细胞壁降解酶在落叶松-杨栅锈菌与寄主互作过程中的作用

对落叶松-杨栅锈菌入侵不同抗性寄主过程中的细胞壁降解酶活性进行测定,明确聚甲基半乳糖醛酸酶(PMG)、果胶甲基反式消除酶(PMTE)、羧甲基纤维素酶(CX)、β-葡萄糖苷酶(β-G)4种降解酶在该菌入侵中的作用.研究发现:抗病和感病组合中PMG均在接种后第2天和第5天出现2个活性高峰,在第5天时达到最大值.PMTE、CX和β-G活性分别第3、2和3天达到活性高峰,其中PMG和PMTE的活性高,而Cx和β-G的活性则相对较低.在感病组合内PMG、PMTE、CX、β-G活性较抗病组合大,表明这4种细胞壁降解酶对该菌入侵起一定的作用.     

不同水分条件下枣果实果皮细胞壁的变化特性

试验研究了不同水分条件下壶瓶枣果实发育过程中果皮细胞氧化性酶、细胞壁物质成分、细胞壁代谢相关酶活性的变化规律及其之间的关系。结果表明,在果实发育成熟期,枣果皮SOD,POD活性呈上升趋势,PPO活性呈先上升后下降的趋势。果皮细胞壁代谢相关成分离子结合型果胶、共价结合型果胶、半纤维素、纤维素的含量先上升后下降,水溶性果胶呈上升趋势。果皮细胞壁代谢相关水解酶多聚半乳糖醛酸酶、纤维素酶在果实发育期不断上升;果胶甲酯酶的活性在前期下降,后期变化不明显。喷灌处理的果皮氧化性酶和细胞壁代谢相关酶活性小于对照,离子结合型果胶、共价结合型果胶、半纤维素、纤维素的含量高于对照,水溶性果胶则相反。     

果实软化过程中细胞壁结构和组分及细胞壁酶的变化

概述了果实软化过程中细胞壁结构和组分及细胞壁酶的变化。多数果实软化是由于多聚半乳糖醛酸酶、纤维素酶、果胶甲酯酶和β-半乳糖苷酶等细胞壁酶降解细胞壁物质,使细胞壁结构和组分发生变化,进而引起果实软化。不同的研究结果提示果实软化也有其他因子参与,加强果实生理生化基础研究尤为重要。     

用于筛选植物PGIP的酵母双杂交PGase诱饵载体

对真菌抗性较强的植物能利用自身的多聚半乳糖醛酸酶抑制蛋白(po lyga lacturonase-inh ib iting prote in,PG IP)来抑制真菌分泌的、降解植物细胞壁的主要物质——多聚半乳糖醛酸酶(po lyga lacturonase,PG ase)的活性.目前,快速、有效的获取植物PG IP的方法是通过酵母双杂交技术来进行的,而这首先要获得真菌PG ase的酵母诱饵载体.以真菌——互格链格孢PG ase的cDNA的为基础,将其克隆到M ATCHM AKER L exA Tw o-Hybrid System的诱饵载体中,并将诱饵载体(pL exA-PG ase)成功转化酵母菌株EGY 478[p8op-lacZ],经检测无自激活作用,可直接用于快速、大量地筛选植物PG IP.     

香榧假种皮开裂过程中组织结构、细胞壁代谢的变化

【目的】研究香榧假种皮开裂过程中细胞壁代谢及结构的变化，为进一步探明假种皮的开裂机制和探寻促进假种皮开裂的措施提供理论依据。【方法】在种实的不同发育时期内，测定香榧假种皮的开裂率和硬度的变化，分析细胞壁组分及相关降解酶活性的变化，结合石蜡解剖结构的观察，揭示假种皮细胞壁代谢与结构变化在开裂过程中的作用；通过测定香榧种实乙烯释放率的变化，并利用外源乙烯利/乙烯作用抑制剂（1-甲基环丙烯，1-MCP）处理分析乙烯在假种皮开裂过程中的作用，探讨乙烯与假种皮开裂的关系。【结果】1）从134～154 DASP(DASP：突破种鳞后的天数)，香榧假种皮的开裂率增加了10倍，硬度降低了61%，假种皮厚度增加了43%；假种皮开裂时（154 DASP），假种皮中靠近内表皮层的树脂道细胞群与其相邻树脂道细胞群之间的薄壁细胞降解，呈分离状态，且中间薄壁细胞层与内表皮层之间存在明显的分离层。2）从134～154 DASP，假种皮的水溶性果胶（WSP）总体上呈增加趋势，而CDTA可溶性果胶（SSP）和Na2CO3可溶性果胶（CSP）则呈降低趋势，其相关降解酶果胶甲酯酶（PME）和多聚半乳糖醛酸酶（PG）活性均呈...     

3种白腐菌木质纤维素酶活性及酶相关基因的TRAP标记遗传多态性

【目的】木质纤维素是重要的可再生资源,白腐菌对降解木质纤维素具有特殊的优势。研究3种白腐菌的生物学特性、酶学活性以及菌种间的遗传多样性,系统分析3种白腐菌木质纤维素酶的表达与相关基因多态性的关系,为高产木质纤维素酶菌种选育提供理论基础,为白腐菌木材降解分子机制的研究提供科学依据。【方法】以云芝栓孔菌、火木层孔菌和松杉灵芝3种白腐菌为研究材料,测定在不同培养温度下固体培养基中菌落的生长速度和液体培养基中的生物量变化,利用比色法测量白腐菌5种木质纤维素酶活性,运用目标区域扩增多态性( TRAP)分子标记分析3种白腐菌的木质纤维素降解相关酶基因的多态性。【结果】在不同温度下(23,28℃),3种白腐菌在PDA固体培养基上的生长速度均为云芝栓孔菌＞火木层孔菌＞松杉灵芝,云芝栓孔菌和火木层孔菌在28℃的生长速度高于23℃,而松杉灵芝在23℃培养生长更快;液体培养基中云芝栓孔菌的生物量高于火木层孔菌和松杉灵芝。3种白腐菌木质素相关酶活性受木屑诱导显著提高,木质素酶活性最高的是漆酶,其次是木质素过氧化物酶,最低的是锰过氧化物酶;纤维素酶的表达在3种白腐菌中无显著差异,但外切纤维素酶活性明显高于内切纤维素酶活性,玉米秸秆为碳源诱导产生的纤维素酶活性明显高于木屑碳源样品。云芝栓孔菌更偏好于木质素酶的表达,而火木层孔菌和松杉灵芝则更偏好于纤维素酶的表达。TRAP分子标记扩增结果显示,木质素酶相关基因的6对引物共产生109条条带,多态性条带为79条,多态性百分比为72.47%;纤维素酶相关基因的11对引物共产生198条条带,多态性条带为140条,多态性百分率为70.70%。【结论】通过生长速度、生物量、木质纤维素酶活性的检测以及 TRAP 分子标记结果表明3种白腐菌在种间具有较高的遗传差异。3种白腐菌木质素酶活性的大小与其酶基因多态性之间没有明显的对应关系;3种白腐菌纤维素酶活性大致相同,其基因多态性也比较一致。     

同果实软化有关的酶类研究进展

果实软化一直是采后生理研究的重要内容,果实软化同纤维素酶、多半乳糖醛酸酶、果胶甲酯酶和β-半乳糖苷酶的活性变化密切相关。该文综述了同果实软化有关的酶类在果实成熟衰老和软化过程中的变化规律,为控制果实采后软化提供理论依据。     

青枯菌胞外酶对木麻黄的致病作用研究

对三个致病性不同的木麻黄青枯菌Ｐｓｅｕｄｏｍｏｎａｓ ｓｏｌａｎａｃｅａｒｕｍ Ｅ．Ｆ．Ｓｍｉｔｈ产生的胞外酶活性测定显示,聚半乳糖醛酸酶（果胶酶）在活性在各菌之间无明显差别,但纤维素酶活性差别明显,并随菌株的致病性上升而增加,菌株致病性与酶活性具有高度正相关。     

桃果实采后软化机理研究进展

呼吸跃变型果实成熟时最显著的变化特征就是果肉的软化。桃是呼吸跃变型果实 ,其成熟季节气温较高 ,果实采后迅速进入呼吸高峰期 ,并快速软化。从而使其大规模的商业贮藏极其困难。所以有关桃果实成熟软化的影响因素及其调控 ,长期以来一直为采后生理工作者所关注。1　水解酶类　　大量研究表明 ,果实的软化主要是由于果实细胞壁成分被相应的水解酶降解。果实细胞壁组分复杂 ,所以与果实软化相关的水解酶种类也很多。目前有关果实软化水解酶的研究主要集中于多聚半乳糖醛酸酶 (ＰＧ)、果胶甲酯酶 (ＰＥ)和纤维素酶 (ＣＸ)。最近出现了 β -…     

人参锈腐病菌产孢条件研究

为了探明人参锈腐病菌Cylindrocarpon destructans(Zinss) Scholten的产孢条件,在室内不同培养条件下对人参锈腐病菌产孢条件进行了研究.结果表明,病菌分生孢子产生的适宜温度为15～ 25℃;厚垣孢子产生的适宜温度为10～20℃,最适为15℃.产生分生孢子和厚垣孢子的适宜pH值为5～7,最适pH值为6.不同碳源上病菌均能产生分生孢子和厚垣孢子,其中葡萄糖和果糖对分生孢子的产生促进最大,但不同的碳源对厚垣孢子产量的影响不明显.分生孢子在尿素为氮源的培养基上大量产生,在缺氮培养基上不产生;厚垣孢子在不同氮源培养基上均能产生,在酵母膏培养基上产量最大.不同培养基中,在人参根培养基上分生孢子产生所需时间短,产量高;厚垣孢子在PDA和基础培养基上产生所需时间短,产量高.光照条件对分生孢子的产生没有明显的影响,但对厚垣孢子的产生有明显的抑制作用.     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.