Large clones on cliff faces: expanding by rhizomes through crevices

BACKGROUND AND AIMS: Large clones of rhizomatous plants are found in many habitats, but little is known about whether such clones also occur on cliff faces where environmental conditions are extremely harsh and heterogeneous. METHODS: Using molecular (intersimple sequence repeat, ISSR) markers, the genotypic composition of a cliff-face population of Oxyria sinensis in Sichuan, China, was investigated. KEY RESULTS: The 98 O. sinensis ramets sampled belonged to 12 different genotypes (clones). The three most frequent clones were represented with 45, 22 and 12 ramets, respectively; the remaining nine were represented with only one to five ramets. The three largest clones spanned at least 2.7 m in the vertical direction and 4.6-6.9 m in the horizontal direction on the cliff face. CONCLUSIONS: On the cliff face, large clones of O. sinensis are formed by rhizomes growing along the crevices. Expansion by rhizomes may help O. sinensis to exploit the patchy resources and support establishment and growth of new ramets. Moreover, rooted ramets connected by rhizomes may effectively reduce the susceptibility of O. sinensis to rock fall and erosion and thus greatly improve the chances for long-term survival. The multi-clone structure indicates that sexual reproduction is also important for the long-term persistence of O. sinensis populations on cliffs.     

膨化饲料动植物蛋白比对中华鳖稚鳖生长特性的影响

本实验设计了营养相近、不同动植物蛋白比的四种膨化饲料（饲料1,1.5∶1;饲料2,3∶1;饲料3,5∶1;饲料4,7∶1）,研究了动植物蛋白比对中华鳖稚鳖摄食、生长、饲料利用能力和营养组成的影响。饲料1组稚鳖的摄食率显著高于饲料2—4组。饲料1—4组稚鳖的特定生长率没有显著影响。饲料1组稚鳖的干物质和脂类消化率、饲料转化效率、蛋白贮积率和能量贮积率显著低于饲料2—4组。饲料1组稚鳖体脂肪含量显著低于饲料4组。稚鳖的上述指标在饲料2—4组间均无显著差异。结果表明,鳖膨化饲料动植物蛋白比对中华鳖稚鳖生长特性有明显的影响,适宜的动植物蛋白比为3∶1。     

Effects of ammonium feeding on the production of bioactive metabolites (cordycepin and exopolysaccharides) in mycelial culture of a Cordyceps sinensis fungus

AIMS: To examine the effects of ammonium feeding on the production of cordycepin (3'-deoxyadenosine, a nucleoside analogue) and exopolysaccharides (EPS) in mycelial culture of a new Cordyceps sinensis fungus Cs-HK1. METHODS AND RESULTS: Cs-HK1 fungus was cultivated in a liquid medium containing glucose, yeast extract, peptone and a few major inorganic salts. NH(4)Cl was fed to the mycelial culture at various concentrations from 5 to 40 mmol l(-1) on day 3 (during exponential phase). NH(4)Cl, fed at 10 mmol l(-1), stimulated the cordycepin production most significantly, with nearly fourfold increase in the cordycepin content of mycelia (from 28.5 to 117 microg g(-1)), and also increased the EPS production by 40% (from 2.6 to 3.7 g l(-1)). The ammonium feeding had a slightly positive effect at 5-10 mmol l(-1), but a negative effect at higher concentrations on the mycelium growth. Ammonium feeding also caused a sharp drop of the medium pH, owing perhaps to the uptake of NH(3) and the release of H(+) by the fungal cells. CONCLUSIONS: Ammonium feeding to the mycelial culture of Cs-HK1 fungus enhanced the intracellular cordycepin accumulation and the EPS production. The enhanced cordycepin production may be attributed to the uptake of ammonia for nucleoside synthesis, and the enhanced EPS to the increased uptake of glucose for EPS biosynthesis. SIGNIFICANCE AND IMPACT OF THE STUDY: It is useful for the production of bioactive metabolites and for understanding ammonium metabolism and its relationship to the biosynthesis of nucleosides in a precious medicinal fungus.     

寄主植物对荔枝蒂蛀虫产卵的引诱作用

试验观察荔枝蒂蛀虫Conopomorpha sinensisBradley对寄主植物品种、器官及器官部位的产卵选择性规律。结果表明,与老梢相比,荔枝蒂蛀虫明显倾向于选择嫩梢产卵;4个荔枝品种果枝中以妃子笑上落卵数最多,在淮枝、糯米糍荔枝果实上较少,桂味荔枝上最少;不同的荔枝品种果实气味引诱雌虫产卵的能力不同,其中妃子笑引诱力最强,淮枝、糯米糍引诱力较低,桂味最低;在同一荔枝果实不同部位的落卵量,以果皮上、下两部分较大,全果明显低于果皮上部,而荔枝肉和荔枝核上没有落卵。     

当归根显微结构及其根腐病真菌分布研究

利用徒手切片、石蜡切片和超薄切片及显微摄像的方法,对当归根的显微结构及根腐病致病真菌的分布进行了研究。结果表明:当归的根由周皮和次生维管组织两部分组成,周皮由外向内依次分为木栓层、木栓形成层、栓内层;次生韧皮部占根径的比例在60%以上,主要成分包括筛胞、韧皮薄壁细胞、韧皮纤维和分泌道,薄壁细胞富含淀粉粒等营养物质;次生木质部由导管、木薄壁细胞和木射线组成,木质部呈多元形,木射线和韧皮射线明显。在根的周皮细胞和中柱中均有真菌分布,说明真菌由木栓层、木栓形成层、栓内层依次向里侵入到韧皮薄壁细胞,在薄壁细胞内定殖并形成菌丝结或团块状结构,进而扩展成一定的侵染区域;真菌不仅侵染周皮和韧皮部,而且还进一步侵染木质部并破坏导管。此外,研究还发现,淀粉粒是真菌定殖的主要场所,真菌穿透或缠绕在淀粉粒上,并利用其营养不断地生长与繁殖。     

中国特产2种濒危水韭雄性发育的比较研究

采用透射电镜和光镜比较观察了中华水韭和云贵水韭雄配子体及其精子的发育特征。结果显示:(1)2种水韭的雄配子体的寿命只有15~30d,终生都在小孢子壁内发育。(2)雄配子体只含有1个原叶体细胞、1个精子器壁细胞和4个精细胞,前2个细胞内含有丰富的营养物质。(3)精子由精核、微管带、鞭毛、细胞质等4部分构成。(4)中华水韭雄配子体发生率为4.5%,平均每个雄配子体产生0.46个精子,精子游动速度约53μm/s,寿命8min;云贵水韭雄配子体发生率和产精量略高于中华水韭,但精子游动速度和寿命略低于中华水韭。研究认为,中国水韭濒危的主要原因之一是雄配子体产精率低、受到生殖生态限制、水污染对精子的危害等;雄性特征表明水韭在石松类中占有较高的进化地位;结合前人的研究成果绘出了水韭雄配子体的发育模式。     

中华绒螯蟹Dmrt基因保守区段的克隆和序列分析

Dmrt基因家族是一个与性别决定和发育相关的基因家族,在不同进化类型的生物中具有相当的保守性。采用PCR技术,扩增了中华绒螯蟹Dmrt基因的DM结构域。经序列分析,获得了Dmrt基因家族的4个成员基因EsDmrt2a、EsDmrt2b、EsDmrt2c和EsDmrt5。结果表明,不同进化地位动物的Dmrt2和Dmrt2基因DM域编码序列存在高度的同源性,显示Dmrt基因在系统进化上高度保守,序列上的相似性可能暗示着它们在功能上的保守性。     

真菌侵染引发的茶树内源糖苷酶基因差异表达

通过探讨顺-3-己烯醇、芳樟醇氧化物、芳樟醇、水杨酸甲酯、香叶醇、苯甲醇和苯乙醇7种茶叶游离态香气组分和糖苷类香气前体对茶炭疽病菌、茶云纹叶枯病菌、茶轮斑病菌和茶赤叶斑病菌4种致病菌的抑制作用,以及真菌侵染引发的茶树（Camellia sinensis）内源β-樱草糖苷酶、β-木糖苷酶、β-葡萄糖苷酶I、β-葡萄糖苷酶II、β-葡萄糖基转移酶基因的表达差异,结果表明：7种游离态香气组分和糖苷类香气前体对4种致病菌均有明显的抑制作用,其中香叶醇的抑制作用最强,在浓度为0.1mg.mL-1时即对茶炭疽病菌的抑制率达到100%。实时定量PCR结果显示：真菌侵染可不同程度诱导茶树内源糖苷酶和β-葡萄糖基转移酶基因的表达上调,且上调多发生于染病初期。     

南京方山朴树种群结构与分布格局研究

采用相邻格子样方法对南京方山国家地质公园朴树种群结构和分布格局进行了研究。结果表明：（1）各样地朴树种群的年龄结构基本相似,Ⅰ、Ⅱ级幼苗普遍较少,幼苗贮备严重不足。种群个体分布多集中在Ⅲ级,Ⅳ级以上种群个体分布渐趋减少。（2）从静态生命表可以看出,由于Ⅰ、Ⅱ级幼苗、幼树数量偏少,导致种群Ⅰ、Ⅱ龄级的死亡率为负值,而Ⅶ、Ⅷ龄级的死亡率最大。部分龄级存在着不同程度的个体缺失,存活曲线呈明显下凹和断点波折,种群整体呈衰退趋势。（3）利用负二项参数（K）、扩散系数（C）、扩散型指数（I_δ）、Cassie指标（C_a）、丛生指数（I）、平均拥挤度指数（m^*）和聚块性指标（m^*/m）等参数对种群的空间格局进行了研究,表明朴树种群的空间分布格局为集群分布,但不同样地种群的集聚程度存在一定差异。     

Genetic consequence of restricted habitat and population decline in endangered Isoetes sinensis (Isoetaceae)

BACKGROUND AND AIMS: Isoetes sinensis (Isoeteaceae) is a critically endangered aquatic quillwort in eastern China. Rapid decline of extant population size and local population extinction have occurred in recent years and have raised great concerns among conservationists. METHODS: Amplified fragment length polymorphisms (AFLPs) were used to investigate the genetic variation and population structure of seven extant populations of the species. KEY RESULTS: Eight primer combinations produced a total of 343 unambiguous bands of which 210 (61.2 %) were polymorphic. Isoetes sinensis exhibited a high level of intra-population genetic diversity (H(E) = 0.118; hs = 0.147; I = 0.192; P = 35.2 %). The genetic variation within each of the populations was not positively correlated with their size, suggesting recent population decline, which is well in accordance with field data of demographic surveys. Moreover, a high degree of genetic differentiation (F(ST) = 0.535; G(ST) = 0.608; theta(B) = 0.607) was detected among populations and no correlation was found between geographical and genetic distance, suggesting that populations were in disequilibrium of migration-drift. Genetic drift played a more important role than gene flow in the current population genetic structure of I. sinensis because migration of I. sinensis is predominantly water-mediated and habitat range was highly influenced by environment changes. CONCLUSIONS: Genetic information obtained in the present study provides useful baseline data for formulating conservation strategies. Conservation management, including both reinforcement for in situ populations and ex situ conservation programmes should be carefully designed to avoid the potential risk of outbreeding depression by admixture of individuals from different regions. However, translocation within the same regional population should be considered as a measure of genetic enhancement to rehabilitate local populations. An ex situ conservation strategy for conserving all extant populations to maximize genomic representation of the species is also recommended.