Electrical impedance of white spruce shoots in relation to pressure-volume analysis and free sugar content

Electrical impedance measurements made on white spruce, Picea glauca (Moench) Voss, stems were related to shoot free sugar contents and to osmotic, turgor and water potential. During seasonal dormancy induction, there were commensurate increases in free sugar contents, osmotic potential at full turgor and impedance which resulted in linear relationships among these variables. When measured over the course of laboratory drying, impedance increased curvilinearly with decreasing relative water content. There was a linear increase in impedance with decreasing water potential, with a break point coincident with the turgor loss point, possibly attributed to disruption to current flow through broken plasmodesmatal connections between adjacent cells. This technique offers a non-destructive method to measure tissue free sugar content, and therefore, short- and long-term shifts in parameters historically derived from pressure-volume analysis.     

Non‐parametric habitat models with automatic interactions

Questions: Can a statistical model be designed to represent more directly the nature of organismal response to multiple interacting factors? Can multiplicative kernel smoothers be used for this purpose? What advantages does this approach have over more traditional habitat modelling methods? Methods: Non‐parametric multiplicative regression (NPMR) was developed from the premises that: the response variable has a minimum of zero and a physiologically‐determined maximum, species respond simultaneously to multiple ecological factors, the response to any one factor is conditioned by the values of other factors, and that if any of the factors is intolerable then the response is zero. Key features of NPMR are interactive effects of predictors, no need to specify an overall model form in advance, and built‐in controls on overfitting. The effectiveness of the method is demonstrated with simulated and real data sets. Results: Empirical and theoretical relationships of species response to multiple interacting predictors can be represented effectively by multiplicative kernel smoothers. NPMR allows us to abandon simplistic assumptions about overall model form, while embracing the ecological truism that habitat factors interact.     

Taste receptor activity and feeding behaviour reveal mechanisms of white spruce natural resistance to Eastern spruce budworm Choristoneura fumiferana

The pattern of feeding of Eastern spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera, Tortricidae) is compared on foliage from white spruce Picea glauca (Moench) Voss. (Pinaceae) trees previously determined to be susceptible and resistant to defoliation by budworm. No differences are observed in electrophysiological responses from taste sensilla to aqueous extracts of the two foliage types, nor is there a preference for either extract type in a choice test. Acetone extracts from the two foliage types are both preferred to a control sucrose solution, although neither elicits a preference relative to the other. These results suggest that there is no difference in phagostimulatory power of internal leaf contents of the two foliage types. Longer‐term observation of feeding behaviour in a no‐choice situation shows no difference in meal duration, confirming the lack of difference in phagostimulatory power. However, on average, intermeal intervals are twice as long on the resistant foliage, leading to an overall lower food consumption during the assay. This result suggests an anti‐digestive or toxic effect of the resistant foliage that slows behaviour and limits food intake. Previous research has shown that waxes of the resistant foliage deter initiation of feeding by the spruce budworm and that this foliage contains higher levels of tannins and monoterpenes. The data suggest that the resistant foliage contains a post‐ingestive second line of defence against the spruce budworm.     

Spruce budworm feeding and oviposition are stimulated by monoterpenes in white spruce epicuticular waxes

Monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. However, they are also known to act as long‐range insect attractants, as they are volatile and permeate forest airspaces. Moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes. We test their role in short‐range host plant choice by both adult females and larvae of a folivorous forest pest (Choristoneura fumiferana). We conducted laboratory assays testing the responses of Eastern spruce budworm to an artificial monoterpene mix (α‐pinene, β‐pinene, limonene, myrcene) and to white spruce (Picea glauca) epicuticular waxes in closed arenas. Ovipositing females preferred filter paper discs treated with P. glauca waxes to controls, and preferred the waxes + monoterpenes treatment to waxes alone. However, females showed no preference between the monoterpene‐treated disc and the control when presented without waxes. Feeding larvae prefered wax discs to control discs. They also consumed discs treated with realistic monoterpene concentrations and wax preferentially over wax‐only discs, but showed no preference between extremely high monoterpene concentrations and wax‐only controls. In an insect‐free assay, P. glauca epicuticular wax decreased monoterpene volatilization. These results suggest that P. glauca waxes and realistic concentrations of monoterpenes are stimulatory to both egg‐laying females and feeding larvae, and that their effects are synergistic.     

专一转化人参二醇类皂苷Rb1为Rd的真菌菌株的筛选

于2009年的7-10月间在辽宁省的桓仁,吉林省的集安、靖宇、抚松等药材产区采集人参及人参根际土壤样品45份.通过真菌分离和培养,共获得真菌菌株105株,经形态学鉴定分属于15属48种.通过活性筛选,得到具有转化人参总皂苷活性的菌株25株,其中菌株SR87和SR105对人参皂苷Rb1具有专一转化活性.通过TLC和HPL...     

国产木兰科6属植物柱头表面形态比较

用扫描电镜对中国产木兰科单性木兰属、木兰属、木莲属、含笑属、拟单性木兰属和观光木属的42种植物柱头表面形态进行观察.结果表明,42种木兰科植物的柱头均为干柱头,包含单细胞乳突型和多细胞乳突型两类.单性木兰属和观光木属植物是单细胞乳突型;木莲属、含笑属和拟单性木兰属植物是多细胞乳突型;木兰属中木兰亚属植物两型均有,而玉兰亚属则均为多细胞乳突型.结合其他证据,本文支持单性木兰属、木莲属、含笑属、拟单性木兰属和观光木属的建立,并认为在系统学问题较复杂的木兰属中,玉兰亚属是一个相对独立的单系类群,将其独立成属也不无道理,而木兰亚属可能不是一个单系类群,还需要进一步的深入研究,积累更多的性状数据.     

22种木莲属植物亲缘关系的SRAP分析(英文)

利用SRAP标记分析技术探讨了22种木莲属植物的遗传亲缘关系。选用13对SRAP引物组合对木莲属22个种的基因组进行分析。结果表明:22个种共扩增出981条DNA带,其中多态性条带占94.8%;在Nei’s遗传相似性系数0.70处,UPGMA聚类将22个种分为5个类群,在0.715分为9个亚类;22种木莲属植物的Nei’s遗传相似性系数变化范围为0.625(乳源木莲与球果木莲之间)～0.914(中缅木莲与滇南木莲之间),平均遗传相似性系数为0.696。其中中缅木莲、滇南木莲之间遗传相似性系数为0.914,两者亲缘关系最近。该结果支持将巴东木莲、乳源木莲、滇桂木莲分别作为独立的种。     

Wetland Waterbird Food Resources Increased by Harvesting Invasive Cattails

The conservation of many freshwater marsh waterbirds (i.e., waterfowl, shorebirds, wading birds, and secretive marshbirds) in the Laurentian Great Lakes requires managing invasive emergent macrophytes, which degrade waterbird habitat by creating dense, litter-clogged stands, and excluding plants that produce nutritionally balanced and high-energy food (seeds, tubers, and submerged aquatic vegetation). The most commonly used management approach in the United States Great Lakes region involves the application of herbicides, which can stimulate waterbird forage plants but does not address the accumulation of plant litter, the underlying cause of plant community diversity loss and habitat degradation. We experimentally evaluated the effects of an alternative approach, harvesting invasive plants and their litter followed by flooding, on plant communities, focusing on the effects of these treatments to increase the abundance of high-energy wetland plants. At the Shiawassee National Wildlife Refuge in Michigan, USA, we experimentally treated an invasive cattail (Typha × glauca)-dominated wetland in August and September of 2016, 2017, and 2018, using a randomized block design with 4 blocks and 3 treatments (sediment surface harvest, above ground harvest, and control). We monitored the effects of these treatments on the abundance and dominance of waterbird forage-producing plants, plant diversity, and plant communities prior to (Jul 2016) and during the summer following each treatment (late Jul or early Aug 2017, 2018, and 2019). Additionally, we used pre- and post-treatment waterbird use-day data collected at the unit scale and compared values with satellite imagery-derived land cover changes. Compared to control plots, 3 years of harvesting and flooding significantly increased plant species diversity, increased the abundance of waterbird seed- and tuber-producing plant species by 5 times, and increased annual plant dominance by more than 10 times, while substantially reducing all measures of cattail and its litter. Use-days increased for total waterbirds, including waterfowl and dabbling ducks, following treatment. Cattail cover decreased and open water and non-cattail emergent vegetation cover increased. Harvesting invasive plant biomass coupled with flooding promoted a plant community composition and structure beneficial to waterbirds. © 2020 The Wildlife Society.     

模拟酸雨胁迫对青冈幼苗光合特性和叶绿素荧光参数的影响

选择亚热带常绿阔叶林优势树种青冈幼苗为研究对象,设置3个酸雨处理：pH 2.5、pH 4.0、pH 5.6(CK),研究不同强度的模拟酸雨对青冈幼苗光合特性、叶绿素荧光参数和叶绿素含量的影响.结果表明：经过2年酸雨处理,青冈的净光合速率随着酸雨强度的增加而显著上升.pH 2.5、pH 4.0处理的酸雨增大了青冈的气孔导度和蒸腾速率,且对pH 2.5处理的影响更为显著.胞间CO₂浓度的大小顺序是pH 2.5>pH 5.6>pH 4.0.pH 2.5、pH 4.0处理青冈的最大净光合速率、光补偿点、光饱和点、暗呼吸速率显著高于对照,表观量子效率对酸雨胁迫不敏感.pH 2.5、pH 4.0处理青冈的PSⅡ原初光能转化效率和PSⅡ的潜在活性显著高于对照.青冈的叶绿素相对含量大小顺序是pH 2.5>pH 5.6>pH 4.0,且pH 2.5与pH 4.0之间有显著差异.说明青冈幼苗的光合参数、叶绿素荧光参数指标在pH 2.5和pH 4.0的酸雨处理下有所增加,且在pH 2.5强度下增加更为明显.     

Defensive compound concentration in boreal lichens in response to simulated nitrogen deposition

Nitrogen (N) deposition is expected to increase in northwestern Europe the next 50–100 years. The effects of higher N availability on lichens will presumably depend on their capacity to acquire carbon (C), that is, of the timing and duration of the wet and active state. If lichens respond like plants, their C and N status may affect their concentration of carbon-based secondary compounds (CBSCs), and thus their defence against herbivores, detrimental radiation, pathogens and parasites. In the present study we have manipulated N availability and timing and duration of the metabolically active state by spraying lichen transplants in an old spruce forest with rainwater or rainwater with added N corresponding to 50 kg N ha⁻¹ yr⁻¹. The spraying was applied either at night, in the morning or at noon to also investigate the effect of timing and duration of the active state. Concentrations of N, chlorophyll a (Chl a ) and CBSCs were measured before and after one summer's spraying of 10 thalli in each of four different lichen species; Alectoria sarmentosa, Lobaria scrobiculata, Platismatia glauca , and Xanthoria aureola . The added N was readily taken up by all the lichen species. A. sarmentosa, P. glauca , and X. aureola increased their Chl a concentration in response to increased N, while L. scrobiculata increased Chl a in response to increased active time. None of the studied species reduced their concentration of secondary compounds during the experimental period, but in P. glauca the concentration of all compounds were significantly lower in N-treated thalli compared with those that got only rainwater. The results are consistent with a high degree of constitutive defence in three of four species, and we conclude that all the investigated lichens seem to have rather robust chemical defence systems despite considerable manipulation of the environmental conditions.