucrose density gradient ultracentrifugation, demonstrates the formation of strand-like small aggregates and large compact globular soluble macroaggregates.     

不同基因型苦荞幼苗对低磷胁迫的响应

采用沙培法,以4个不同耐低磷苦荞(Fagopyrum tataricum(L.) Gaertn)品种为材料,设正常磷处理(P1,2 mmol/L对照)、低磷胁迫(P2,1 mmol/L)和极低磷胁迫(P3,0.2 mmol/L) 3个处理,研究低磷胁迫对苦荞苗期农艺性状、生理生化指标以及植株磷利用的影响。结果显示:(1)低磷胁迫下,苦荞苗期株高、茎粗、叶面积、地上部干重、根系干重、根系平均直径、根系表面积、根系体积等指标均有所下降;主根伸长、根冠比有所升高,但不同品种的升降幅度有所不同。(2)低磷胁迫使苦荞叶绿素含量、可溶性蛋白含量和根系活力均有所下降,根系的SOD活性、POD活性、酸性磷酸酶活性、可溶性糖含量、游离脯氨酸含量显著增加,且表现为耐低磷苦荞品种的增幅大于不耐低磷苦荞。(3)低磷胁迫使苦荞植株全磷含量和单株磷积累量下降,却使磷利用效率升高。研究结果表明耐低磷品种通过主根伸长下扎以及分泌较多的酸性磷酸酶,合理吸收与利用土壤磷素,通过保持叶片较高的叶绿素含量维持较强的光合能力,通过保持较高的抗氧化酶活性降低膜脂过氧化伤害,最大程度的适应低磷环境。     

荞麦籽粒结构的观察与分析

从荞麦籽粒的和分析中可以看出,荞麦的果皮和种皮容易分开,种子中心巨大的“Ｓ”形胚芽、胚根以及糊粉层虹适量科贮藏蛋白质存在的主要场所。在“Ｓ”形胚芽和胚根两侧是荞麦的两片叶子,由淀粉贮藏细胞组成。该细胞呈长方多棱体,细胞壁极薄且透明,人淀粉粒呈多面球形,大小均匀整齐,淀粉粒间结合紧密、严实,具有一定的几何构形。在淀粉粒间未发现基质蛋白质。