内蒙古欧李果肉和果仁中营养成分分析

对内蒙古欧李果肉及果仁中营养成分进行研究,结果表明,欧李中维生素、矿物质、蛋白质等营养成分丰富,其中VC的质量分数为590.1 mg.kg-1,远远高于苹果、草莓、葡萄、柑橘、西红柿等水果的VC含量;矿物质元素Ca质量分数在果肉中达428.1 mg.kg-1,是其它水果Ca含量的2~10倍;果仁中达3.743 g.kg-1,其含量与杏仁中相当;蛋白质含量丰富,氨基酸种类齐全,必需氨基酸在果肉和果仁中所占比例达氨基酸总量的1/3以上,为以后的研究开发利用提供了理论依据。     

Plant-microbe competition for soil amino acids in the alpine tundra: effects of freeze-thaw and dry-rewet events

Amino acids have been shown to be a potentially significant N source for the alpine sedge, Kobresia myosuroides. We hypothesised that freeze-thaw and dry-rewet events allow this plant species increased access to amino acids by disrupting microbial cells, which decreases the size of competing microbial populations, but increases soil amino acid concentrations. To test this hypothesis, we characterized freeze-thaw and dry-rewet events in the field and simulated them in laboratory experiments on plant-soil microcosms. In one experiment, ¹⁵N,¹³C-[2]-glycine was added to microcosms that had previously been subjected to a freeze-thaw or dry-rewet event, and isotopic concentrations in the plant and microbial fractions were compared to non-stressed controls. Microbial biomass and uptake of the labeled glycine were unaffected by the freezing and drying treatments, but microbial uptake of ¹⁵N was lower in the two warmer treatments (dry-rewet and summer control) then in the two colder treatments (freeze-thaw and fall control). Plant uptake of glycine-¹⁵N was decreased by climatic disturbance, and uptake in plants that had been frozen appeared to be dependent on the severity of the freeze. The fact that intact glycine was absorbed by the plants was confirmed by near equal enrichment of plant tissues in ¹³C and ¹⁵N. Plants under optimal conditions recovered 3.5% of the added ¹⁵N and microbes recovered 5.0%. The majority of the ¹³C and ¹⁵N label remained in a non-extractable fraction in the bulk soil. To better understand the isolated influences of environmental perturbations on soil amino acid pools and population sizes of amino-acid utilizing microbes, separate experiments were performed in which soils, alone, were subjected to drying and rewetting or freezing and thawing. Potential respiration of glycine and glutamate (substrate-induced respiration; SIR) by the soil microbial communities was unaffected by a single freeze-thaw event. Glycine SIR was decreased slightly (∼10%) by the most extreme drying treatment, but glutamate SIR was not significantly affected. Freezing lowered the concentration of water-extractable amino acids while drying increased their concentration. We interpret the surprising former result as either a decrease in proteolytic activity in frozen soils relative to amino acid uptake, or a stimulation in microbial uptake by physical nutrient release from the soil. We conclude that climatic disturbance does not provide opportunities for increased amino acid uptake by K. myosuroides, but that this plant competes well for amino acid N under non-stressed conditions, especially when soils are warm. We also note that this alpine tundra microbial community's high resistance to freeze-thaw and dry-rewet events is novel and contrasts with studies in other ecosystems. Received: 24 February 1997 / Accepted: 28 August 1997     

Ectomycorrhizal transfer of amino acid-nitrogen to the alpine sedge Kobresia myosuroides

Previous work in the Colorado alpine ecosystem has shown that amino acids are a potentially important N source for the sedge, Kobresia myosuroides . This plant is the only known sedge to harbour associations with ectomycorrhizal fungi. The aim of the present work was to test the hypothesis that these ectomycorrhizas transfer N from amino acids in the soil solution to the host plant, and thereby have an important role in the N nutrition of this species. We used a two-chamber system (rhizoboxes) in which K. myosuroides plants were separated from a soil chamber by nylon mesh that allowed fungal hyphae, but not plant roots, to cross it. Injections of [¹⁵N, 2-¹³C]glycine were made into the soil chamber. The hyphal crossings on half of the rhizoboxes were regularly disrupted to control for leakage of label across the barrier. Plants in the intact rhizoboxes showed significantly higher ¹⁵N enrichment than those in controls, and mycorrhizal root tips were significantly more enriched than bulk roots. The mycorrhizas transferred an average of 1.3% of the added ¹⁵N label to plants, a figure comparable to those obtained in previous studies in which plant roots were directly exposed to label. We conclude that fungal associations have an important role in the N nutrition of K. myosuroides by transferring N from amino acids to their hosts.     

嵩草属植物的胚胎学

对嵩草属（ Ｋｏｂｒｅｓｉａ） 植物进行了初步的胚胎学研究。该属植物具假四合花粉（ｐｓｅｕｄｏｍｏｎａｄ） ; 药室内壁在二核花粉时期开始螺旋状加厚, 花药表皮在花粉成熟时形成乳突; 成熟花粉具三细胞。胚珠为倒生型, 具厚珠心和双层珠被, 珠孔由内珠被构成, 珠柄的近基部向珠孔增生形成珠孔塞。胚囊的发育为蓼型, 四分体线形排列, 合点端大孢子发育成八核胚囊。受精后, 胚乳核先于受精卵进行分裂, 胚乳的发育为核型。胚的发育为柳叶菜型灯芯草变型。通过比较, 嵩草属植物大小孢子的发育、胚珠的结构、胚囊的发育、胚乳的发育和胚的发育与莎草科中其它类群一致。所以, 根据胚胎学资料, 嵩草属及其近缘属应保留在莎草科中,不该另立为嵩草科。     

模拟增温对青藏高原多年冻土区小嵩草和藏嵩草生长与抗氧化特征的影响

采用开顶式增温小室(OTCs)方法模拟气候变暖,分别选取青藏高原腹地风火山地区高寒小嵩草草甸和高寒藏嵩草沼泽草甸优势物种小嵩草和藏嵩草为研究对象,对比分析增温处理下两种优势物种叶片的形态与生理特征变化,从而探索高寒植物对气候变暖的内在响应机理.结果表明: 增温显著增加了小嵩草叶片长度(40.0%)和叶片数量(72.7%),也显著增加了藏嵩草株高(11.9%)和叶片长度(19.3%),促进了两种优势植物的形态生长和地上生物量增加.增温处理下小嵩草和藏嵩草叶片的膜透性(电导率),活性氧(过氧化氢和超氧阴离子自由基),超氧化物歧化酶、过氧化物酶、抗坏血酸过氧化物酶和过氧化氢酶活性,丙二醛含量均没有显著变化.但抗坏血酸和游离脯氨酸含量在藏嵩草叶片内分别显著增加了29.8%和53.8%,而在小嵩草叶片内没有明显变化.可见,增温下小嵩草和藏嵩草均能够维持正常的抗氧化水平,以维持该区域优势植物生长;但藏嵩草生理过程对增温更加敏感.     

中国顶丝藻科(Acrochaetiaceae)新记录Ⅴ

继续报道中国顶丝藻科新记录4个种;豪氏旋体藻Audouinella howei;矮生旋体藻A.humilis;斑点旋体藻A.macula;细枝旋体藻A.tenuissima。     

Ploidy in the alpine sedge Kobresia pygmaea (Cyperaceae) and related species: combined application of chromosome counts,new microsatellite markers and flow cytometry

Polyploidy is a fundamental mechanism in evolution, but is hard to detect in taxa with agmatoploidy or aneuploidy. We tested whether a combination of chromosome counting, microsatellite analyses and flow cytometric measurements represents a suitable approach for the detection of basic chromosome numbers and ploidy in Kobresia (Cyperaceae). Chromosome counting resulted in 2n = 64 for Kobresia pygmaea and K. cercostachys, 2n = 58 and 64 for K. myosuroides, and 2n = 72 for K. simpliciuscula. We characterized eight microsatellite loci for K. pygmaea, which gave a maximum of four alleles per individual. Cross‐species amplification was tested in 26 congeneric species and, on average, six of eight loci amplified successfully. Using flow cytometry, we confirmed tetraploidy in K. pygmaea. Basic chromosome numbers and ploidy were inferred from chromosome counts and the maximum number of alleles per locus. We consider the basic numbers as x = 16 and 18, with irregularities derived from agmatoploidy and aneuploidy. Across all Kobresia taxa, ploidy ranged from diploid up to heptaploid. The combination of chromosome counts and microsatellite analyses is an ideal method for the determination of basic chromosome numbers and for inferring ploidy, and flow cytometry is a suitable tool for the identification of deviating cytotypes. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 22–35.     

Micro-Scale Restoration: A 25-Year History of a Southern Illinois Barrens

We studied vegetation change of a remnant barrens in southern Illinois over twenty‐five years. The study area was periodically burned between 1969 and 1993, but fire was excluded for a 16‐year period (1974–1989). During the study, the barrens supported a mixture of species whose preferred habitats ranged from prairie and open woodlands to closed forest communities. The herbaceous vegetation may be on a trajectory characterized by increasing dominance of woodland species and declining prairie species. Fire management temporarily reversed this trend, but it continued once fire was excluded. Reintroduction of prescribed burning in 1990–1993 altered the vegetation trajectory but not back toward a species composition comparable to that present on the site before cessation of fire management after 1973. Following interruption of prescribed burning, tree basal area more than doubled, and density showed a 67% increase between premanagement conditions in 1968 and 1988. Salix humilis (prairie willow) density had significant negative correlations with tree density and basal area. However, there was no consistency in response of shrub species on the site to the varied site conditions over time. Fire management on the site may not recover the historic barrens that occurred on the site. Nevertheless, consistent fire management will drive vegetation changes toward increasing abundance of prairie and open woodland species that would otherwise be lost without burning.     

高原鼠兔对小嵩草草甸的破坏及其防治

1997～2000 年在青海省果洛州达日县, 通过测定不同程度退化草地、人工草地和除杂草地中高原鼠兔种群数量的变化以及对草地的破坏程度, 分析了草地植物群落变化对高原鼠兔种群数量的影响。结果表明: 随草地退化程度的加重, 高原鼠兔种群数量相应升高, 重度退化草地中高原鼠兔种群数量降低, 是由食物资源不足引起。不同程度退化草地之间高原鼠兔种群数量差异极显著( t_{未退化与轻度}= 25.369 7 , t_{未退化与中度}= 25.55 ,t_{未退化与重度}= 36.406 0 , t_{轻度与中度}= 23.279 4 , t_{轻度与重度}= 14.343 9 , t_{中度与重度}= 20.178 5 , df = 3 , p < 0.001) 。高原鼠兔对草地的破坏面积与平均单坑面积呈显著的相关关系( F = 220146 , df = 3 , P < 0.001) 。在草地达到重度退化以前, 高原鼠兔的种群密度升高, 对草地的危害则加重。草地植物群落空间结构的变化直接影响高原鼠兔的种群数量, 当植物群落高度增加时, 其种群数量开始减少, 反之则增加。