内生真菌种类和母本基因型对内生真菌-禾草共生体叶形状和叶面积的影响

Epichloë内生真菌感染能够影响宿主植物的生长发育, 但关于内生真菌感染对宿主植物叶形状和叶面积的研究很少。该研究以羽茅(Achnatherum sibiricum)为实验材料, 采用长宽系数计算和扫描测定叶面积相结合的方法探究内生真菌种类和羽茅母本基因型对羽茅-内生真菌共生体叶形状和叶面积的影响。结果表明: 内生真菌感染与否、内生真菌种类和宿主母本基因型对反映叶形状的叶校正系数、叶片长度、宽度和长宽比均无显著影响, 经计算与验证, 确定了羽茅叶片的校正系数为0.594 9。采用该校正系数及叶长宽计算的叶面积与实测叶面积无显著差异, 且二者均未受到内生真菌感染与否、内生真菌种类或宿主植物母本基因型的显著影响。     

9种观赏草苗期耐盐性评价及NaCl胁迫对芨芨草生长的影响

采用砂培法,对质量浓度0(对照)、5、10、15、20和30 g.L-1NaCl胁迫条件下长芒草(Stipa bungeana Trin.)、丽色画眉草〔Eragrostis spectabilis(Pursh)Steud.〕、狼尾草〔Pennisetum alopecuroides(L.)Spreng〕.、‘小兔子’狼尾草(P.alopecuroides‘Little Bunny’)、拂子茅(Calamagrostis brachytricha Steud.)、野古草〔Arundinella hirta(Thunb.)Tanaka〕、远东芨芨草〔Achnatherum extremiorientale(Hara)Keng〕、芨芨草〔A.splendens(Trin.)Nevski〕和须芒草(Andropogon scoparius Michx.)幼苗的存活率和死亡率进行了分析,并根据植株死亡率、植株存活或出现死亡的NaCl质量浓度和5 g.L-1 NaCl胁迫条件下6个生长指标的聚类分析结果对9种观赏草的耐盐性进行了评价;在此基础上,对NaCl胁迫条件下耐盐性最强的芨芨草生长指标的变化进行了详细分析。结果表明:采用植株死亡率、植株存活或出现死亡的NaCl质量浓度以及生长指标的聚类分析结果都可对供试9种观赏草的耐盐性进行评价,评价结果有一定的差异但表现出相似的趋势;综合3种方法的评价结果,9种观赏草的耐盐性可被分为4个等级:芨芨草最强;狼尾草、‘小兔子’狼尾草、丽色画眉草和长芒草较强;须芒草中等;拂子茅、远东芨芨草和野古草最弱。在NaCl胁迫条件下,芨芨草栽培基质及其渗出液的电导率随NaCl质量浓度的提高逐渐增大;而芨芨草的不同生长指标对NaCl胁迫的响应有差异,其中,NaCl胁迫对芨芨草根长的影响较小;随NaCl质量浓度的提高,芨芨草的苗高、分蘖数、根数、茎叶干质量和根干质量以及叶绿素相对含量均逐渐降低,而根冠比逐渐增大。在NaCl质量浓度高于10 g.L-1条件下,芨芨草幼苗可以存活;而在NaCl质量浓度不高于10 g.L-1条件下,芨芨草幼苗可以维持生长。实验期间的极端高温及极端低温以及栽培基质电导率的变化均对芨芨草幼苗的生长和耐盐性有一定的影响。     

Insect growth regulating and antifeedant effects of neem extracts and azadirachtin on two aphid species of ornamental plants

Leaf disc choice test bioassay demonstrated that formulated neem seed extracts were highly deterrent and growth regulatory to rose aphid,Microsiphum rosae (L.) and Chrysanthemum aphid,Macrosiphoniella sanbornii (Gillete). Effective concentrations to produce 50% feeding deterrence was 0.80 and 0.84% respectively for 2nd instar nymphs irrespective of bioassay duration. The disruption of aphid feeding was related to the presence of azadirachtin concentration in the extract. The toxicity on contact from the leaf surface or via topical application due to azadirachtin was significantly different and topical treatment was at least 7 times more effective for both species. Thus growth regulatory effects of azadirachtin were influenced by the host plant and the stage of treatment. Field evaluation with formulated neem extracts revealed the effect to be more of growth regulatory nature thereby showing that azadirachtin is a physiological toxin for aphid species. Neem seed extracts reduced the population of aphid on respective host plants significantly, EC₅₀ values being 0.88 and 0.96% forM. rosae andM. sanbornii respectively.     

干旱胁迫对喀斯特地区野生茶树幼苗生理特性及根系生长的影响

以贵州喀斯特地区4种野生茶树(Sect Thea(L.)Dyer)无性系幼苗为材料,采用盆栽控水方法研究其对干旱胁迫的生理生长响应,初步评价其抗旱性,并采用田间模拟持续干旱试验进行验证。结果表明:(1)随着干旱胁迫程度的加强,4种野生茶树叶片的相对含水量逐渐降低;细胞质膜透性、丙二醛(MDA)含量和可溶性糖含量均呈上升趋势;游离脯氨酸含量和超氧化物歧化酶(SOD)活性先升后降;过氧化物酶(POD)活性除秃房茶随胁迫程度加强呈上升趋势外,其他种均呈先升后降趋势。(2)随着干旱胁迫程度的加强,4种茶树幼苗总生物量干重均逐渐下降,根冠比先升后降;根系总长除在秃房茶中呈先升后降趋势外,在其他3个种中均逐渐下降;根系总表面积、根系总体积在大理茶和茶中逐渐下降,而在大厂茶和秃房茶中先升后降;根系平均直径在秃房茶中逐渐降低,大厂茶中先升后降,茶中逐渐升高;根系活力在大理茶中逐渐下降,在其他3种中均先升后降;而比叶面积则在大厂茶中呈下降趋势,在其他3种中均先升后降。(3)基于生长生理指标的隶属函数抗旱性评价结果表明,MDA含量和细胞质膜透性与野生茶树抗旱性密切相关,4种野生茶树幼苗的抗旱顺序为秃房茶(Camellia gymnogyna Chang)大厂茶(Camellia tachangensis F.C.Zhang)茶(Camellia Sinensis(L.)-O.Kuntze)大理茶(Camellia taliensis(W.W.Smish)),田间持续干旱试验验证了基于隶属函数抗旱性评价方法的准确性和可靠性。     

模拟氮沉降和干旱对准噶尔盆地两种一年生荒漠植物生长和光合生理的影响

氮素和水分是荒漠生态系统的两个主要限制因子, 研究两者对荒漠植物的效应有助于深入了解荒漠生态系统对全球变化的响应。该文选择准噶尔盆地荒漠地区两种常见的一年生植物涩荠(Malcolmia africana)和钩刺雾冰藜(Bassia hyssopifolia), 设置0、0.18和0.72 g N·m ^-2·week ^-13个施氮浓度和湿润与干旱两个土壤水分处理, 研究模拟氮沉降增加和干旱对其生长和光合生理的影响。结果表明: (1)两种植物的根长、根重、叶片数、叶面积、总生物量和冠根比均随着施氮浓度的增加而增加, 干旱能够抑制氮对植物生长的促进作用, 但是, 氮的增加同时也能部分缓解干旱对植物生长的影响。与钩刺雾冰藜相比, 涩荠的根长、生物量和冠根比更易受氮增加和干旱的影响。(2)两种植物的最大净光合速率、叶绿素含量、可溶性蛋白含量随着氮浓度增加而增加, 但涩荠和钩刺雾冰藜对氮增加和干旱的生理响应也有所不同, 涩荠的响应更加敏感。两种植物对氮沉降和干旱胁迫响应的差异可能是其生活型等生物学特性差异所引起。通过对两种一年生植物的生长和光合生理分析表明, 在古尔班通古特沙漠, 春季丰富的降水和氮素增加将有利于涩荠和钩刺雾冰藜的生长和生产力的增加, 相对地下生长, 地上部分增加更显著。当干旱季节来临时, 氮的增加又能够在一定程度上降低干旱对这两种植物的负效应, 说明其对干旱具有一定的生态补偿作用。     

Interactions of drought and low temperature stress on lipid and fatty acid composition of cucumber genotypes differing in growth response at suboptimal temperature

The effects of drought stress and/or low temperature stress on total lipid and phospholipid content and fatty acid composition of leaves of cucumber ( Cucumis sativus L.) genotypes differing in growth response at suboptimal temperature were studied. Both drought and low temperature resulted in reduced growth, especially in cv. Farbio, the genotype least tolerant to low temperature. Drought resulted in an increase in total lipid and phospholipid per g fresh weight. On a lipid basis no change in phospholipids or fatty acid content was observed. The fatty acid composition was changed by drought and low temperature, resulting in an increase in the degree of unsaturation. The genotype-specific reaction to treatment for total lipid content and the degree of unsaturation point to the possibility of a genetic origin for drought-induced lipid changes, which may be used in a breeding program for improved growth at suboptimal temperature.     

Lifetable demography and population growth of the rotifer Brachionus angularis in Kenya: influence of temperature and food density

Lifetable demography and reproductive traits of a Kenyan strain of the rotifer Brachionus angularis were investigated using individual and small batch culture approaches. The rotifer was identified morphologically before conducting studies at 20, 25 and 30 °C, using Chlorella vulgaris at 2.5 × 10⁵ to 2.5 × 10⁷ cells ml^–1. The rotifers were highly fecund, producing 2.11 ± 0.07 offspring female^–1 day^–1 and reproductive, producing 8.43 ± 0.24 offspring female^–1 at 25 °C with 2.5 × 10⁶ algal cells ml^–1. The highest intrinsic rate of natural increase (0.74 ± 0.02 d^–1), specific population growth rate (0.49 ± 0.01), longest life expectancy at hatching (12.41 ± 0.28 d) and shortest generation time (2.87 ± 0.03 d) also occurred at 25 °C with 2.5 × 10⁶ algal cells ml^–1. The duration of hatching to first spawning was shortest (2.86 ± 0.21 h) at 30 °C with 2.5 × 10⁷ algal cells ml^–1 and longest (8.83 ± 0.39 h) at 20 °C with 2.5 × 10⁵ algal cells ml^–1. The highest population density (255.7 ± 12.6 ind. ml^–1) was realised at 25 °C with 2.5 × 10⁶ cells ml^–1 on Day 8, whereas the lowest population density (122.0 ± 3.6 ind. ml^–1) was realised at 20 °C with 2.5 × 10⁵ cells ml^–1 on Day 8. The lorica length and width of the Kenyan strain of B. angularis are 85.6 ± 3.1 µm and 75.4 ± 3.6 µm, respectively. The rotifer optimally reproduces at 25 °C when fed with 2.5 × 10⁶ algal cells ml^–1.     

Effects of cadmium stress on seed germination,seedling growth and antioxidative enzymes in <Emphasis Type=Italic>Achnatherum inebrians</Emphasis> plants infected with a <Emphasis Type=Italic>Neotyphodium</Emphasis> endophyte

The effects of cadmium (Cd) on germination, and antioxidative enzyme activity (AEA) involving superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase, and on amounts of malondialdehyde and proline present within Achnatherum inebrians, were determined for specimens infected (E+) vs. non-infected (E−) by Neotyphodium gansuense, and cultivated in the presence of various concentrations of CdCl₂ (0, 50, 100, 200 and 300 μmol/l). Under high Cd concentrations (100, 200 and 300 μM), E+ (vs. E−) specimens exhibited a higher germination rate and index, and higher values for shoot length, root length and dry biomass, but there was no significant difference (P > 0.05) under low Cd concentrations (0 and 50 μM). AEA and the proline content increased, but malondialdehyde content declined in the E+ (vs. E−) specimens under high Cd concentrations (100, 200 and 300 μM). There was no significant difference (P > 0.05) under low Cd concentrations (0 and 50 μM). Endophyte infection was concluded to be of benefit to the germination and anti-oxidative mechanisms within A. inebrians under plant exposures to high CdCl₂ concentrations.     

Quantitative genetic and translocation experiments reveal genotype‐by‐environment effects on juvenile life‐history traits in two populations of Chinook salmon (Oncorhynchus tshawytscha)

Understanding the genetic architecture of phenotypic plasticity is required to assess how populations might respond to heterogeneous or changing environments. Although several studies have examined population‐level patterns in environmental heterogeneity and plasticity, few studies have examined individual‐level variation in plasticity. Here, we use the North Carolina II breeding design and translocation experiments between two populations of Chinook salmon to detail the genetic architecture and plasticity of offspring survival and growth. We followed the survival of 50 800 offspring through the larval stage and used parentage analysis to examine survival and growth through freshwater rearing. In one population, we found that additive genetic, nonadditive genetic and maternal effects explained 25%, 34% and 55% of the variance in larvae survival, respectively. In the second population, these effects explained 0%, 24% and 61% of the variance in larvae survival. In contrast, fry survival was regulated primarily by additive genetic effects, which indicates a shift from maternal to genetic effects as development proceeds. Fry growth also showed strong additive genetic effects. Translocations between populations revealed that offspring survival and growth varied between environments, the degree of which differed among families. These results indicate genetic differences among individuals in their degree of plasticity and consequently their ability to respond to environmental variation.     

Temporal changes in root growth and 15N uptake and water relations of two tussock grass species recovering from water stress

Physiological responses of Agropyron desertorum and Pseudoroegneria spicata , two common cold desert perennial tussock grass species of the North American Great Basin, were evaluated during and after a period of imposed drought in a pot study. The timing and the pattern of response of leaf water potential (Ψ₁), stomatal conductance (g_s), and root growth were strikingly similar in both species during and after drought. The severity of stress influenced the magnitude of Ψ₁ and g_s, but had little effect on the timing of these responses. Although drought inhibited total root length in prestressed plants, within 4 days after relief of drought both species showed similar increases in root growth which exceeded those of the control. Despite similarities in their root growth responses to increased soil water availability, the two grasses differed in their capacity to restore N uptake following drought. By 14 days after rewatering, N uptake in the prestressed Agropyron had recovered to levels of control plants, although both root biomass and root lenght were much less than those of the controls. This is attributed to elevated root uptake kinetics. Restoration of N uptake by prestressed Pseudoregneria was much less effective during the same period.     

干旱对东北春玉米生长发育和产量的影响

选取玉米品种丹玉39为供试材料,利用大型农田水分控制试验场,采用大田池栽方式,在玉米三叶-拔节期、拔节-吐丝期、吐丝-乳熟期分别开展中度干旱胁迫及复水控制对比试验,分析3个关键生育时期干旱胁迫对春玉米生长发育和产量的影响.结果表明：与水分适宜对照（CK）相比,三叶-拔节期遭受干旱胁迫后,全生育期推迟13 d,至拔节普遍期,株高偏低29.8%,叶面积偏小41.2%,复水后,株高和产量得到较大程度恢复,果穗性状和最终产量差异不大;拔节-吐丝期遭受干旱胁迫后,全生育期缩短7 d,至吐丝普遍期,株高偏低18.6%,叶面积偏小14.1%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降6.9%、19.1%、28.1%和29.4%,空秆率增加13.3%;吐丝-乳熟期遭受干旱胁迫后,全生育期缩短15 d,生长至乳熟普遍期,株高偏低2.3%,叶面积偏小37.3%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降9.2%、24.1%、30.8%和27.9%,空秆率增加24.5%.拔节-吐丝期、吐丝-乳熟期干旱胁迫处理并复水后,玉米株高恢复不明显,产量降幅显著.     

Effects of drought on the growth and resource use efficiency of two endemic species in an arid ecotone

Anthropogenic activities and environmental changes have had a significant effect on the fishery ecosystem, biological characteristics, and population dynamics of marine fishes. Overfishing threatens the sustainability of many populations. We evaluated changes in the biological characteristics, distribution, and abundance of Cleisthenes herzensteini using bottom trawl survey data collected from 1985 to 2010 in the central and southern Yellow Sea. The dominant body length of C. herzensteini during spring was 80–160 mm in 1986, 60–160 mm in 1998, and 41–80 mm and 111–170 mm in 2010. During summer, the dominant body length was 80–180 mm and 130–169 mm in 2000 and 2007, respectively. During autumn, the dominant body length was 60–160 mm, 100–180 mm, and 90–149 mm in 1985, 2000, and 2009, respectively. During winter, the dominant body length was 80–200 mm, 120–220 mm, and 100–200 mm in 1985, 1999, and 2010, respectively. The dominant body length decreased gradually from 1985 to 2010 (excluding spring, 2010), illustrating the “miniaturization” of the C. herzensteini population. Growth was significantly different between male and female individuals, with male individuals forming a “smaller-size type”. The sex ratio of C. herzensteini was relatively stable during spring and summer, but significantly different during autumn and winter. The diet of C. herzensteini also changed significantly from 1985 to 2010. During 1985–1986, the diet consisted primarily of Crangon affinis, Eualus sinensis and Gammaridae species. C. affinis, Engraulis japonicus, and Ammodytes personatus were dominant during 1998–2000, whereas C. affinis was the dominant prey species during 2009–2010. Thus, there was a clear decrease in dietary diversity, with a shift to benthos shrimp, particularly C. affinis, which accounted for 82.58% of the total diet (by weight) in 2010. The gastric vacuous rate also decreased in every season and the gonad developmental stage changed with each season. The distribution of C. herzensteini shifted northward and offshore and became more concentrated. The average catch per haul of C. herzensteini decreased in spring and autumn. The average catch per haul ranged from 1.44 kg h^-1 to 0.14 kg h^-1 in spring and the percentage by weight ranged from 6.53% to 1.28%. The average catch per haul ranged from 3.03 kg h^-1 to 0.26 kg h^-1 in autumn and the percentage by weight ranged from 8.00% to 0.60%. The average catch per haul increased significantly during summer, ranging from 0.18 kg h^-1 to 0.58 kg h^-1, with a percentage by weight of 0.03–0.80%. The average catch per haul was relatively stable in winter (around 1.00 kg h^-1), but the percentage by weight gradually increased during 1985–2010. Taken together, our results suggested that the population structure, diet composition, and distribution of C. herzensteini had been altered during the last three decades. To address this, it is essential to initiate measures to conserve the C. herzensteini resource.     

Greater growth stability of trees in marginal habitats suggests a patchy pattern of population loss and retention in response to increased drought at the rear edge

Species rear range edges are predicted to retract as climate warms, yet evidence of population persistence is accumulating. Accounting for this disparity is essential to enable prediction and planning for species’ range retractions. At the Mediterranean edge of European beech‐dominated temperate forest, we tested the hypothesis that individual performance should decline at the limit of the species’ ecological tolerance in response to increased drought. We sampled 40 populations in a crossed factor design of geographical and ecological marginality and assessed tree growth resilience and decline in response to recent drought. Drought impacts occurred across the rear edge, but tree growth stability was unexpectedly high in geographically isolated marginal habitat and lower than anticipated in the species’ continuous range and better‐quality habitat. Our findings demonstrate that, at the rear edge, range shifts will be highly uneven and characterised by reduction in population density with local population retention rather than abrupt range retractions.     

Comparison of the effects of canopy and understory nitrogen addition on xylem growth of two dominant species in a warm temperate forest,China

Understanding the effect of increasing atmospheric nitrogen (N) deposition on xylem growth of trees is critical to predict tree growth and carbon sequestration under global change. Canopy N addition (CAN) is generally believed to realistically simulate atmospheric N deposition on terrestrial ecosystems given it takes all processes of N deposition from forest canopy to belowground into account. However, whether CAN is more effective in reflecting the effect of atmospheric N deposition on xylem growth of trees than understory N addition (UAN) has been rarely reported. To address the question, we conducted a CAN vs. UAN experimental study to weekly monitor xylem growth of two dominant broadleaf species (Quercus acutissima Carruth. and Quercus variabilis Blume) in a warm temperate forest of China during 2014–2015. Weekly xylem increment during the two years was measured. Mixed-effects models were used to quantify the effects of N addition on xylem growth and detect the differences among treatments. We found that CAN of 50 kg N ha⁻¹ yr⁻¹ plays a more significant role in promoting xylem growth of Q. acutissima than UAN of 50 kg N ha⁻¹ yr⁻¹, and significantly enhanced the formation of differentiating xylem (zones of radial enlarging and wall-thickening cells) of Q. acutissima in the early growing season (April-June) and the rate of xylem increment, but no significant difference in xylem increment of Q. variabilis was detected between CAN50 and UAN50. This is the first study to quantitatively demonstrate that previous UAN studies may have underestimated the effects of atmospheric N deposition on tree growth by ignoring the N interception through forest canopy. Furthermore, our study also suggested a species-specific response of xylem growth to N addition. Under a certain amount of atmospheric N deposition in the future, the xylem increment of Q. acutissima may be superior to that of Q. variabilis.     

Plant architecture,growth and biomass allocation effects of the invasive pathogen myrtle rust (Austropuccinia psidii) on Australian Myrtaceae species after fire

In 2010, the parasitic fungus Austropuccinia psidii (myrtle rust) was detected in Australia. Austropuccinia psidii infects immature growth of myrtaceous species. Many of Australia’s myrtaceous species occur within fire‐prone vegetation communities and have the capacity to resprout after fire. Therefore, it is likely that new post‐fire growth may be vulnerable to A. psidii infection, causing subsequent flow‐on effects to species’ persistence and community dynamics. The aim of this study was to test the impacts of A. psidii on native Australian Myrtaceae species after fire. We grew eight native susceptible species in a glasshouse experiment before burning them and inoculating the resprouting new growth of half the plants with A. psidii. We assessed the effect of A. psidii on the architecture, growth and biomass allocation of our study species. Although general patterns were observed across species, results were found to be species‐specific. Austropuccinia psidii significantly reduced the height of two of the eight species (Callistemon citrinus and Eucalyptus moluccana), but none of the species had increased branching. As expected, specific leaf area was lower (9%) in inoculated plants – although only significant for C. citrinus and E. dalrympleana – and leaf biomass was greater (15%), but significant for Angophora costata only. Finally, biomass allocation did not significantly differ between infection treatments. We can conclude that the effect of A. psidii infection on fire‐damaged plants has significant impacts on plants at the species level, which may have flow‐on effects at the community level, especially after repeated infections. Furthermore, these impacts may be exacerbated in the future under climate change, as the predicted increase in frequency and intensity of fires across Australia will result in more frequent new growth availability, providing more opportunities for A. psidii infection.     

Synergistic effects of cadmium and NaCl on the growth,photosynthesis and ion content in wheat plants

The addition of NaCl to cadmium had significant synergistic effect on the wheat root and shoot fresh mass, relative growth rate and net assimilation rate, while showed no significant effects on the dry mass production, leaf area, leaf area ratio, leaf mass ratio and specific leaf area. Additive depression of the rate of photosynthesis and the stomatal conductance was recorded, while no significant effect on the transpiration rate was observed. The Cd stress disturbed the mineral nutrition of the wheat plants either directly or indirectly, NaCl markedly reduce the uptake and internal concentration of K and Ca in the shoot. The combination of cadmium and NaCl showed no additive effects on the content of ions in the root as well as in the shoot of wheat plants.     

干旱胁迫对两种油桐幼苗生长、气体交换及叶绿素荧光参数的影响

为了探究干旱胁迫对两种油桐(三年桐和千年桐)幼苗光合生理特性的变化及响应,采用盆栽试验,研究不同水分处理(正常供水、轻度干旱、中度干旱、重度干旱)对油桐幼苗生长、叶片气体交换及叶绿素荧光参数的影响。结果表明:与对照相比,轻度干旱胁迫对两种油桐生长、气体交换及叶绿素荧光参数无明显影响(P0.05);中度干旱及重度干旱使两种油桐的叶绿素SPAD值、生长量、净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、气孔限制值(L_s)、最大净光合速率(P_(nmax))、光饱和点(LSP)、表观量子效率(AQY)、暗呼吸速率(R_d)、最大光化学效率(F_v/F_m)、实际光化学量子效率(Φ_(PSⅡ))、电子传递速率(ETR)及光化学猝灭系数(q_P)显著下降(P0.05),且在重度干旱胁迫下迅速下降,胞间CO_2浓度(C_i)、水分利用效率(WUE)、光补偿点(LCP)、初始荧光(F_o)、非光化学猝灭系数(NPQ)显著升高(P0.05);中度干旱胁迫下油桐幼苗P_n的降低是由气孔因素及光合机构活性降低的非气孔因素共同引起的,而重度干旱胁迫下光合作用的下降主要是由光合机构活性降低的非气孔因素引起的。三年桐的光合机构活性及光合效率高于千年桐,对干旱胁迫的适应性较千年桐强。