UV-B辐射增强对海洋大型藻与微型藻种群生长关系的影响

选用孔石莼和青岛大扁藻为海洋大型藻和微型藻的代表,通过室内添加模拟试验研究了UV-B辐射增强对孔石莼(重量固定)与青岛大扁藻(密度不同)种群生长关系的影响。结果表明:(1)在单养情况下,4个UV-B辐射剂量都对孔石莼的生长产生抑制作用;对青岛大扁藻生长的影响却不同,低剂量(U-1)的UV-B辐射对青岛大扁藻的生长有促进作用,而高剂量的UV-B辐射则有显著的抑制作用;且因初始接种密度不同而各异。(2)在共养情况下,微藻对孔石莼的生长表现出一定的抑制作用,随着微藻初始接种密度的增加,其抑制作用亦增加;反之,在共培养的初始阶段(6 d内)孔石莼对微藻的生长也有抑制作用,但后期阶段(9 d后)表现出促进作用。(3)在共培养的同时附加UV-B辐射处理,随着初始接种密度的增加,青岛大扁藻对孔石莼生长的抑制作用更加明显;同时,与共养相比较,孔石莼对微藻生长的抑制作用亦趋于明显。     

4种药用芦荟叶的形态解剖学研究

通过植物形态解剖学方法研究４种药用芦蔡的叶的结构,结果表明：它们都具有早生多浆植物中的结构特征。表皮及角质层厚,气孔下陷,气孔下陷,孔下室大。叶肉分为二部分,由同化薄壁组织和储水组织组成。同化薄组织由多层细胞组成,细胞形态相似,不分化为栅栏组织和海绵组织。储水组织占据叶的体积一半以上,细胞大、不规则、壁薄、富含粘液。维管束具鞘,呈环状分布。紧靠同化组织的维管束赶忙皮薄壁组织发达,具有合成和储存芦荟     

广西岩溶区烟草黑胫病拮抗细菌的筛选鉴定及其抗病机理

从广西岩溶区靖西县优质烟叶生产区分离烟草黑胫病病原及土壤细菌,通过拮抗试验、离体及田间抗病能力测试等方法筛选拮抗细菌;利用形态观察、生理生化测试和16SrDNA序列分析三种方法相结合,对抗病效果良好的菌株进行分类鉴定;并对拮抗菌抗黑胫病机理进行初步研究。结果表明:从8份土壤样品中,共分离出土壤细菌340株,获得抗黑胫病效果良好的拮抗细菌3株,编号为8-23、6-70和13,它们分别属芽孢杆菌属、溶菌杆属和假单胞杆菌属细菌;三个拮抗细菌的抗黑胫病机理是通过胞外分泌一些可溶解病原菌细胞壁的酶或其它化学物质,破坏菌丝的细胞壁和细胞膜等生理结构,使细胞质渗漏、凝集,从而导致病原死亡;其中,菌株8-23和13的抗病活性物质主要为蛋白质类化合物;而菌株6-70除蛋白质外,还有其它一些非蛋白因子起作用。     

濒危植物太白红杉种群年龄结构及其时间序列预测分析

为了阐明太白红杉(Larix potaninii var.chinensis)种群的年龄结构和未来发展趋势,合理保护现有资源,在太白山地区调查了 29个样地(10 m×10m),对处于不同生境的 5个种群的年龄结构、静态生命表和时间序列预测进行了分析。种群年龄结构分析表明,各种群个体数量主要集中于Ⅲ、Ⅳ、Ⅴ、Ⅵ、Ⅶ龄级(个体数量比重占68.64％),幼、老龄个体数量较少。受所处生境条件影响,不同种群年龄结构特点不同:海拔较低的种群(B)由于水热条件适宜,林内有林窗出现,幼龄级个体数相对丰富;而其他种群由于幼龄个体严重缺乏,衰退趋势明显。太白红杉不同种群生命表和存活曲线的分析表明,尽管所处的生境差异较大,但存活曲线基本属于Deevey Ⅲ型,种群偏离典型存活曲线的程度与幼苗缺乏程度有关,一般V-Ⅸ龄级死亡率较高。时间序列分析表明,在未来20、60、100和200年中,各太白红杉种群均会呈现老龄级株数先增加后减少的趋势,种群稳定性维持困难。太白红杉种群年龄结构和动态趋势与银杉(Cathaya argyrophylla)等其他濒危植物比较,导致种群衰退的原因相似:在郁闭的林下种子萌芽和幼苗生长困难。应该利用太白红杉喜光、耐旱和中老年个体产种量丰富的特性,对现有太白红杉林分实行就地保护,合理抚育管理。低海拔地区,应适当间伐非目的树种     

北极岛衣共生菌藻宏基因组文库的构建

为从地衣中筛选耐寒基因,采用CTAB法提取岛衣北极变种的共生菌藻中基因组DNA,经Sau3AⅠ酶切,获得2~6 kb的DNA片段。再与经BamHⅠ酶切消化并经去磷酸化处理的质粒载体pUC19体外连接,转化至DH5α大肠杆菌(Escherichia coli)的感受态细胞中,成功构建了岛衣北极变种的宏基因组文库。     

Effects of Fragmentation of Evergreen Broad-leaved Forests on Genetic Diversity of Ardisia Crenata var. Bicolor (Myrsinaceae)

Due to the long generation times and high densities, dominant tree species usually did not respond consistently with theoretical predictions to the recent fragmentation. Genetic structures of shrubs and herbs, especially those with low densities, may be more sensitive to forest fragmentation. We studied the genetic structure of a self-compatible subshrub, Ardisia crenata var. bicolor (Myrsinaceae) in a recently fragmented landscape. Ten RAPD primers used for analysis generated a total of 76 bands. We found that A. c. var. bicolor had relatively low species-level (P₉₅ = 63.2%; H = 0.106; Shannon diversity index (SI) = 0.246) and within-population diversity (P₉₅ = 5.3−46.1%; H = 0.026−0.175; SI = 0.032−0.253), and significant population differentiation (G_ST = 0.445). Significantly positive relationships were found between measures of diversity (P₉₅, H and SI) and the log of estimated population size. No significant relationship was observed between Nei's genetic distance and spatial distance of pairwise populations, indicating no isolation-by-distance. Given most species of forests are shrubs and herbs with short generation times, our observation indicated that distinct genetic consequences of recent fragmentation may be expected for quite a number of plant species.     

Fruit photosynthesis

Abstract. In addition to photosynthesis as in the leaf, fruit possess a system which refixes CO₂ from the mitochondrial respiration of predominantly imported carbon. This pathway produces malate by the action of phosphoenolpyruvate carboxylase, PEPC, (E.C. 4.1.1.31) and appears to be regulated primarily by the cytosolic concentration of HCO₃/CO₂ and malate. Malate is stored in the vacuole as malic acid, constituting a major carbon pool and a potential substrate for respiration. The PEPC in apple fruit proves to be an efficient form of the enzyme with low Michaelis constants, i.e. Km = 0.09 mol m^-3 PEP and 0.2 mol m^–3 HCO₃, and large Ki= 110 mol m^-3 HCO³. In fleshy fruit, chlorophyll and chloroplasts are unevenly distributed; they resemble the C₃ sun-type and arc concentrated in the perivascular tissue, with smaller chloroplasts, fewer grana per chloroplast and a larger degree of vacuolation than commonly found in a leaf of the same species. Fruit photosynthesis often compensates for respiratory CO₂ loss in the light. However, due to respiration in the dark, CO₂ loss is in excess of photosynthetic gain in the light, such that a continual loss of CO₂ was observed in the diurnal cycle and which is maintained throughout fruit development. The rate of CO₂ exchange decreases on a fresh weight or surface basis, but increases with fruit ontogeny on a per fruit basis, causing accumulation of several percent CO₂ in the internal cavity. Stomata are present in the outer epidermis of those fruits examined, but with a 10-to 100-fold lesser frequency than in the abaxial epidermis of leaf of the same species. The number of Stomata is set at anthesis and remained constant, while the stomatal frequency decreases as the fruit surface expands. Stomata are as sensitive as in leaves in the early stages of fruit development, but often are transformed into lenticels during fruit ontogeny, thereby decreasing the permeability of the outer epidermis. The discrepancy between the CO₂-concentrating mechanism provided by PEPC analogous to C₄/CAM Photosynthesis and the kinetics of fruit PEPC, characteristic of C₃/non-autotrophic tissue, suggests the definition of a new type of ‘fruit photosynthesis’ rather than its categorization within an existing type.     

Bafoudiosbulbins F and G, further clerodane diterpenoids from Dioscorea bulbifera L. var sativa and revised structure of Bafoudiosbulbin B

From the bulbils of Dioscorea bulbifera L. var sativa, two clerodane diterpenoids, Bafoudiosbulbins F (1) and G (2), together with five known compounds: Bafoudiosbulbins A-C, 3,5,4'-trihydroxy-3'-methoxybibenzyl, and kaempferol were isolated. Their structures were established by spectroscopic techniques, including (1)H, (13)C NMR, NOESY, ROESY, COSY, TOCSY, HSQC, and HMBC. The relative stereochemistry of compounds 1 and 2 was assigned on the basis of X-ray crystallographic diffraction analysis. Furthermore, the structure of Bafoudiosbulbin B was revised using extensive 2D NMR techniques as well as chemical transformation.     

北京山区侧柏-荆条系统水分来源对降雨事件的响应

分析了北京鹫峰山区侧柏、荆条枝条水及其潜在水分来源的氢氧同位素特征,运用IsoSource模型解析侧柏、荆条系统水分利用来源的季节变化及其对降雨事件的响应.结果表明:旱季初期(4月)研究区0～20 cm土层富集土壤水¹⁸O值,20 cm以下该值则随着土层深度增加逐渐减小,侧柏主要利用前2～3 d降雨补充的0～30 cm层土壤水;旱季末期(6月)侧柏和荆条分别利用当天雨水补充的0～10和10～30 cm层土壤水;雨季(7月)侧柏利用前期降水补给的0～40 cm层土壤水(59.3%)和近期降水(12.5%),荆条则利用近期降雨供给的0～30 cm层土壤水;侧柏的土壤水分来源逐月加深,至生长季末(11月)其主要利用60～80 cm层土壤水(前2～3 d降雨补给),而荆条枝条水δ¹⁸O值远离各水分来源δ¹⁸O值.两物种对水分的竞争压力小,适应本区域气候特征,尤其在应对特大暴雨等极端天气时,植物系统垂直分布的水分来源能够有效分流洪峰,减小暴雨瞬时破坏力.     

单面针的生物碱研究

自芸香科(Rutaceae)花椒属植物单面针(Zanthoxylum nitidum var. fastuosum How ex Huang)的根皮中分得五种已知生物碱:乙氧基白屈菜红碱(ethoxychelerythrine)(Ⅰ);氯化光花椒碱(nitidine chloride)(Ⅱ);去甲基白屈菜红碱(des-N-methychelerythrine)(Ⅲ);α—别隐品碱(α-allocryptopine)(Ⅳ);鹅掌揪宁(liriodenine)(Ⅴ).