大孔吸附树脂提取甜茶苷的研究

从6种大孔树脂中筛选了适宜的提取分离甜茶苷的吸附剂,研究了大孔吸附树脂提取甜茶苷的工艺,包括甜茶苷溶液的质量浓度、pH值和流速对吸附过程的影响,解吸荆及解吸温度对解吸过程的影响。结果表明：AB-8树脂是理想的甜茶苷吸附剂,其吸附甜茶苷较理想的工艺条件是：原料液质量浓度约为7．7ms／L,pH值约为8,流速为3BV／h（BV为层析柱中树脂床的体积）;理想的洗脱条件为：流速为3BV／h,室温下以70％乙醇溶液为洗脱剂,用量为5BV,或40℃下,以60％乙醇溶液为洗脱剂,用量为4BV。实验室利用该工艺成功地分离出甜茶苷。     

大孔吸附树脂对蓝莓花色苷的分离工艺

以蓝莓果提取液为原料,研究了12种大孔树脂对花色苷的静态吸附与解吸效果,对比了5种对花色苷分离效果较优树脂的静态等温吸附曲线,优化了最优树脂分离纯化蓝莓花色苷的工艺技术参数。研究结果表明XDA-7最适用于蓝莓花色苷的分离纯化,最佳吸附工艺是:室温条件下,蓝莓提取液pH值3.0、质量浓度0.94 g/L、流速30 mL/h,最大吸附量15.41 g/L(湿树脂);最佳洗脱工艺是:室温条件下,80%甲醇、pH值3.0、流速60 mL/h、洗脱剂量75 mL,解吸率达92.65%。在该工艺参数下,经XDA-7树脂纯化冷冻干燥所得产品为紫黑色粉末,花色苷纯度由2.20%提高到24.54%,花色苷得率为70.2%,产品色价为121。     

栗壳天然食用色素纯化工艺的研究

为纯化栗壳色素,研究D-4020型大孔吸附树脂纯化栗壳色素的工艺条件,结果表明：当上样液pH值为5、质量浓度为0.20 mg/mL,吸附流速1.0 mL/min,静态吸附180 min,用80%乙醇作为解吸剂,解吸流速为0.5 mL/min,3.0 BV的解吸剂时,栗壳色素即可解吸完全。     

杜仲叶中绿原酸的提取方法与精制工艺研究

对杜仲(Eucommia ulmoides)叶片中绿原酸的提取与精制工艺进行研究,比较了酸水提取、40%乙醇提取以及纤维素酶提取对绿原酸提取效果的影响,结果表明,酶提取更有利于后续工艺对绿原酸的精制。通过静态吸附试验,比较HPD-100A、AB-8、HPD-400A、DM-130、HPD-600、HPD-826六种大孔吸附树脂对绿原酸的吸附及脱附性能,筛选出性能较好的HPD-826树脂进行动态试验,结果表明,该树脂在室温下对杜仲叶中绿原酸的动态吸附-脱附最佳工艺参数为:上柱液p H值3.0,上柱流速2 BV/h,上柱体积7 BV;脱附剂为60%乙醇,洗脱流速1BV/h,洗脱剂用量为2 BV。用优化后的工艺进行试验,所得绿原酸粗产品的纯度可达49.85%,且工艺具有良好的稳定性。     

大孔吸附树脂分离纯化山楂叶总黄酮的研究

比较了6种大孔吸附树脂ADS-5、ADS-8、ADS-17、NKA-9、D-101和AB-8对山楂叶总黄酮的吸附及脱附性能。在研究静态吸附的基础上,筛选出效果较好的树脂进行动态实验研究。实验结果表明:最佳分离纯化山楂叶总黄酮的树脂为D-101。该树脂室温下对山楂叶总黄酮动态吸附-脱附较优的工艺参数为:上柱液pH值4.5~5.5;上柱速度2 BV/h,溶液处理量6 BV/次;洗脱剂为70%乙醇,脱附剂的流速1 BV/h,脱附剂用量2 BV/次。     

均匀设计法优选大孔树脂纯化七叶莲总皂苷工艺研究

以总皂苷比吸附量和解吸率为指标,通过静态和动态吸附解吸附试验,从9种树脂中筛选出AB-8型大孔吸附树脂;以总皂苷收率和总皂苷纯度为指标,通过单因素试验考察了最佳洗脱剂浓度,并利用均匀设计法对大孔树脂富集纯化的工艺进行了优化.结果表明:以70%乙醇为洗脱剂,以总皂苷收率为指标,优选的工艺参数为:上样质量浓度0.976g/L、上样流速2.2mL/min、洗脱剂用量3.0BV(1BV=80mL,下同)、洗脱流速3.6mL/min,其总皂苷收率62.17%,总皂苷纯度41.22%;以总皂苷纯度为指标,优化的工艺参数为:上样质量浓度0.976g/L、上样流速2.8mL/min、洗脱剂用量0.6BV、洗脱流速0.8mL/min,其总皂苷收率41.25%,总皂苷纯度49.79%.     

大孔吸附树脂纯化常春藤皂苷C工艺研究

通过静态吸附试验比较7种树脂对常春藤皂苷C的吸附与解吸,筛选出效果最佳树脂,通过动态吸附试验对最佳树脂的上样p H、上样体积、洗脱液浓度、洗脱体积、洗脱流速进行优化。结果表明:HPD-100树脂对常春藤皂苷C的吸附与解吸性能最好,HPD-100树脂对常春藤皂苷C纯化的最佳条件为:上样体积为6BV,洗脱液乙醇浓度为80%,洗脱体积为7 BV,洗脱流速为1 BV/h。     

AB-8大孔吸附树脂对树莓红色素纯化工艺的研究

研究了AB-8大孔吸附树脂纯化树莓红色素的最佳工艺条件。结果表明:在洗脱液为pH=2的95%乙醇、吸附流速为1.0BV/h、洗脱流速为0.5 BV/h条件下,分离纯化出的色素含量最大,因此为最佳的工艺条件。     

大孔树脂纯化皱皮柑果皮黄酮工艺研究

以皱皮柑果皮为材料,筛选出对皱皮柑果皮黄酮吸附和解吸性能好的大孔树脂,并探讨大孔树脂纯化皱皮柑果皮黄酮的工艺条件。结果表明:弱极性的AB-8大孔树脂对皱皮柑果皮黄酮的吸附和解吸效果较好。AB-8大孔树脂纯化皱皮柑果皮黄酮的最佳工艺条件为:以50%乙醇作为洗脱剂,洗脱剂流速1.5 BV/h,洗脱剂用量为3倍柱床体积。纯化后皱皮柑果皮黄酮纯度可达到15.45%。     

笃斯越桔花色苷纯化工艺的研究

比较6种大孔树脂对笃斯越桔花色苷的吸附和解吸效果,筛选适合笃斯越桔分离纯化的树脂类型,并对其吸附性能进行研究,获得适合的树脂及动态吸附和解吸的最佳条件。研究结果表明:AB-8大孔树脂为越桔花色苷吸附和解吸效果最佳的树脂类型;花色苷粗提物用pH值为3的缓冲液配制、上样流速为1.0 mL/min、上样浓度为1.5 mg/mL、上样体积为400 mL,采用90 mL的60%乙醇溶液以1.0 mL/min的流速进行花色苷解吸,效果较好。     

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.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

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.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.