Effects of kangaroo rat exclusion on vegetation structure and plant species diversity in the Chihuahuan Desert

Long-term (1977–90) experimental exclusion of three species of kangaroo rats from study plots in the Chihuahuan Desert resulted in significant increases in abundance of a tall annual grass (Aristida adscensionis) and a perennial bunch grass (Eragrostis lehmanniana). This change in the vegetative cover affected use of these plots by several other rodent species and by foraging birds. The mechanism producing this change probably involves a combination of decreased soil disturbance and reduced predation on large-sized seeds when kangaroo rats are absent. Species diversity of summer annual dicots was greater on plots where kangaroo rats were present, as predicted by keystone predator models. However, it is not clear whether this was caused directly by activities of the kangaroo rats or indirectly as a consequence of the increase in grass cover. No experimental effect on species diversity of winter annual dicots was detected. Our study site was located in a natural transition between desert scrub and grassland, where abiotic conditions and the effects of organisms may be particularly influential in determining the structure and composition of vegetation. Under these conditions kangaroo rats have a dramatic effect on plant cover and species composition.     

Effect of Intracellular Glutathione Level on the Production of 6-Methoxymellein in Cultured Carrot (Daucus carota) Cells

To produce phytoalexin, 6-methoxymellein (6-MM) was induced in suspension cultures of carrot (Daucus carota) by buthionine sulfoximine (BSO) and CuCl2. Addition of BSO (a specific inhibitor of glutathione [GSH] synthesis) to the cultures lowered the cellular GSH levels. This depletion of GSH was BSO-concentration dependent, and the extent of 6-MM accumulation was dependent on the GSH depletion. The accumulation of 6-MM induced by BSO was suppressed by exogenous GSH. Exogenous H2O2 stimulated the production of 6-MM when added 1 d after BSO treatment, whereas H2O2 added at time zero or on the 4th d of BSO treatment did not. Moreover, a synergistic effect of simultaneous addition of BSO and CuCl2 was observed. These results suggest that active oxygen species may be involved in the triggering of 6-MM synthesis.     

Fertile plants regenerated from suspension culture-derived protoplasts of an indica type rice (Oryza sativa L.)

Calluses were induced from immature embryos of an indica type rice and finely dispersed cell suspension cultures were initiated from the callus using modified AA medium (S₁ medium). The suspension cultures were maintained alternatively (1–2 passages in each medium) in S₁ medium and S₂ medium, the latter containing KNO₃, NH₄NO₃, proline and glutamine as nitrogen source. Protoplasts of high quality were isolated form suspension cells cultured in S₂ medium supplemented with ABA. Embedding the protoplasts in agarose blocks containing NH₄NO₃-free modified KM8P(PM₁) medium and immersing the blocks in NH₄NO₃-containing modified KM8P(PM₃) medium were most effective for obtaining protoplast division and callus formation. The protoplast-derived calluses were precultured in potato extract-aand/or ABA-containing N₆(D₁, D₂ or D₃) media and many embryo-like structures were formed. These structures developed into plantlets after being transferred to N₆ differentiation (D₄) medium. The regenerated plantlets grew into mature plants and beard seeds normally.Abbreviations AA medium amino acids based medium - ABA abscisic acid - BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - DF division frequency - IAA indoleacetic acid - KIN kinetin - NAA naphthaleneacetic acid - PE planting efficiency     

黄麻栽培种圆果种×长果种的种间杂交研究

１９８９—１９９１年对黄麻栽培种圆果种（Ｃｏｒｃｈｏｒｕｓｃａｐｓｕｌａｒｉｓ）和长果种（Ｃ．ｏｌｉｔ－ｏｒｉｕｓ）选用了具有不同茎色和腋芽性状的材料做了６个组合,获得１３４株杂种Ｆ＿１苗。但苗株发根不良,在移栽后两周陆续死亡,最后幸存ＲＲ－５×（ＢＬ×７７－１９）Ｆ＿１组合中两株植株并开花、结果。Ｆ＿１均有腋芽,表现为父本的性状;花果形状偏向母本;茎色红同双亲。这两株的Ｆ＿２,茎色和腋芽性状分离成４种表现型：红茎或青茎有腋芽及红茎或青茎无腋芽。其中红茎有腋芽的生长较快。对种间杂交技术、亲本间的花粉与柱头亲和性、杂交花的胚珠受精情况及染色体构型等方面也作了观察、研究。     

伪狂犬病毒闽A株基因文库的构建及物理图谱分析

本文报道以质粒ｐＢＲ３２２作载体,用鸟枪法克隆出了ＰＲＶ闽Ａ株除ＢａｍＨＩ－１,２外的所有酶切片段,构建了ＰＲＶ闽Ａ株基因文库,并以克隆出的ＢａｍＨＩ片段用光生物素标记作探针,应用分子杂交法确定了ＰＲＶ闽Ａ株绝大部分限制性内切酶位点的位置。     

槟榔（Areca catechu L.）的民族植物学

本文从民族植物学的观点介绍了我国南方各省嚼槟榔的习俗、历史及演变,分析了这个习俗的形成原因及槟榔的药用价值。作者认为咀嚼槟榔有成瘾性,但是否对人的中枢神经系统有损害,必须进一步研究。作者对这种习俗提出了几点看法和建议,对槟榔的开发利用有重要参考价值。     

中国稻蝗属细胞分类学研究(英文)

本文对分布于中国境内11省区,27个采集地点的八种稻蝗进行了染色体C带核型比较研究。结果表明:中华稻蝗Oxya chinensis,上海稻蝗O.shanghaiensis,无齿稻蝗O.adentata C带分布型式相似,但染色体分组型式、交叉定位数据以及异染色质含量具有差异;山稻蝗O.agauisa具有本身独特的带纹结构,与本属其它种类迥异;双带稻蝗O.bicingula染色体带型结构相似于山稻蝗及中华稻蝗类群,表明三者在进化历程中有一定联系。小稻蝗O.hyla intricata中一个亲缘种团(Sibling species group),体现在种内的形态差异及染色体带型结构的不同。显示该种近期内分化速率较高。据此,本文讨论了稻蝗属内八个种相互间的亲缘关系和分类地位,本文认为稻蝗属内务物种进化速率是不均衡的,这种状态应归因于各物种的遗传背景和环境因素的影响。     

BRCA1 maps proximal to D17S579 on chromosome 17q21 by genetic analysis

Previous studies have demonstrated linkage between early-onset breast cancer and ovarian cancer and genetic markers on chromosome 17q21. These markers define the location of a gene (BRCA1) which appears to be inherited as an autosomal dominant susceptibility allele. We analyzed five families with multiple affected individuals for evidence of linkage to the BRCA1 region. Two of the five families appear to be linked to BRCA1. One apparently linked family contains critical recombinants, suggesting that the gene is proximal to the marker D17S579 (Mfd188). These findings are consistent with the maximum-likelihood position estimated by the Breast Cancer Linkage Consortium and with recombination events detected in other linked families. Linkage analysis was greatly aided by PCR-based analysis of paraffin-embedded normal breast tissue from deceased family members, demonstrating the feasibility and importance of this approach. One of the two families with evidence of linkage between breast cancer and genetic markers flanking BRCA1 represents the first such family of African-American descent to be reported in detail.     

白粒济宁3号小麦品种的选育

用快中子照射红粒济宁3号小麦干种子,后代获得白粒植株,经选育而成白粒济宁3号。白粒济宁3号与红粒济宁3号比,除籽粒颜色差别外,籽粒蛋白含量显著高于红粒济宁3号,而落黄性、籽粒饱满度、千粒重、产量均略低于红粒济宁3号,该品种累计种植面积10余万亩。     

番茄种子经激光和咖啡因处理后其当代生物效应的研究

咖啡因具有抑制一些酶的活性,可减弱或消除生物体自身对激光引起的生物效应的修复作用。试验证明咖啡因对番茄种子萌发有强烈的抑制作用,咖啡因和激光复合处理生物效应显著,可降低番茄种子的发芽,并促进番茄果实增大和生长前期速率加快。