山罗花和天柱山罗花四个居群的数值分析

对山罗花和天柱山罗花的4个居群的15项形态特征进行了数值分析。结果表明:形态性状在4个居群间均存在一定程度的变异,居群间变异系数的平均值从小到大排列为:天柱山居群(天柱山罗花)、天柱山居群(山罗花)、黄山居群(山罗花)、鹞落坪居群(山罗花);天柱山罗花与山罗花种间的形态差异已达到极显著水平,山罗花的3个居群间部分性状也具有极显著的形态差异;以形态特征为基础的Q-聚类分析可以把天柱山罗花和山罗花聚为两类,但山罗花(天柱山居群)和其他2个居群在较远处聚在一起,R-聚类分析发现了强正相关关系、弱正相关关系、弱负相关关系的性状。     

西部某些根瘤菌的数值分类和16S rDNA PCR-RFLP分析

选用61株分离自我国西北地区的野豌豆、棘豆、苜蓿和草木樨根瘤菌和4株已知参比菌株,进行了营养利用、抗生素抗性和耐逆性等13个表型性状研究,通过MINTS软件分析,得到了数值分类树状图,发现全部供试菌株在79％的相似性水平上,分为5个群。对57株未知菌株和10株参比菌株16SrDNAPCR－RFLD分析,发现共具有20个遗传图谱类型,聚类分析树状图表明所有菌株共分为5个系统发育分支,与数值分类结果有较好的一致性。     

繁缕核糖体失活蛋白基因克隆及序列分析

采用同源克隆结合RACE法,克隆了繁缕核糖体失活蛋白的全长cDNA,命名为q3(GenBank accession GQ870262)。序列分析结果表明,q3的开放阅读框(ORF)长780 bp,编码259个氨基酸。序列G+C含量为41.5%,与大部分Ⅰ型RIP基因相近。q3编码的蛋白质命名为Q3,理论分子量为28.16 kD,pI为9.44,均与Ⅰ型核糖体失活蛋白相近;包含由23个氨基酸组成的信号肽。功能结构域分析发现,该蛋白含有3个蛋白激酶磷酸化位点、4个络氨酸蛋白激酶磷酸化位点和7个N-肉豆蔻酰化位点。三级结构预测发现,有35.52%的氨基酸残基参与了α螺旋,24.32%的氨基酸残基组成延伸链,40.15%的氨基酸残基随机缠绕其中。基于繁缕及其近缘种核糖体失活蛋白的氨基酸序列构建的系统发育树显示,其结构与经典分类结果基本一致。     

繁缕和鹅肠菜的花维管束系统比较解剖学研究及其系统学意义

运用石蜡制片技术,对繁缕（Stellaria media）和鹅肠菜（Myosoton aquaticum）的花维管束系统进行了比较解剖观察,为其系统分类提供了一定的科学依据。研究结果表明,两者维管系统有以下特征：（1）花梗部维管束以3束不封闭成环形式分布在中央区。（2）花梗顶部维管束形成一个封闭的分生组织环。（3）分生组织环最先呈辐射状分离出的外层10束,每相隔一个束的那个束向外分裂出2束。其中15束是通往花萼的维管束,5束是通往花瓣的维管束。通往花瓣的5束维管束又一分为二,变成10束花瓣维管束。（4）分生组织环再呈辐射状分裂出10束,形成雄蕊维管束。（5）在子房室区分生组织环再呈辐射状分裂出4子房隔膜束,每束分裂出3束,形成胎座维管束,其数目为12束,每一束均与一个胚珠相连,从而使子房壁维管束数目增加到16束。鉴于繁缕和鹅肠菜花维管束系统的高度一致,将鹅肠菜置于繁缕属比较恰当。     

Modelling the germination of Stellaria media using the concept of hydrothermal time

The germination characteristics of Stellaria media (common chickweed) were investigated over a range of constant temperatures and degrees of moisture stress in order to assess the suitability of hydrothermal time as a basis for modelling germination under field conditions. Maximum percentage germination occurred over a much narrower temperature range around the optimum temperature than previously seen for cultivated crop seed. The entire final percentage germination response to temperature in water was well described by two probit curves, and this model was extended to describe the data at all water potentials at a temperature close to the optimum. The implications of the reduction in germination at nonoptimal temperatures are discussed with respect to the interpretation of germination progress curves and conditional dormancy. After adjusting for maximum percentage germination, a hydrothermal time model was found to fit the data set well within the conditions normally encountered in horticultural seedbeds. This separation of the final percentage germination presents a flexible modelling approach that allows for the different levels of dormancy typically expressed within weed populations. By contrast with many previously reported species, S. media had a synchronous germination rate within the population at any given temperature/water potential combination. This synchronous germination of at least a proportion of the population over a wide range of temperature and water potentials might have ecological significance for the opportunistic germination behaviour of this weed species.     

Nitrate and reduced-N concentrations in the xylem sap of Stellaria media, Xanthium strumarium and six legume species

Abstract At an applied nitrate concentration of 1 mol m^?3, the proportion of xylem sap nitrogen as nitrate was < 15% for Cajanus cajan, Lupinus albus and Trifolium repens, 33% for Pisum sativum and within the range 57–62% for Glycine max, Phaseolus vulgar is, Stellaria media and Xanthium strumarium. At an applied nitrate concentration of 10 mol m～³ the value had increased to 66% for T. repens while at 20 mol m^?3 nitrate values had increased to 46, 51 and 49% for C. cajan, L. albus and Pisum sativum, respectively, and 89% and 85% for 5. media and X. strumarium, respectively. Glycine max and Phaseolus vulgaris differed from the other species in that the proportion of their xylem sap nitrogen as nitrate remained constant (～ 60%) as applied nitrate concentration increased from 1 to 20 mol m^?3. The proportion of total plant nitrate reductase activity in the shoot of C. cajan, S. media and X. strumarium increased as applied nitrate concentration increased from 1 to 20 mol m^?3. Values at the lower and upper concentrations were, respectively, 26 and 72% for C. cajan. 48 and 80% for X. strumarium and 68 and 87% for S. media. The partitioning of nitrate assimilation between root and shoot in these species is discussed.     

Calcium transport across plasma membrane vesicles isolated from shoots of Stellaria media and Arena sativa

Plasma membrane vesicles (ca 40% inside-out, after one freeze-thaw cycle) were extracted and purified from the shoots of oat ( Avena sativa L. ) and chickweed ( Stellaria media L.) using the two-phase aqueous polymer technique. In the presence of ATP or GTP, a rapid uptake of ⁴⁵Ca²⁺ occurred (0.77 and 0.62 nmol Ca²⁺ mg^-1 protein, for ATP and GTP, respectively, in oat, and 0.53 and 0.51 nmol Ca²⁺ mg^-1 protein, for ATP and GTP, respectively, in chickweed). Nucleotide-dependent Ca²⁺-transport was sensitive to 1 μ M Erythrosin B (with ATP. inhibited by 52% in oat and in chickweed by 72%; with GTP, inhibition was similar in both species at ca 67%); ATP-dependent uptake was greater in oat than in chickweed, but not stimulated by calmodulin. Addition of the calcium ionophore A-23187 resulted in the release of label from the vesicles (41% and 63% release with ATP, and 24% and 52% release with GTP, in oat and chickweed, respectively). The results obtained suggest that Ca²⁺-transport is independent of the proton pump. In oat, kinetic data indicate a discontinuity in the absorption isotherm at 10 μ M free calcium.     

深圳湾红树林引种海桑、无瓣海桑的生态评价

对深圳湾红树林引种的外来种海桑(Sonneratia caseolaris (L．) Engl．)和无瓣海桑(S．apetala B．Ham．)的生态适应性、扩散现状及生态入侵的可能性进行了研究。结果表明：海桑和无瓣海桑对深圳湾的气温、盐度、潮滩与土壤等基本适应,虽然极端低温是其生长定居的限制因子,但其子代的抗寒性逐渐增强,在局部区域有一定的繁殖力和扩散力,生态效益明显。从种群生物生态学特性、生态位理论、群落更新理论等方面分析认为,海桑和无瓣海桑在深圳湾造成生态入侵的可能性不大。     

Influence of cucumber mosaic virus infection on the growth response of Portulaca oleracea (purslane) and Stellaria media (chickweed) to nitrogen availability

The study characterized the influence of cucumber mosaic virus (CMV) on the growth response of two annual weeds to nitrogen. Plants were grown individually along a N gradient from 4 to 32 mmol l⁻¹ and data were interpreted using growth analysis. Plant biomass increased with N concentration and was significantly higher for healthy than infected plants at the two highest N concentrations. Healthy plants of Portulaca oleracea L. were characterized by lower biomass allocation to leaves and higher biomass allocation to roots than infected plants; no change in biomass allocation was recorded for Stellaria media Vill. Relative growth rate ( rgr ), net assimilation rate ( nar ) and specific leaf area ( sla ) of plants increased with increasing N concentration. Healthy plants of P. oleracea were characterized by a higher rgr and nar and a lower sla than infected plants, whereas healthy S. media had a higher rgr but a similar nar and sla or leaf weight ratio ( lwr ) compared with infected plants. The consequences of these results on the population dynamics of weeds and virus spread are discussed.     

Isolation, molecular cloning and antimicrobial activity of novel defensins from common chickweed (Stellaria media L.) seeds

Two novel highly homologous defensins, Sm-AMP-D1 and Sm-AMP-D2, were isolated from seeds of common chickweed Stellaria media L. (family Cariophyllaceae). They show sequence homology to defensins of the Brassicaceae plants and display strong inhibitory activity against phytopathogenic fungi and oomycetes in the micromolar range (IC₅₀ ≤ 1 μM). The cDNA sequences coding for Sm-AMP-D1 and Sm-AMP-D2 were obtained. They code for highly homologous precursor proteins, consisting of a signal peptide of 32 amino acid residues and the mature peptide domain of 50 amino acid residues. The Sm-AMP-D1 and Sm-AMP-D2 precursors differ by two amino acids: one in the signal peptide region, and the other, in the mature peptide domain. Two Sm-D1-encoding genes were identified in S. media genome by PCR amplification from the genomic DNA using Sm-D1-specific primers. They contain a single 599-bp intron in the signal peptide domain and differ from each other by nucleotide substitutions in the intron and 3′-untranslated regions, while the coding sequences are well conserved. One of the genes matched perfectly the sm-D1 cDNA sequence. The sm-D genes show promise for engineering pathogen resistance in crops and expand our knowledge on weed genomics.