花楸树种子散布、萌发与种群天然更新的关系

花楸树是我国东北林区重要的非木质资源树种,其实生天然更新不良.本文通过研究花楸树种子散布、土壤种子库及种子萌发出土过程,分析花楸树实生天然更新的影响因素.结果表明：自然散落的花楸树果实96.1%分布于母株2 m范围内,凋落物层和土壤表层（0～2 cm）的种子数占土壤种子库总数的97.0%;不同季节花楸树土壤种子库种子数量差别很大,当年11月上旬种子数量最多,达(257.7±69.2)粒·m^-2;翌年7月下旬种子数量最少,仅为(2.9±2.9)粒·m^-2;温度不是花楸树种子萌发出土过程的限制因子,0 ℃～5 ℃时幼苗出苗率达(67.5±6.6)%,但对其出苗速率影响显著.土壤含水量为50%时,花楸树出苗率最高,达(74.7±4.2)%;含水量为60%时,幼苗死亡率最低,为(32.6±0.6)%.花楸树种子的散布格局和土壤种子库的时空分布格局影响种子的萌发出土过程,进而影响其种群的天然更新.     

黄山花楸种群遗传多样性研究

利用RAPD技术,对黄山花楸(Sorbus amabilis)自然分布区的13个自然种群的遗传多样性进行了研究,从40个10碱基随机引物中筛选出能产生稳定多态性标记的引物14个,共扩增出105个位点,其中多态性位点30个,占28．6％,应用UPGMA法和Neighbor-Joining法对遗传距离进行聚类分析构建树系图。结果表明,黄山花楸自然种群具有较低的遗传多样性,对环境变化的适应能力较差;其种群间的遗传差异与其地理分布有关;黄山花楸自身的特殊进化历史和人为砍伐以及自然灾害(火灾、病虫害等)和小种群的遗传漂变作用是黄山花楸遗传多样性水平低的主要原因,也是其濒危的主要原因。     

多蕊石灰树属应与花楸属合并

多蕊石灰树属与花楸属在性状上没有明显区别,故应予以合并。提出了墨脱花楸Sorbus medogensis 这一新名称。     

新疆天山中部北山羊社群结构

2013年10月至2014年9月,于天山中部天格尔山脉乌鲁木齐河源区研究了北山羊的社群结构。将其集群类型划分为雄性群、雌幼群、混合群和独羊4类。共统计北山羊497群,总计6 427只。北山羊最大集群为100只,最小群为1只,全年平均群大小为（12.93±0.65）只。其中春季（14.83±1.35）只,夏季（14.16±1.65）只,秋季（15.17±1.69）只,冬季（9.32±0.74）只。冬季北山羊平均集群大小显著低于其他三个季节。混合群的平均群大小最大,其余依次为雌幼群和雄性群。Kruskal-Wallis H检验结果表明各社群类型群大小差异极显著。北山羊多以2-7只的小群活动,占到总遇见频次比例的41.05%,8-20只群占32.80%,20只以上大群出现最少,占17.71%。在4种集群类型中,雌幼群出现频率最高,占51.91%,其次依次为混合群、雄性群和独羊。卡方检验结果表明4个季节间4种社群类型的出现频次差异显著。研究结果显示,北山羊在发情期混群,非繁殖期同性集群。受环境因素和自身生理周期的影响,其集群大小、集群类型均随季节变化而变化。     

Competitive success of southern populations of Betula pendula and Sorbus aucuparia under simulated southern climate experiment in the subarctic

Global warming has been commonly accepted to facilitate species’ range shifts across latitudes. Cross‐latitudinal transplantations support this; many tree species can well adapt to new geographical areas. However, these studies fail to capture species’ adaptations to new light environment because the experiments were not designed to explicitly separate species’ responses to light and temperature. Here we tested reaction norms of tree seedlings in reciprocal transplantations 1,000 km apart from each other at two latitudes (60°N and 69°N). In contrast to past studies, we exposed our experimental plants to same temperature in both sites (temperature of 60°N growing site is recorded to adjust temperature of 69°N site in real time via Internet connection) while light environment (photoperiod, light quality) remained ambient. Shoot elongation and autumn coloration were studied in seedlings of two deciduous trees (Betula pendula and Sorbus aucuparia), which were expected to respond differently to day length. Sorbus as a member of Rosaceae family was assumed to be indifferent to photoperiod, while Betula responds strongly to day length. We hypothesized that (1) southern and northern populations of both species perform differently; (2) southern populations perform better in both sites; (3) autumn phenology of southern populations may delay in the northern site; (4) and Sorbus aucuparia is less dependent on light environment. According to the hypotheses, shoot elongation of northern population was inherently low in both species. An evolutionary consequence of this may be a competitive success of southern populations under warming climate. Southern population of B. pendula was delayed in autumn coloration, but not in growth cessation. Sorbus aucuparia was less responsive to light environment. The results suggest that light provides selection pressure in range shifts, but the response is species dependent.     

两种荒漠生境条件下泡泡刺水分来源及其对降水的响应

泡泡刺通常以灌丛沙堆的形式存在,具有很强的生态适应性,在防风固沙、抗旱耐盐等方面具有独特的功能,但是水分条件仍然是限制其生存和发展的关键因素.为了明确泡泡刺在不同荒漠生境条件下的水分利用策略,研究了河西走廊临泽绿洲边缘沙质和砾质生境下泡泡刺的水分来源季节动态特征以及对不同降雨事件的响应程度.测定了两种生境下泡泡刺茎水和不同水源(降水、土壤水和地下水)的氧稳定同位素(δ¹⁸O)值,结合IsoSource模型计算了不同水源对泡泡刺水分来源的贡献比例.结果表明:两种生境下泡泡刺茎水δ¹⁸O值及其水分来源都存在显著的季节变化特征,沙质生境下泡泡刺在降水较少的春季和秋季主要利用地下水,其贡献率可达50%以上;而砾质生境下的泡泡刺无法利用深达11.5 m地下水,其水分来源受降水控制,具有较大的季节变异性.两种生境下的泡泡刺对降水响应显著,但是降水过后,随着土壤含水量的快速减小,沙质生境下的泡泡刺转而以丰富的地下水为主要水分来源,而砾质生境下的泡泡刺只能利用降水入渗至较深层土壤的较少水分.因此,两种生境下泡泡刺不同的水分利用策略是导致其生长特征差异的主要原因,同时也表明泡泡刺具有较强的自我调节和适应能力.     

Fruit softening: evidence for pectate lyase action in vivo in date (Phoenix dactylifera) and rosaceous fruit cell walls

Background and AimsThe programmed softening occurring during fruit development requires scission of cell wall polysaccharides, especially pectin. Proposed mechanisms include the action of wall enzymes or hydroxyl radicals. Enzyme activities found in fruit extracts include pectate lyase (PL) and endo-polygalacturonase (EPG), which, in vitro, cleave de-esterified homogalacturonan in mid-chain by β-elimination and hydrolysis, respectively. However, the important biological question of whether PL exhibits action in vivo had not been tested.MethodsWe developed a method for specifically and sensitively detecting in-vivo PL products, based on Driselase digestion of cell wall polysaccharides and detection of the characteristic unsaturated product of PL action.Key ResultsIn model in-vitro experiments, pectic homogalacturonan that had been partially cleaved by commercial PL was digested to completion with Driselase, releasing an unsaturated disaccharide (‘ΔUA–GalA’), taken as diagnostic of PL action. ΔUA–GalA was separated from saturated oligogalacturonides (EPG products) by electrophoresis, then subjected to thin-layer chromatography (TLC), resolving ΔUA–GalA from higher homologues. The ΔUA–GalA was confirmed as 4-deoxy-β-l-threo-hex-4-enopyranuronosyl-(1→4)-d-galacturonic acid by NMR spectroscopy. Driselase digestion of cell walls from ripe fruits of date (Phoenix dactylifera), pear (Pyrus communis), rowan (Sorbus aucuparia) and apple (Malus pumila) yielded ΔUA–GalA, demonstrating that PL had been acting in vivo in these fruits prior to harvest. Date-derived ΔUA–GalA was verified by negative-mode mass spectrometry, including collision-induced dissociation (CID) fragmentation. The ΔUA–GalA:GalA ratio from ripe dates was roughly 1:20 (mol mol^–1), indicating that approx. 5 % of the bonds in endogenous homogalacturonan had been cleaved by in-vivo PL action.ConclusionsThe results provide the first demonstration that PL, previously known from studies of fruit gene expression, proteomic studies and in-vitro enzyme activity, exhibits enzyme action in the walls of soft fruits and may thus be proposed to contribute to fruit softening.     

Metabolism of <Superscript>14</Superscript>C-glycine as a substrate for photorespiration of the leaf at different developmental stages of ephemeroides

The metabolism of ¹⁴C-glycine (a substrate for photorespiration) was studied in the light and in darkness under natural CO₂ concentration (0.03%) in the leaves of ephemeroides Scilla sibirica Haw. and Ficaria verna Huds. at different developmental stages. Using one and the same sample, potential photosynthesis (at 1% CO₂), true photosynthesis (at 0.03% CO₂), and leaf respiratory capacity were measured by the radiometric and manometric methods, respectively. All measurements were performed at 15°C, an average temperature during ephemer growth. It was found that, in the white zone of the Scilla leaf, the rate of CO₂ evolution resulting from metabolization of exogenous ¹⁴C-glycine was similar in the light and in darkness. In the green zone of the Scilla leaf and in the green leaf of Ficaria, both ¹⁴C-glycine absorption and ¹⁴CO₂ evolution were lower in the light as compared with darkness, which is explained by CO₂ reassimilation. In all treatments of both plant species, a specific inhibitor of glycine decarboxylase complex (GDC), aminoacetonitrile (5 mM) suppressed CO₂ evolution by 20–40%. It was concluded that in ephemeroides mitochondrial GDC, responsible for CO₂ evolution in photorespiration, is formed at the earliest stage of leaf development. This indicates that photorespiration can occur simultaneously with the development of the leaf photosynthetic activity. On the basis of the assumption that carbon losses in the form of CO₂ evolved during photorespiration comprise 25% of true photosynthesis, it was calculated that, in ephemer leaves, the highest rates of photorespiration and photosynthesis were attained during flowering when the leaf area was the largest and the rate of dark respiration was reduced by 1.5–2.0 times. The highest rates of dark respiration were observed in the beginning of growth. In senescing leaves by the end of the plant vegetation, potential photosynthesis and true photosynthesis were reduced, whereas dark respiration remained essentially unchanged. It is concluded that the high rates of potential and true photosynthesis are characteristic of ephemeroides when they complete their short developmental program in early spring (at 15°C); theoretically, photorespiration also occurs at a high rate during this period, when this process provides for a defense against the threat of photoinhibition at low temperature and high insolation.     

芦笋木蠹蛾的生物学特性

芦笋木蠹蛾Isoceras sibirica(Alpheraky)是危害芦笋的重要害虫。该虫在山西省运城市1年发生1代,以老熟幼虫在土中结薄茧越冬。翌年3~4月老熟幼虫由深土层上移至地表土壤结茧化蛹。4月中下旬为化蛹高峰。5月上中旬为蛹羽化高峰期。6月上旬为卵孵化高峰期。幼虫为害期为5月下旬至10月下旬。对该虫的形态、生活习性和发生规律作了描述和报道。