Nitrogen nutrition and water stress effects on leaf photosynthetic gas exchange and water use efficiency in winter wheat

The responses of gas exchange and water use efficiency to nitrogen nutrition for winter wheat were investigated under well-watered and drought conditions. The photosynthetic gas exchange parameters of winter wheat are remarkably improved by water and nitrogen nutrition and the regulative capability of nitrogen nutrition is influenced by water status. The effects of nitrogen nutrition on photosynthetic characteristics and on the limited factors to photosynthesis are not identical under different water status. Intrinsic water use efficiency (WUE(i)) of the plants at the high-N nutrition was decreased by a larger value than that of the plants in the low-N treatment due to a larger decrease in photosynthetic rate than in transpiration rate. Carbon isotope composition of plant material (delta(p)) is increased by the increase of drought intensity. The delta(p) at a given level of C(i)/C(a) is reduced by nitrogen deficiency. Leaf carbon isotope discrimination (Delta) is increased by the increase of nitrogen nutrition and decreased by the increase of drought intensity. Transpirational water use efficiency (WUE(t)) is negatively correlated with Delta in both nitrogen supply treatments and increased with the nitrogen supply.     

山西关帝山种子植物区系研究

关帝山位于吕梁山脉中部,有种子植物７３７种,属于３３５属、８５科。种子植物属种区系成分复杂多样,以温带尬发占绝对优势（温带属２４９属,占总属数的８５．６７％）。对属种区系成分和植被建群种和优势种组成的分析表明,关帝山具有典型的明温带落叶阔叶林性质。与有关山地植物区系与植被组成的比较,关帝山与太岳山具有较高的同质性和密切的联系,与太行山南部次之,而与秦岭太白山具有明显的差异。     

葡萄SBP基因家族生物信息学分析

SBP(squamosa promoter binding protein,SBP)基因家族是植物所特有的一类重要转录因子,广泛参与植物生长、发育以及多种生理生化反应的信号传导。葡萄是继拟南芥、水稻和杨树之后完成全基因组测序的第四种开花植物,因此葡萄逐渐成为分子生物学研究的重点对象,进行葡萄基因组信息挖掘与分析对于葡萄功能基因组学的发展具有重要意义。本文利用生物信息学方法对葡萄家族45条SBP蛋白序列的系统发生和SBP基因组定位进行分析,然后对其氨基酸组成成分、理化性质以及二级和三级结构进行预测和分析,同时还分析了葡萄与拟南芥的SBP基因家族之间的联系。结果显示这45条蛋白序列与拟南芥16个SBP基因蛋白序列一起分成了3个亚族,说明拟南芥与葡萄SBP基因间具有较高的保守性;进一步的基因组定位结果发现其分布在14条染色体上,较拟南芥在染色体上的分布更为分散。研究还发现不同亚家族间氨基酸数目、氨基酸序列间的疏水性存在一定的差异;而二级结构预测结果发现,41条氨基酸序列以随机卷曲为主要组成部分,这与拟南芥相似,且45条氨基酸序列三维结构十分相似。本文实验结果均为葡萄SBP基因家族的进一步功能分析提供了重要研究基础。     

Foliar δ<Superscript>13</Superscript>C values of nine dominant species in the Loess Plateau of China

The foliar stable carbon isotope compositions (δ¹³C) of nine dominant species in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi, and Shenmu, standing from the south to the north in the Loess Plateau of China were studied. The results showed that foliar δ¹³C values ranged from −22.61 to −30.73 ‰ with an average of −27.23 ‰ in 141 C₃ plant samples collected from the Loess Plateau. Foliar δ¹³C values varied significantly (p<0.001) among the nine C₃ species, which were Pinus tabulaeformis Carr., Robinia pseudoacacia L., Zizyphus jujuba Mill. var. spinosus Hu., Rubus parvifolius L., Hippophae rhamnoides L., Caragana korshinskii Kom., Lespedeza davurica (Laxm.) Schindl., Artemisia sacrorum Ledeb. var. incana Mattf., and Agropyron cristatum Gaertn. Comparatively, R. pseudoacacia, H. rhamnoides, and C. korshinskii had much higher δ¹³C values than the other six species, while A. sacrorum had the lowest δ¹³C value. There was no significant difference in foliar δ¹³C value among five species, P. tabulaeformis, Z. jujuba, R. parvifolius, L. davurica, and A. cristatum. Considering the life forms categorized from nine C₃ species, trees and shrubs had significantly higher δ¹³C values than herbs (p<0.001). The deciduous tree R. pseudoacacia had much higher δ¹³C value than the evergreen tree P. tabulaeformis (p<0.01). Among the four shrubs, foliar δ¹³C values in H. rhamnoides and C. korshinskii were markedly higher (p<0.01) than those in Z. jujuba and R. parvifolius. Among the three herbs, L. davurica and A. cristatum had significantly higher δ¹³C values than A. sacrorum (p<0.01). Leguminous species such as R. pseudoacacia, C. korshinskii, and L. davurica as well as a non-leguminous species with nitrogen-fixation capacity, H. rhamnoides, had higher δ¹³C values than other non-leguminous species with same life-form. The mean δ¹³C value increased by about 7 % from Yangling in the south to Shenmu in the north as climatic drought increased, and foliar δ¹³C values differed much (p<0.001) among the seven sites. For nine species in the Loess Plateau, foliar δ¹³C values were significantly and negatively (p<0.001) correlated with the mean annual precipitation, moreover, an increase of 100 mm in annual precipitation would result in a decrease of 1.2 ‰ in δ¹³C value.     

A novel matrix for high performance affinity chromatography and its application in the purification of antithrombin III

Viscose fiber, a regenerated cellulose, was evaluated for using as a novel matrix for high performance affinity chromatography. With a one-step activation with epichlorohydrin, heparin can be readily covalently attached to the matrix. This heparin-viscose fiber material was used for purifying antithrombin III (AT III) from human plasma. The purity of the AT III from this one-step purification is 93% as measured by SDS-PAGE and the protein recovery yield is about 90%. This column is highly specific as described by the dissociation constant of the complex of immobilized heparin and AT III, which was 2.83 x 10(-5)mol/L. And more important, this viscose fiber material demonstrated its excellent mechanical property that allows the flow rate to reach up to 900 cm/h or more.     

Formation of homogeneous unilamellar liposomes from an interdigitated matrix

Phospholipid-ethanol-aqueous mixtures containing bilayer-forming lipids and 20-50 wt.% of water form viscous gels. Further hydration of these gels results in the formation of liposomes whose morphology depends upon the lipid type. Upon hydration of gels containing mixtures of the lipids 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), small homogeneous and unilamellar liposomes were produced. In contrast, hydration of gels containing only POPC resulted in formation of large multilamellar liposomes. Likewise, mulitlamellar liposomes resulted when this method was applied to form highly fusogenic liposomes comprised of the novel negatively charged N-acyl-phosphatidylethanolamine (NAPE) mixed with di-oleoyl-phosphatidylcholine (DOPC) (7:3) [T. Shangguan, C.C. Pak, S. Ali, A.S. Janoff, P. Meers, Cation-dependent fusogenicity of an N-acyl phosphatidylethanolamine, Biochim. Biophys. Acta 1368 (1998) 171-183]. In all cases, the measured aqueous entrapment efficiencies were relatively high. To better understand how the molecular organization of these various gels affects liposome morphology, we examined samples by freeze-fracture transmission electron microscopy and X-ray diffraction. We found that phospholipid-ethanol-water gels are comprised of highly organized stacks of lamellae. A distinct feature of the gel samples that result in small unilamellar liposomes is the combination of acyl chain interdigitation and net electrostatic charge. We speculate that the mechanism of unilamellar liposome formation proceeds via formation of stalk contacts between neighboring layers similar to membrane hemifusion intermediates, and the high aqueous entrapment efficiencies make this liposome formation process attractive for use in drug delivery applications.     

Relationship between δ13C and photosynthetic parameters and their responses to leaf nitrogen content in six broadleaf tree species

Stable carbon isotope composition (δ¹³C), net photosynthetic rate (P _N), actual quantum yield of photosystem 2 (PS2) electron transport (ΦPS2), nitrogen content (N_c), and photosynthetic nitrogen use efficiency (PNUE) in the leaves of six broadleaf tree species were determined under field environmental conditions. The six tree species were Magnolia liliflora Desr., M. grandiflora Linn., M. denudata Desr., Prunus mume (Sieb.) Sieb. et Zucc. cv. Meiren Men, P. mume (Sieb.) Sieb. et Zucc. f. alphandii (Carr.) Rehd., and P. persica (L.) Batsch. var. rubro-plena. The relationships among δ¹³C, Φ_PS2, P _N, and PNUE, as well as their responses to N_c in the six species were also studied. Both P _N and δ¹³C negatively correlated with N_c, but Φ_PS2 positively correlated with N_c. This indicated that with N_c increase, P _N and δ¹³C decreased, while Φ_PS2 increased. There were weak negative correlations between δ¹³C and PNUE, and strong negative correlations (p<0.01) between Φ_PS2 and PNUE. According to the variance analysis of parameters, there existed significant interspecific differences (p<0.001) of δ¹³C, P _N, Φ_PS2, PNUE, and N_c among the tree seedlings of the six tree species, which suggests that the potential photosynthetic capacities depend on plant species, irradiance, and water use capacity under field conditions.     

Improved synthesis of 2′-deoxyadenosine and 5-methyluridine by Escherichia coli using an auto-induction system

Nucleoside analogues are used widely for the treatment of viral diseases and cancer, however the preparation of some important intermediates of these nucleoside analogues, including 2′-deoxyadenosine (dAR) and 5-methyluridine (5-MU), remains inconvenient. To optimize the synthesis of dAR and 5-MU, recombinant strains and auto-induction medium were employed in this study. E. coli BL21(DE3) strains overexpressing purine nucleoside phosphorylase (PNP), uridine phosphorylase (UP) and thymidine phosphorylase (TP) were constructed and cultured in auto-induction ZYM-Fe-5052 medium for 8 h. The cultures of these strains were then used directly to synthesize dAR and 5-MU. Under optimized conditions, 30 mM adenine was converted to 29 mM dAR in 1 h, and 32 mM 5-MU was obtained from 60 mM thymine, using 6% (v/v) cell solutions as biocatalysts. These results indicate that our convenient and efficient method is ideal for the preparation of dAR and 5-MU, and has potential for the preparation of other nucleoside analogue intermediates.     

晋、陕、宁、蒙柠条锦鸡儿群落物种多样性对放牧干扰和气象因子的响应

根据晋、陕、宁、蒙地区13个样地的野外调查资料,采用丰富度指数、物种多样性指数以及均匀度指数,研究了柠条锦鸡儿群落物种多样性对放牧干扰和气象因子的响应。结果表明：（1）晋、陕、宁、蒙地区柠条锦鸡儿群落组成成分简单,共记录种子植物111种,分属25科,64属,灌木层优势种为柠条锦鸡儿,草本层优势种集中于禾本科、豆科、菊科蒿属和藜科;（2）受人为干扰、土壤和气候等影响,群落的组成、结构及其综合性质具有一定差异性,主要表现在群落的Patrick指数与Simpson指数、Shannon-wiener指数出现较大的波动,且波动趋势基本一致,Pielou指数表现较为稳定;（3）放牧干扰强度与群落Simpson指数、Shannon-wiener指数呈极显著相关（P＜0.01）,与Patrick指数、Pielou指数呈显著相关（P＜0.05）,群落丰富度随放牧干扰强度的增大而下降,群落多样性和均匀度指数在D2和D3时呈现峰值,表明适度干扰可以提高群落物种多样性和均匀度;（4）Patrick指数、Simpson指数和Shannon-wiener指数均与年均降水量呈极显著正相关(P＜0.01),与相对湿度呈显著正相关（P＜0.05）,共同体现了水分条件是制约柠条锦鸡儿群落物种多样性的决定性因子。