离体毛竹笋纤维素和木质素含量及POD和PAL活性研究

研究了离体后毛竹笋纤维素、木质素含量以及苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)活性的变化.结果显示:笋体纤维素、木质素含量从笋尖到笋基部逐渐增加;PAL、POD活性笋尖明显高于笋基部.离体后贮藏的竹笋纤维素、木质素含量随贮藏时间的延长而增加,在前5 d纤维素的增加速度极快,在后5 d增加速度明显趋缓,但木质素含量随贮藏时间的延长基本呈匀速态势增加;POD、PAL活性随贮藏时间的延长,活性均显著增加.对离体竹笋进行低温处理(4 ℃)可显著降低竹笋的PAL、POD活性,减少木质素和纤维素合成,低温对纤维素的影响高于木质素.     

竹笋采后涂膜保鲜对其木质化的影响

为了给竹笋采后保鲜和竹笋膳食纤维的加工提供理论指导,将采回的毛竹春笋的不同部位在3℃冷藏条件下,进行壳聚糖涂膜保鲜对竹笋中苯丙氨酸解氨酶（PAL）和过氧化物酶（POD）活性以及纤维素和木质素含量影响的研究.结果表明：从顶部到基部,竹笋各区段部位PAL和POD活性逐渐增强,纤维素和木质素含量增大;与对照相比,各种涂膜保鲜处理均显著降低竹笋的PAL和POD活性及纤维素和木质素的生成,加入亚硫酸钠能延缓竹笋的木质化进程.     

保鲜处理对高节竹笋采后生理的影响

采用壳聚糖的3种保鲜处理方法对高节竹笋进行了试验比较,测定了高节竹笋采收后在贮藏过程中与竹笋老化密切相关的苯丙氨酸解氨酶(PAL)和过氧化物酶(POD)的活性,以及纤维素和木质素含量.结果表明:竹笋采收后,随着贮藏时间的增加,PAL和POD活性在短时间内快速地增加,经过一定时间后减少,纤维素和木质素含量随竹笋的老化过程而增加.以壳聚糖涂膜和BCY保鲜剂共同作用的保鲜处理在7 d内各指标的增加速度最慢,保鲜效果最佳.     

雷竹笋采后贮藏生理的研究

研究了雷竹笋采后在常温 (2 5℃ )贮藏期间的相对含水量、粗蛋白质含量、过氧化物酶 (POD)活性、苯丙氨酸解氨酶 (PAL)活性、木质素含量的相互关系和变化规律 ,结果表明 ,相对含水量和蛋白质含量呈下降趋势 ,POD、PAL等酶活性呈先上升后下降趋势 ,木质素含量不断增加。POD、PAL酶活性的提高与笋体内木质素的增加密切相关     

甜龙竹笋采后不同时间及温度储藏下酶活性的变化

以甜龙竹笋为研究材料,采用植物ELISA检测试剂盒测定不同储藏时间(0、12、24、36、48、60、72 h)和不同储藏温度(0℃、4℃、常温对照)下PAL(苯丙氨酸解氨酶)、PPO(多酚氧化酶)、CAT(过氧化氢酶)、POD(过氧化物酶)、CAD(肉桂醇脱氢酶)的变化特征。结果表明:在常温(20~25℃)下,PAL活性呈现先上升后下降的趋势,POD、PPO、CAT、CAD呈现波动变化趋势;其次,4℃以下对PAL、POD、PPO、CAD活性存在抑制作用,对CAT活性影响不大。0℃、4℃储藏对采后甜龙竹笋酶活性有降低作用,可通过低温结合其他方法对甜龙竹笋进行保鲜处理,达到延缓甜龙竹笋老化的目的。     

褪黑素处理对高节竹笋低温贮藏过程中木质化的影响

【目的】探讨褪黑素处理条件下,高节竹笋采后低温(4℃)贮藏过程中木质素形成、抗氧化酶活性、转录因子基因表达的变化模式,为阐明褪黑素处理对竹笋采后木质化过程的影响及其调控机制提供参考。【方法】以高节竹笋为试验材料,分析低温(4℃)贮藏过程中(0、3、6、9、12天)褪黑素(1. 0 mmol·L-1)处理组和对照组竹笋硬度、黄度、亮度,木质素、纤维素含量,木质素合成相关的苯丙氨酸裂解酶(PAL)、过氧化物酶(POD)活性,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸还原酶(APX)活性以及NAC、MYB转录因子基因表达等指标。【结果】与对照相比,外源褪黑素处理减缓笋体变硬和黄化的速度以及木质素和纤维素的积累速度,显著抑制PAL和POD活性,提高了SOD、CAT和APX活性,有效延缓高节竹笋木质化的发生进程;转录因子MYB20、MYB63、MYB85、SND2和VND7的表达随竹笋采后贮藏时间的延长均受到不同程度的诱导,而MYB42、MYB43、NST1和KNAST7的表达量则有所下降。褪黑素处理一定程度上抑制了MYB20、MYB42和KNAT7的表达,促进了MYB43、MYB63、MYB85和SND2的表达。【结论】外源褪黑素处理有效延缓了高节竹笋采后低温贮藏过程中木质化的发生进程,其机制可能是褪黑素处理降低了木质素生物合成相关酶的活性,提高了抗氧化能力。此外,褪黑素也可能参与竹笋木质化的转录调控过程。     

毛竹笋在快速生长期的木质化调控网络

木本竹因其优质材性而成为传统木材良好的替代品。木质化程度和木质素含量影响着木材材性，然而单子叶植物的木质化调控网络尚不清楚。为了阐明毛竹（Phyllostachys edulis）木质化的分子调控机制，利用转录组、miRNA和降解组测序，并结合实验对竹笋进行综合分析研究。结果表明：木质化程度和木质素含量随笋高度的增加而增加，而苯丙氨酸解氨酶（PAL）和漆酶（LAC）活性则随笋高度的增加表现为先升高后降低。在不同高度笋的代表性节间（第13节）的不同部位中共鉴定了11 504个差异表达基因（DEG），其中与细胞壁和木质素生物合成相关的大部分DEG表达随笋高度上调，而与细胞生长相关的一些DEG表达则下调。通过miRNA测序鉴定出1 502个miRNA，包括已知的1 223个和新鉴定的279个。通过生物信息学预测和降解组分析，共鉴定出691个差异表达的miRNA，共靶向5 756个差异表达基因。据此构建了毛竹笋木质化调控网络，包括11个miRNA、22个转录因子和36个酶基因。另外，根据过表达PeLAC20转基因拟南芥中木质素含量显著增加，提出了一个miRNA介导的‘MYB-PeLAC20’的木质素单体聚合调控模型。研究结果不仅对解析竹子木质素生物合成的调控分子机制具有重要科学价值，而且对理解其他单子叶植物的相关机制具有重要参考价值，有助于制定竹材材性改良策略。     

茶多酚处理对采后勃氏甜龙竹笋木质化的影响

为探索生物保鲜剂处理对采后勃氏甜龙竹笋木质化的影响,以采后勃氏甜龙竹笋为研究材料,剥壳鲜笋用不同浓度茶多酚溶液(0.5％、1.5％、2.5％)处理,并用聚乙烯保鲜袋包装,在4℃下进行贮藏,分析0、2、4、6、8 d贮藏期内,处理组和不添加茶多酚对照组的色差值、木质素、粗纤维、还原糖含量,以及苯丙氨酸解氨酶(PAL)、多...     

松材线虫侵染对马尾松苯丙烷类代谢的影响

1.5年生马尾松植株接种松材线虫后,苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)、多酚氧化酶(PPO)的活性水平均高于对照,活性高峰通常出现在症状表现前夕,并在植株发病后下降.叶内PAL和POD活性高峰的出现晚于茎,与叶部病害发展一致.茎中酚类物质的含量随着线虫侵染时间的延长逐渐增加,至发病时达到高峰.酚类物质含量的变化与PAL、POD、PPO 3种酶活性的变化趋势基本一致.松材线虫的侵染明显影响寄主植物的苯丙烷类代谢,由此可知,松材线虫病的发生发展与松材线虫诱导感病寄主苯丙烷类代谢的异常变化有关.     

锥栗对栗疫病的抗性与苯丙氨酸解氨酶的关系

健康的锥栗(Castanea henryi)皮层中,苯丙氨酸解氨酶(PAL)比活力与抗感病性之间不相关.不同抗病性的锥栗品种接种栗疫菌(Cryphonectria parastttca)后,PAL比活力均上升,接种144 h后,PAL比活力抗病性强的品种比抗病性弱的品种高.接种前以及接种后的各个时间内,木质素含量都是抗病品种比感病品种高.绿原酸的含量与品种的抗病性之间不呈规律性的相关,从绿原酸对栗疫菌菌丝生长影响的测定结果可知,锥栗体内的绿原酸浓度不足以影响栗疫菌.可见,接种后的皮层PAL比活力以及接种前、后的皮层木质素含量可作为衡量锥栗抗病性强弱的指标.     

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

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。