Hydraulic Conductance and Stomatal Sensitivity to Changes of Leaf Water Status in Six Deciduous Tree Species

The relationship between shoot hydraulic conductance (L) and stomatal sensitivity to changes in leaf water status was studied in the saplings of six deciduous tree species. L increased significantly in sequence: Acer platanoides < Tilia Cordata < Padus avium = Quercus robur < Salix caprea = Populus tremula. L was higher in the trees grown in soil with a higher nitrogen content and lower in the trees grown under mild water stress or kept in darkness for several days. L was higher in July than in September in all the species. L correlated positively with maximum photosynthesis, stomatal conductance and stomatal sensitivity to an increase in leaf water potential, but negatively with stomatal sensitivity to a decrease in leaf water potential. The correlations between L and any other parameter were approximated by three different curves: data for water-stressed plants fit to the first, data for plants kept in darkness fit to the second and all the other data fit to the third curve. The reasons of the differences of shoot hydraulic conductance in the different experimental sets and the mechanisms which may cause the correlation between L and the other characteristics are discussed.     

中国科学家完成博落回全基因组测序并解析苄基异奎宁类生物碱途径

博落回(Macleaya cordata)是罂粟属的一种传统中药, 因其富含具有抗菌功能的血根碱(SAN)和白屈菜红碱(CHE), 可以作为牲畜抗菌生长促进剂的安全来源植物。中国科学家以博落回为材料, 利用从头测序手段测定了首个罂粟属植物全基因组序列。研究人员通过组织特异性代谢谱及表达谱分析鉴定了博落回中16个参与血根碱和白屈菜红碱合成的候选基因, 并结合同源克隆及饲喂实验对其中的14个基因进行了体外功能验证。上述研究为进一步探索博落回中血根碱等苄基异奎宁类生物碱(BIAs)合成、调控及后续合成奠定了基础, 也为解析罂粟属其它植物的代谢途径提供了有力工具。     

Differential diversifications of South American and Eastern Asian disjunct genera Bocconia and Macleaya (Papaveraceae)

Bocconia (10 species) and Macleaya (2 species) are two disjunct genera between South America and eastern Asia (EAS) in the Papaveraceae offering an opportunity to compare its biogeographic history with that of the well‐known disjunction between EAS and eastern North American (ENA). Our phylogenetic analyses of the chloroplast matK and rbcL gene sequences of Ranunculales including two species of Macleaya and six species of Bocconia supported the monophyly of Bocconia, Macleaya, and Chelidonioideae to which Bocconia and Macleaya belong. Nucleotide sequences of matK, rbcL, and nrDNA ITS supported the sister relationship of Bocconia and Macleaya. Biogeographic analyses of Chelidonioideae using S‐DIVA (statistical dispersal vicariance analysis) and DEC (dispersal extinction cladogenesis) methods inferred Eurasia as the most likely ancestral area of Bocconia and Macleaya and suggested no extinction events in either Bocconia or Macleaya. This agrees with the “Out‐of‐Asia” pattern of the EAS‐ENA disjunction. Molecular dating of Ranunculales with fossil‐based calibrations showed that Bocconia and Macleaya diverged in the late Eocene and early Oligocene, which is much earlier than most EAS‐ENA disjunct taxa. The disjunction may have formed via long distance dispersal or boreotropical connections via the North Atlantic and Bering land bridges. Both Bocconia and Macleaya diversified in the late mid‐Miocene, but Bocconia has apparently experienced a greater diversification probably aided by the evolution of the bird dispersal syndrome in fruit and seed after migration to South America. The greater diversification of Bocconia is also evidenced by the diverse leaf morphology and growth habit in response to colonization in various local habitats in South America.     

Danish deciduous forest types

In this study, the first comprehensive multivariate statistical analysis of Danish native forest vegetation, based on 1768 sample plots, is presented. Data were composed of data from literature sources and newly collected data. A series of cluster analyses resulted in 24 forest community types, grouped in beech (Fagus sylvatica), oak (Quercus robur-Q. petraea), hornbeam (Carpinus betulus), alder-ash (Alnus-Fraxinus) and lime (Tilia cordata, T. platyphyllos) types, in addition to mixed forest communities with several co-dominant tree species. The described communities are provisionally arranged syntaxonomically, when possible, according to the international phytosociological system. The distribution of ecological indicator values of pH, soil moisture and nitrogen is gradual in relation to the perceived plant communities. Many forest types, such as beech and oak dominated types, obtain indicated values for pH that span most of the indicated gradient. It is suggested that natural Danish forests probably would be composed of a multitude of canopy forming tree species. The present stands with one or a few tree species forming the canopy is the result of long anthropogenic influence and selective logging.     

The macrophytobenthos of Terra Nova Bay (Ross Sea,Antarctica): results of three Italian scientific expeditions

Abstract

The results of a study on the benthic macroalgal flora and vegetation of Terra Nova Bay (Ross Sea) carried out during the Italian expeditions to Antarctica made in the years 1987/88, 1989/90 and 1993/94, are presented. The flora is rather poor (9 Rhodophyceae, 4 Fucophyceae, 4 Chlorophyceae), but richer than that known from adjacent areas. The vegetation is on the whole characterized by a prevalence of sciaphilous species among which Iridaea cordata, Phyllophora antarctica and Clathromorphum lemoineanum dominating in the upper infralittoral, lower infralittoral and circalittoral zones, respectively. Moreover, the results of a study on biomass of a population of I. cordata as well as of a population of P. antarctica, carried out in the austral summer 1993/94, are reported too. The values of the biomass of the population of I. cordata resulted to vary inversely with respect to those of the population of P. antarctica.     

LIFE HISTORY VARIATIONS IN A PREDOMINANTLY GAMETOPHYTIC POPULATION OV IRIDAEA CORDATA (GIGARTINACEAE, RHODOPHYTA)1

An Iridaea cordata ( Turner) Bory population made up of 83% gametophytes and 17% tetrasporophytes demonstrated little variation in these proportions over three years. These data contrast with an expectation that alternations of generations, as demonstrated by culture studies, should result in equal numbers of isomorphic generations. Analyses of reproductive and demographic attributes of the population were made to better understand the role of alternation of generations in this population .
Growth and mortality rates in the summer could not account for the success of gametophytes. however, size class frequencies demonstrated that tetrasporophytes were smaller individuals. Sporelings recruited into this intertidal region and made up 20% of the spring population numbers. Even with this level of recruitment, gametophyte-to-tetrasporophyte ratios did not change. Perennating holdfasts regenerated 80% of the spring number and 90% of the total blade area. Consequently, perennation and differential survival of gametophyte spores or sporelings are proposed as mechanisms maintaining gatnetophyte dominance in this San Juan Island, Washington population .     

成都平原不同种植方式折耳根表面附生细菌群落结构与抗生素抗性基因分析

【目的】分析有机、化肥和野生折耳根表面的附生细菌群落结构和抗生素抗性基因(ARGs),揭示细菌群落结构与ARGs相互关系。【方法】高通量测定16SrRNAV3-V4可变区序列分析样品表面附生细菌群落结构;PCR和qPCR扩增29种ARGs基因分析样品表面ARGs污染情况;冗余分析(RDA)探讨细菌群落结构与ARGs的相互关系。【结果】折耳根表面检测到35个属的细菌,其中有机折耳根表面附生细菌多样性低于化肥和野生折耳根(P0.05);29种被检的ARGs中,有14种在折耳根中被检出,其中有机折耳根含有全部被检出的ARGs,化肥和野生折耳根则含有部分被检出的ARGs。折耳根表面ARGs污染的多样性和丰度显著受到样品表面的菌群结构影响,其中Lactococcus、 Escherichia、Fluviicola、Enterococcus、Sanguibacter和Acidovorax是影响ARGs最主要的菌群。【结论】有机种植极大地改变了折耳根表面附生细菌的群落结构,增加了ARGs的多样性和丰度,对有机折耳根的食品安全带来了潜在威胁。因此,有必要将ARGs污染监测纳入到有机折耳根的食品安全考核范围内。     

博落回提取物替代抗生素对肉鸡生长性能、盲肠微生物及盲肠紧密连接的影响

【目的】本研究旨在探讨博落回提取物(Macleayacordataextract,MCE)替代促生长抗生素(Antibiotic growth promoters,AGPs)对黄羽肉鸡生长性能、盲肠微生物及紧密连接mRNA表达的影响。【方法】试验选取体重相近、体型均匀、健康状况良好的1日龄温氏新黄鸡二号公鸡300只,随机分为5组,每组6个重复,每个重复10羽。分别饲喂基础日粮(NC)、抗生素日粮(ANT,基础日粮添加50 mg/kg那西肽和50 mg/kg金霉素)和试验日粮(基础日粮中添加200、400、800 mg/kg MCE),试验期60 d。【结果】日粮添加400 mg/kg MCE替代AGPs显著降低了料肉比(P0.05),并显著增加了盲肠长度(P0.05)。日粮添加MCE显著提高了肉鸡盲肠食糜中Firmicutes细菌数量和ClostridiumclusterXIVa数量(P0.05);MCE替代AGPs显著降低了盲肠Escherichia coli数量(P0.05)。400 mg/kg和800 mg/kg MCE替代日粮中AGPs显著增加了肉鸡盲肠食糜中总短链脂肪酸、乙酸和丁酸含量(P0.05);400 mg/kg MCE替代AGPs显著提高了盲肠中支链脂肪酸异丁酸和异戊酸的浓度(P0.05)。日粮添加MCE显著上调了肉鸡盲肠Claudin-1、JAM2、ZO-1的mRNA表达量(P0.05),并降低了黏蛋白MUC2、MUC5ac和MUC13的表达量(P0.05)。【结论】MCE替代AGPs可通过提高盲肠有益菌数量和短链脂肪酸浓度,促进肠道发育,提升肠道屏障功能等途径,改善黄羽肉鸡生长性能,本研究中其最适添加量为400 mg/kg。     

鱼腥草褐斑病的病原及其生物学特性

在贵州省施秉县鱼腥草上发生一种新的叶斑类病害,有危害加重趋势。为明确该病的病原菌,本研究采用组织分离法和离体接种法进行了病原菌分离培养和致病性测定,通过形态特征观察及rDNA ITS和Tef1两个核苷酸片段序列分析,将该病菌鉴定为拟盘多毛孢Pestalotiopsis sp.,系鱼腥草上首次报告。对该病原菌的生物学特性进行了研究。发现葡萄糖和蛋白胨最适于该菌菌丝体生长,菌丝体最适生长温度为25℃,最适宜pH 8,病菌在玉米粉培养基上生长最快,光照有利于菌丝体生长。