Strategies of attack and defence in woody plant–Phytophthora interactions

This review comprises both well‐known and recently described Phytophthora species and concentrates on Phytophthora–woody plant interactions. First, comprehensive data on infection strategies are presented which were the basis for three models that explain invasion and spread of Phytophthora pathogens in different woody host plants. The first model describes infection of roots, the second concentrates on invasion of the trunk, and the last one summarizes infection and invasion of host plants via leaves. On the basis of morphological, physiological, biochemical and molecular data, scenarios are suggested which explain the sequences of reactions that occur in susceptible and tolerant plants following infections of roots or of stem bark. Particular emphasis is paid to the significance of Phytophthora elicitins for such host–pathogen interactions. The overall goal is to shed light on the sequences of pathogenesis to better understand how Phytophthora pathogens harm their host plants.     

A method for routine measurements of total sugar and starch content in woody plant tissues

Several extraction and measurement methods currently employed in the determination of total sugar and starch contents in plant tissues were investigated with the view to streamline the process of total sugar and starch determination. Depending on the type and source of tissue, total sugar and starch contents estimated from samples extracted with 80% hot ethanol were significantly greater than from samples extracted with a methanol:chloroform:water solution. The residual ethanol did not interfere with the sugar and starch determination, rendering the removal of ethanol from samples unnecessary. The use of phenol-sulfuric acid with a phenol concentration of 2% provided a relatively simple and reliable colorimetric method to quantify the total soluble-sugar concentration. Performing parallel sugar assays with and without phenol was more useful for accounting for the interfering effects of other substances present in plant tissue than using chloroform. For starch determination, an enzyme mixture of 1000 U alpha-amylase and 5 U amyloglucosidase digested starch in plant tissue samples more rapidly and completely than previously recommended enzyme doses. Dilute sulfuric acid (0.005 N) was less suitable for starch digestion than enzymatic hydrolysis because the acid also broke down structural carbohydrates, resulting in overestimates of starch content. After the enzymatic digestion of starch, the glucose hydrolyzate obtained was measured with a peroxidase-glucose oxidase/o-dianisidine reagent; absorbance being read at 525 nm after the addition of sulfuric acid. With the help of this series of studies, we developed a refined and shortened method suitable for the rapid measurement of total sugar and starch contents in woody plant tissues.     

Diversity in the chemical composition and digestibility of leaves from fifty woody species in temperate areas

Agroforestry Systems - In temperate regions, tree leaves could be a source of energy, protein, vitamins and minerals for ruminants. Our objective was to study the diversity in chemical composition...     

Laccase isoenzyme patterns of European Armillaria species from culture filtrates and infected woody plant tissues

Polyacrylamide isoelectric focusing with specific staining for laccase activity was used to characterize laccase from European Armillaria species (Armillaria ostoyae, Armillaria mellea, Armillaria gallica, Armillaria cepistipes). The enzyme was extracted from culture media either supplemented, or not, with pine sawdust, and also from Pinus pinaster naturally infected by A. ostoyae, or artificially inoculated with A. mellea and A. ostoyae. Some differences in banding patterns were found for Armillana isolates according to the species and the culture media, but a common band at pI = 3.4 was found in all the extracts tested, independently of their origin (culture filtrate or wood).     

Douglas-fir and western larch: chemical and physical properties in relation to Douglas-fir bark beetle attack

Frequency of Douglas-fir bark beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), attack on western larch (Lark occidentalis Nutt.) was negatively correlated with 3-carene content of the xylem oleoresin. Concentrations of all oleoresin volatiles from stem cores of standing trees were higher in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) than in western larch with the single exception of 3-carene. Successful brood production by the Douglas-fir bark beetle in standing trees of Douglas-fir but not western larch may therefore be explained, at least in part, by the high 3-carene content of western larch. Other differences between the species that might affect susceptibility to beetle attack include thinner phloem, higher phloem moisture content and larger diameter vertical resin ducts in western larch compared with Douglas-fir. Live standing western larch had no oleoresin exudation pressure, suggesting that this trait is not associated with resistance to attack by the Douglas-fir bark beetle in this species.     

Forest structure and woody plant species composition after a wildfire in beech forests in the north of Iran

Beech (Fagus orientalis Lipsky) forest covers about 565,000 ha of land in Guilan province, north of Iran and forms a major carbon pool. It is an important economic, soil protection and recreation resource. We studied long-term effects of fire on the structure and composition 37 years after fire occurrence in these forests. To do this research, we selected 85 ha burned and 85 ha unburned beech forests). The results indicated that the fire had not changed the overall uneven-aged structure, but it changed forest composition from pure stands to mixed stands that now include species such as Carpinus betulus, Acer cappadocicum and Alnus subcordata. The density of trees and regeneration was significantly increased, while the density of shrubs significantly decreased. The main reasons for increased tree regeneration were attributed to (1) reduction of litter depth, and (2) increase in available light from opening of the canopy and reduction in shrub competition. It is apparent that the forest is on a path to return to its natural state before the fire after 37 years.     

木质素生物合成影响因素及基因调控

对木质素生物合成的影响因素及基因工程在调控木质素生物合成中的作用等进行了综述,提出了存在的问题,对进一步利用这些影响因素和基因工程手段对木质素含量和结构上的改良进行了展望.     

木质素和聚糖的酶催化交联产物在纤维板中的应用

利用木质素前驱物协同果胶在漆酶体系作用下处理麦草纤维,以湿法工艺制造高强度中密度纤维板.实验结果表明:经处理后,纤维板的24 h吸水厚度膨胀率(TS),纤维板的内结合强度(IB),静曲强度(MOR),弹性模量(MOE)分别达到16.7％,0 6MPa,25.1MPa,2 500 MPa.各项物理性能指标均达到或超过国家...     

Establishment patterns of woody species in low intensity-grazed pastures after the cessation of intensive agricultural use

Low intensity grazing with large herbivores is increasingly used to steer the development of mosaic landscapes (including wood-pastures) and woodland expansion on former agricultural land. We studied the establishment and early growth pattern of woody species in grasslands (formerly used for high intensity summer cattle grazing) in which a low intensity-grazing regime was set up between 4 and 11 years ago. We tested whether the developing vegetation patches, consisting of tall herbs and scrub, influenced this pattern. Further, we investigated if increased susceptibility to trampling disturbance by large herbivores on wet soils in floodplains influenced sapling establishment.Formerly intensively used grasslands were studied at six sites, four in floodplains and two in interfluvial zones on nutrient rich, heavy soils. In total, we sampled 141 plots with grassland, tall herb or scrub vegetation and recorded individuals of established tree and shrub species, their height, diameter, browsing damage and distance to potential seed sources. In the floodplains, we recorded soil disturbance by large herbivores (hoofprints) in wet and moist soils.Sapling frequencies, with Fraxinus excelsior as the most common species (>50% of all individuals), were two to three times higher in tall herb and scrub patches compared to grassland. Only the spiny Crataegus monogyna established in higher frequencies in grassland plots. In floodplains, we found two to three times more established woody saplings in wet tall herb plots, compared to moist and wet grassland plots and moist tall herb plots.Browsing reduced sapling height in grassland and tall herb patches. Only in scrub patches did average height (±2.5 m) reach above the browse line. We found 30–70% less browsing damage to saplings in scrub compared to damage in grassland and tall herb plots. In particular, damage to the apical shoot was strongly reduced.Our findings show that tree establishment occurs in spatial association with non-grassland patches that offer protection against browsing. Fast growing spiny shrubs like Rubus sp. offer protection for palatable saplings, allowing establishment and growing out beyond the browse line. Alternatively, increased establishment occurs in wet tall herb patches, where soil disturbance by moderate trampling favours germination and, subsequently, saplings are protected at least temporarily against browsing by unpalatable tall herbs.     

Impact of the pinewood nematode, Bursaphelenchus xylophilus, on gross calorific value and chemical composition of Pinus pinaster woody biomass

The pinewood nematode (PWN), Bursaphelenchus xylophilus, the causal agent of the pine wilt disease, has been detected in several regions of Portugal affecting Pinus pinaster, a coniferous species of a great economic value. The nematodes, migrating through resin canals and feeding on parenchyma cells, induce rapid metabolic changes in ray parenchyma cells, cavitation areas, and denaturation and necrosis of parenchyma and cambial cells. To understand how anatomic changes and biochemical incidences of tree defense reactions affect the technological parameters of the wood, the gross calorific value (GCV) and chemical composition of PWN-infected and -uninfected P. pinaster wood were evaluated. The GCV was determined using Parr 6300 Automatic Isoperibol Calorimeter, and chemical composition analysis was performed by determining the contents of carbon, hydrogen, nitrogen, sulfur and Ash on complete and instant oxidation of samples by “flash” combustion. The Student’s t test with Welch correction was used for statistical data analysis. The difference between the GCV and chemical composition for PWN-infected and -uninfected P. pinaster wood was statistically significant for the GCV and for hydrogen and nitrogen contents. The carbon, oxygen, sulfur and Ash contents did not differ statistically. The GCV of PWN-infected wood varied between the highest value of hardwood and the lowest value of softwood. This interdisciplinary study stresses the important technological and economic aspects, namely the impact of PWN on wood properties and the suitability of infected P. pinaster wood for use in the wood-processing and energy industries.     

木本植物重金属毒害及抗性机理

主要从重金属对木本植物毒害作用和木本植物对重金属的抗性机理方面,综述了国内外在该领域的研究进展,并分析了现阶段在研究重金属对木本植物的毒害和木本植物对重金属的抗性机理方面存在的问题,提出了今后的研究趋势。     

我国木本粮油产业发展战略研究

木本粮油产业是以栽培利用木本淀粉类和木本油料类经济树种的产业门类。阐述了我国发展木本粮油产业的战略意义——发展木本粮油产业是缓解我国粮油供需矛盾、维护国家粮油安全的必然选择,是发展绿色经济、促进农民增收的重要途径,是优化食物结构、提高人民生活水平的现实需要,是加快国土绿化、改善生态环境的有效方式;分析了我国发展木本粮油产业的有利条件——我国有非常丰富的木本粮油树种资源,有适宜发展木本粮油的大面积丘陵山地,有广阔的国内外消费市场;提出了我国发展木本粮油产业的对策和建议——应该把发展木本粮油产业纳入国家粮食安全、食用油安全和能源安全的全新发展轨道中,要加大政府扶持力度,加大科技支撑力度,科学制订木本粮油产业规划,实施木本粮油产业的集约化栽培,延长产业链条,提高综合效益,提高木本粮油产业化技术水平,加强人才培养,保障产业发展的技术力量。     

朝阳市木本植物资源的保护与开发利用

文章对朝阳市森林植被的演变、分布状况、分异规律进行了论述。为更加科学、合理地保护与开发利用木本植物资源,对各树种的利用价值按功能分项归类,分别划入生态防护、用材、经济、园林绿化、蜜源植物、纯天然绿色食品、代茶饮料、饲料、工业原料、中药材等,对开发利用这些资源提出了新的见解。     

Windthrow and recruitment of large woody debris in riparian stands

To document the impacts of windthrow in riparian leave strips and identify the components needed for small stream large woody debris (LWD) recruitment modeling, we monitored nine small streams at a temperate rainforest site in coastal British Columbia. This study was a component of a larger integrated study of forest management impacts on small streams. A series of small clearcuts were harvested in 1998 in a 70-year-old second growth stand that had regenerated naturally following logging and wildfire. Three cutblocks each were assigned to 10 m and 30 m buffer width treatments and three areas were assigned as unharvested controls. Seven years after the 1998 logging, all logs greater than 10 cm diameter that spanned at least part of stream channel width were measured. A total of 179 logs were recorded. Post-harvest windthrow was higher in the 10 m buffer treatment, while competition-related standing tree mortality was higher in the controls. The major windthrow events had occurred in the first and second years after logging of adjacent stands. There was no significant difference in the number of spanning and in-stream logs in the 10 m, 30 m buffer and control treatments. More than 90% of the LWD was in the 10–30 cm diameter classes. The majority of logs were oriented perpendicular to the stream channel. At the time of measurement, the majority of these trees were still suspended above the stream channel, indicating that the recruitment of logs into the stream channel is a long-term process. Time to recruitment into the channel is dependent on log and valley geometry, log size, species, and log condition prior to toppling. Log height above stream was negatively correlated with log decay class and valley width. Log length was negatively correlated with state of decay, and many windthrown logs were in an advanced state of decay before they entered the stream.     

木质素生物合成及其基因调控的研究进展

木质素是地球上数量仅次于纤维素的有机物, 在植物生长发育中具有重要的生物学功能, 也是生物质能源的来源之一, 但在制浆造纸过程中, 将木材原料中木质素与纤维素分离, 不仅能耗高, 成本高, 而且废弃物还污染环境.林木木质素改良对于提高纸浆得率和质量、降低造纸经济成本以及环境保护, 都具有重要意义.文中介绍了木质素生物合成途径及其基因调控的研究进展, 此外, 还介绍了木质素生物合成基因调控的研究趋势, 主要是木质素特异性启动子、双价和多基因结构的共抑制以及转录因子的调控.     

木本植物组织培养器官发生植株再生研究进展

综述了我国木本植物组织培养器官发生植株再生研究领域的研究现状，分别从影响木本植物器官发生的主要因子、生理生化基础、遗传变异性以及在基因转化中的应用等几个方面进行了评述，提出了该研究领域目前存在发展不平衡等问题。