土壤干旱胁迫对九头狮子草和圆苞金足草幼苗形态和生理特性的影响

采用称重控水法控制土壤相对含水量分别为(85.0±2.5)％(对照)、(67.5±2.5)％(轻度干旱)、(50.0±2.5)％(中度干旱)和(32.5±2.5)％(重度干旱),对土壤干旱胁迫条件下九头狮子草[Peristrophe japonica (Thunb.)Bremek.]和圆苞金足草(Goldfussia pentstemonoides Nees)2年生苗的植株形态及生理特性变化进行了研究.结果表明:经土壤干旱胁迫处理30 d后供试2种植物的外部形态均有一定变化,其中九头狮子草主要变化为叶片失绿、变薄且萎蔫、枝条下垂;圆苞金足草主要变化为茎干倒伏、叶片变软且叶柄低垂.随土壤干旱胁迫程度的增加,供试2种植物叶片的自然饱和亏、临界饱和亏、需水程度、束缚水含量、束缚水与自由水的含量比值、脯氨酸含量和可溶性糖含量均呈逐渐增加的趋势且均高于对照,而自由水含量、最高水势、最低水势和可溶性蛋白质含量均逐渐降低且总体上低于对照.总体上看,在重度干旱胁迫条件下供试2种植物各生理特性均与对照有极显著或显著差异,而在轻度或中度干旱胁迫条件下部分指标与对照无显著差异.供试2种植物各生理指标的变化幅度有明显差异,在同一干旱胁迫条件下九头狮子草叶片的自然饱和亏、需水程度、自由水含量、最高水势和最低水势的降幅、脯氨酸含量和可溶性蛋白质含量的降幅均高于圆苞金足草,其临界饱和亏、束缚水含量、束缚水与自由水的含量比值和可溶性糖含量均低于圆苞金足草.综合分析结果表明:供试2种植物对土壤干旱胁迫均具有一定的耐性,但圆苞金足草具有更强的抵御干旱的生理机制.     

中国竹亚科牡竹属一新种——长耳吊丝竹

描述了竹亚科牡竹属一新种——长耳吊丝竹（Dendrocalamus Iongiauritus S．H．Chen,K．F．HuangetR．S．Chen）。该种与吊丝竹（D．minor（McClure）ChiaetH．L．Fung）相近似,但该竹种部分节有明显发达的一条主枝,箨耳较大,明显并与箨片基部相连,窄长,横卧于箨鞘两肩,且呈有规则皱褶状,并着生有6～8mm长的波曲燧毛,箨舌高达0．7～0．9cm,呈不整齐撕裂状,上部有灰黄色扁形长毛,易于区别。     

Effect of competition intensity on recruitment of palatable and unpalatable grasses

In this study, we made an attempt to reveal how competition intensity from established plants impacts on palatable and unpalatable grass seedlings recruitment, in a natural mesic grassland of central Argentina. Our objective was to assess the seedling recruitment of a palatable species (Chascolytrum subaristatum) and an unpalatable species (Nassella trichotoma) in microsites differing in competition intensity from established plants. Identity (C. subaristatum and N. trichotoma) and defoliation severity were used as surrogate for competition intensity. In March 2017, we permanently marked established individuals of N. trichotoma and C. subaristatum and placed two circular plots adjacent to each individual. In one plot we added seeds of N. trichotoma and in the other seeds of C. subaristatum. After seeding, established plants were randomly assigned to one of three level of defoliation: without defoliation, low defoliation severity and high defoliation severity. From April to November 2017 (i.e. over a complete annual growing cycle), we measured seedling density, recruitment and growth. Our results supported the hypothesis that seedlings of palatable grasses are more competitive than seedlings of unpalatable grasses. Seedling of the palatable grass C. subaristatum recruited successfully regardless the intensity of competition from established plants, whereas seedlings of the unpalatable grass N. trichotoma recruited better under low competitive pressure from established plants. Our results suggest that the availability of microsites with low competitive pressure from the established vegetation, created by selective grazing of palatable grasses, promotes the recruitment of unpalatable grass seedlings. This mechanism may contribute to the species replacement process commonly observed in heavy grazed grasslands.     

模拟低温或自然低温条件下牡竹属3种类抗寒性及生理指标的比较

以牡竹属(Dendrocalamus Nees)的清甜竹(D.sapidus Q.H.Dai et D.Y.Huang)、花吊丝竹[D.minor var.amoenus(Q.H.Dai et C.F.Huang) Hsueh et D.Z.Li]和勃氏甜龙竹[D.brandisii (Munro) Kurz]盆栽苗为实验材料,测定了模拟低温(0℃、-5℃、-10℃、-15℃、-20℃和-25℃)条件下3个竹种离体叶片的相对电导率和伤害率,在此基础上根据Logistic方程推算出3个竹种的低温半致死温度(LT50);对自然低温(15℃、10℃、5℃、3℃、0℃和-2 C)条件下3个竹种叶片的形态变化以及相对电导率、叶绿素和MDA含量及SOD活性的变化也进行了比较分析.结果表明:在模拟低温条件下,3个竹种离体叶片的相对电导率和伤害率均随温度降低逐渐增大,且总体上与对照(25℃)有显著差异(P＜0.05);根据Logistic方程推算出花吊丝竹、勃氏甜龙竹和清甜竹的LT50分别为-3.07℃、-1.83℃和-1.40 C.在日最低温度大于5℃的自然低温条件下3个竹种的叶片均能够正常生长,而随温度降低,叶片逐渐出现水浸斑点、失绿等症状直至干枯脱落,其中清甜竹叶片伤害症状最重;在自然低温条件下,随日最低气温的降低,3个竹种叶片的叶绿素含量总体呈下降趋势、相对电导率则逐渐升高、MDA含量和SOD活性总体上均呈波动的趋势;与日最低气温15℃相比,在日最低气温-2℃条件下清甜竹叶片叶绿素含量和SOD活性降幅最大而花吊丝竹降幅最小,清甜竹叶片相对电导率最高而花吊丝竹最低.根据LT50和叶片形态及生理指标的变化,可确定3个竹种的抗寒性均较差,其中清甜竹的耐寒能力最弱.     

产生鬼臼毒素菌株的诱变选育

目的:提高原始菌株鬼臼毒素的产量,以期组织工业化生产,从而扩大鬼臼类化合物的资源。方法:以交链孢霉Ty为研究对象,进行紫外线和He-Ne激光复合诱变,再对所获得高产菌株进行发酵条件的优化。结果:筛选到一株鬼臼毒素高产菌株Ty4-16-13,产量达4.213μg/L,比原始菌株提高96%。结论:诱变后的菌株经7次传代,产量较稳定,可用于工业化生产。     

Oviposition deterrent, ovicidal and gravid mortality effects of ethanolic extract of Andrographis paniculata Nees against the malarial vector Anopheles stephensi Liston (Diptera: Culicidae)

Oviposition is an important phenomenon of mosquitoes and has recently become the focus in the concept of integrated vector control management. In the present study, we evaluated oviposition deterrent, ovicidal and mortality effects of ethanolic extract of Andrographis paniculata Nees against gravid and oviposited females of Anopheles stephensi Liston. Water treated with the ethanolic extract had a high deterrent activity in ovipositing females: oviposition activity index values for the test species were –0.28, –0.45, –0.49 and –0.59 for extract concentrations of 29, 35, 41 and 46 p.p.m., respectively. High degrees of mortality were observed with various concentrations of extract: 1.12 (control) to 11.70 for gravid females, and 0.65 (control) to 10.25 for oviposited females. The highest mortality in both gravid and oviposited females was observed soon after they came in contact with oviposition medium treated with the extract, and this was found to be significant at doses higher than 35 p.p.m., suggesting possible contact toxicity of the extract. The extract caused moderate ovicidal activity against various age groups of A. stephensi, but it inflicted delayed effects such as high larval, pupal and adult mortality. The age of the eggs and the duration of the extract treatment influenced the ovicidal activity observed. It is clear that ethanolic extract of A. paniculata Nees can affect the oviposition cycle of A. stephensi Liston, thereby suppressing the vector population and adversely influencing transmission of the disease pathogen.     

陕西秦岭拟大萼苔科的2个新记录种

报道陕西秦岭的2个苔类新记录种:红色拟大萼苔[Cephaloziella rubella(Nees) Warnst.]和被刺拟大萼苔(Cephaloziella spinicaulis Douin.)。根据标本对2种植物的形态进行了详细的描述,同时对其地理分布进行了简要说明。     

Glycosides from Dicliptera riparia

The dimeric monoterpenoid glycoside, dicliripariside A, and two flavonoid glycosides, dicliriparisides B and C, together with six known compounds, beta-sitosterol, 2,5-dimethoxy-p-benzoquinone, vanillic acid, daucosterol, lugrandoside and poliumonside, were isolated from the aqueous ethanol extract of the whole plants of Dicliptera riparia Nees. Their structures were determined based on analyses of spectroscopic data.     

国产润楠属植物的叶表皮特征及其系统学意义

对45种国产润楠属(Machilus Nees)植物的叶表皮进行光学显微镜和扫描电镜观察,其中31种为首次报道.结果表明:润楠属植物叶表皮细胞形状为多边形或不规则形,气孔复合体均为平列型且仅分布在下表皮;上下表皮细胞的垂周壁式样有5种类型:平直、圆滑、浅波、波状、平直-弓形;下表皮毛被有(稀疏、密集或非常密集)或无;上表皮平周壁纹饰类型有:点状、平滑、条纹(或波浪条纹);下表皮内面平周壁纹饰类型有:不规则、平滑、粗糙网状、微毛状、颗粒状、鳞片状.这些特征在本属种间存在较显著的差异,可作为区分种类的辅助特征和种间亲缘关系,因而对润楠属植物的分类学研究和亲缘关系的确定有较大意义.     

人参种群2000年间向北消退的历史及其与人口压力关系的初步分析

本文通过对大量的历史资料的整理分析及人参产地的实际研究,给出了人参种群分布区在近2000多年间从黄河岸边向北消退的历史概况。就人参种群历史性消退的机理作了初步分析,建立了人参种群生存空间遭受人为破坏的生态环境模型,确定了人参种群承受人口压力阈值为45人/km~2左右.最后得出,由于人口压力的作用而迫使人参种群历史性消退的结论.