西南桦花粉离体萌发的适宜条件与萌发特征

应用各种浓度蔗糖、蔗糖 硼酸培养基于系列温度下开展西南桦花粉萌发对比试验,研究了蔗糖、硼酸浓度对西南桦花粉离体萌发的影响,筛选出适合西南桦花粉萌发培养基的适宜组分和适宜培养温度,并应用4个单株的花粉对其萌发特征进行了初步研究.结果表明:蔗糖基本培养基上添加硼酸能够显著促进西南桦花粉萌发;西南桦花粉离体萌发的合适培养基为15%蔗糖 200 mg·kg-1硼酸,适宜培养温度为30℃;在此条件下培养3 h后花粉萌发率基本稳定,培养7 h后花粉管长度也趋于稳定.     

大叶相思花粉离体萌发适宜条件及活力检测方法

【目的】对大叶相思花粉离体萌发适宜条件以及花粉活力不同检测方法进行研究,为今后进一步开展人工控制授粉、选育优良的马大杂交新品种提供基础。【方法】采回花穗的次日10:00之后,使用毛笔刷法收集大叶相思花粉;通过不同培养温度、不同蔗糖浓度和不同硼酸浓度处理后进行花粉离体萌发,筛选适宜大叶相思花粉离体萌发的条件;采用过氧化物酶法、I_2-KI法以及花粉管离体萌发法对大叶相思花粉进行活力测定,探讨大叶相思花粉有效的活力测定方法。【结果】大叶相思花粉在28℃下培养,其花粉平均萌发率为71.99%,花粉管平均长度为5.3 D(1 D=1倍的花粉粒长度),花粉管平均条数为6.2条,显著高于其他培养温度的处理。当培养基中含有200 g·L~(-1)蔗糖时,大叶相思花粉萌发率为84.96%,其花粉管平均长度为5.8 D,花粉管平均条数为6.2条,显著高于含有其他蔗糖浓度的处理。在含有300 mg·L~(-1)硼酸的培养基中培养大叶相思花粉,其平均萌发率为75.32%,花粉管平均长度可达4.8 D,平均花粉管条数为5.4条,显著高于在其他硼酸浓度下的处理。大叶相思花粉在培养温度30℃、200 g·L~(-1)蔗糖、300 mg·L~(-1)硼酸的培养基中萌发率为98.26%,花粉管长度均可达到10倍复合花粉粒的长度,最多可萌发出10条花粉管,显著高于其他处理。培养3 h的大叶相思花粉,萌发率为65.74%;培养6 h时,其萌发率为90.55%;培养24 h后,其萌发率趋于稳定,达到最高值98.26%。过氧化物酶法检测的花粉活力为99.67%,I_2-KI法检测的花粉活力为99.00%,花粉管离体培养法检测的花粉活力为98.15%,3种方法检测的花粉活力无显著差异。【结论】大叶相思花粉在不同的离体培养处理下,其萌发情况均不相同且差异显著,最佳离体萌发条件为200 g·L~(-1)蔗糖+300 mg·L~(-1)硼酸,培养温度为30℃,萌发率为98.26%。过氧化物酶法、I_2-KI法以及花粉管离体培养法检测的花粉活力无显著差异。研究结果可为今后开展大叶相思的花粉收集、贮藏及活力测定等研究,以及开展人工控制授粉选育优良马大杂种相思新品种等研究提供重要依据。     

牛角瓜花粉离体萌发研究

为了探讨牛角瓜花粉离体萌发的最适条件及培养基成分,以2年生牛角瓜新鲜花粉为试材,研究了不同溶液对牛角瓜花粉块壁解离效果的影响情况;还采用离体培养法,研究了不同培养温度和培养时间、不同培养基组分对牛角瓜花粉萌发率和花粉管生长的影响情况。结果显示:以10%的Na OH溶液将牛角瓜花粉块处理10 min的解离效果最好;牛角瓜花粉离体萌发的最适温度为30℃,在此温度条件下培养6 h后其花粉萌发率基本稳定,培养12 h后其花粉管生长最好;蔗糖对牛角瓜花粉萌发率及花粉管长度的影响均较大,硼酸对花粉萌发率及花粉管长度的影响均较小;牛角瓜花粉萌发和花粉管生长的最适培养基为20%蔗糖+0.1%硼酸+5 mg/L氯化钙+15 mg/L 6-BA,在此培养基上并在30℃的温度条件下培养6 h,其花粉萌发率达到94.77%,花粉管长度为11.07 mm。     

日本海棠花粉最佳离体萌发培养基筛选及萌发过程研究

为给观赏海棠杂交育种提供参考依据,采用单因素和正交试验方法,对日本海棠花粉离体萌发培养基进行了筛选,对其花粉活力展开了研究,探讨并观察了观赏海棠花粉离体萌发条件和花粉萌发过程。单因素试验结果表明:当蔗糖、硼酸、硝酸钙的处理浓度分别为10%、0.02%(其萌发率与0.04%浓度处理的无显著差异)、0.02%(其萌发率与0.01%浓度处理的无显著差异)时,日本海棠的平均花粉萌发率及花粉管长度最高值分别达到55.2%与853.11μm、54.4%与595.07μm、37.6%与713.74μm,显著高于同一试验因素下的其余各处理。正交试验结果表明:10%蔗糖+0.02%硼酸+0.04%硝酸钙的组合培养基为日本海棠离体萌发的最适培养基,以此培养基培养的日本海棠其平均花粉萌发率与花粉管长度分别达到70.1%和777.02μm,显著高于除以(10%蔗糖+0.01%硼酸+0.03%硝酸钙)组合培养基处理以外的其他组合培养基处理。在日本海棠花粉离体萌发过程中,培养第1个小时内花粉未萌发,培养2~4 h的花粉萌发率和花粉管生长速率均达到最高值,分别达23.4%/h及259.01μm/h,培养8 h后,其萌发速率趋于平稳,培养12 h后,其花粉管生长速度趋于平稳。研究结果表明,日本海棠离体萌发的最佳培养基为(10%蔗糖+0.02%硼酸+0.04%硝酸钙)组合培养基,以此组合培养基培养2~4 h其花粉萌发率与花粉管生长速率均最高。     

影响杂交榛花粉萌发和花粉管生长的培养基组分研究

采用固体培养基研究了不同浓度的蔗糖、硼和钙配比对杂交榛花粉萌发及花粉管生长的影响.结果表明:蔗糖、硼酸浓度间对花粉萌发有显著影响,钙浓度间对花粉萌发的促进作用不明显;蔗糖150 g·L~(-1)、硼酸100 mg·L~(-1)时最适宜花粉管伸长;蔗糖的缺乏会导致胼胝质在花粉管顶端积累,使其生长停滞,缺硼时胼胝质在花粉管内分布正常.杂交榛花粉适宜的培养基为:蔗糖150 g·L~(-1)+硼酸100 mg·L~(-1)氯化钙100 mg·L~(-1)琼脂10 g·L~(-1).     

七子花花粉萌发的研究

设置8种不同的培养基进行七子花花粉萌发的研究.结果表明,不同培养基中七子花的花粉萌发率、花粉管破损率和花粉净萌发率有较大的差异.硼酸对七子花花粉萌发有明显的促进作用,但也会增加花粉管的破损率.以0.5mg/L 2,4-D、10%蔗糖、0.5%琼脂作为培养基,七子花花粉萌发率最高,达84.90%;以10mg/L H3BO3、0.5mg/LNAA、10%蔗糖、0.5%琼脂作为培养基,七子花花粉的净萌发率最高,达53.25%.硼酸与NAA或Ca(NO3)2配合使用,有利于七子花的花粉萌发和花粉管的发育.     

不同质量浓度的蔗糖和硼酸对北京杨花粉萌发的影响

以北京杨新鲜花粉为材料,研究固体培养基中蔗糖和硼酸不同质量浓度对花粉萌发的影响,结果表明:在培养基不含硼酸时,最适宜萌发的蔗糖质量浓度为10%,萌发率93.5%;当达到20%时,抑制花粉萌发,萌发率仅为55.6%。在培养基不含蔗糖时,最适宜萌发的硼酸质量浓度为0.01%,随着质量浓度升高,萌发率呈下降状态。在蔗糖和硼酸的双重作用下,最适宜萌发的质量浓度为10%蔗糖+0.01%硼酸,萌发率高达98.6%,花粉管生长快、健壮。新鲜花粉生活力测定的培养时间为24 h。     

3种悬钩子属植物花粉离体萌发培养基成分筛选

为了探究悬钩子属植物花粉离体萌发的最适培养基成分,选择3种悬钩子属植物:山莓、蓬藟、掌叶覆盆子,采用离体培养法,研究了不同培养基组分对悬钩子属花粉萌发率、萌发优秀率与花粉管长度的影响。结果表明:山莓花粉萌发率最高的培养基组合:琼脂1%+蔗糖17%+H_3BO_3 0.03%+CaCl_2 0.001%;山莓花粉萌发优秀率最高的培养基组合:琼脂1%+蔗糖17%+H_3BO_3 0.05%+CaCl_2 0.001%;山莓花粉管长度最长的培养基组合:琼脂1%+蔗糖15%+H_3BO_3 0.03%+CaCl_2 0.001%;蓬藟花粉萌发率与萌发优秀率最高的培养基组合:琼脂1%+蔗糖5%+H_3BO_3 0.01%+CaCl_2 0.000%,此条件下花粉管亦最长。掌叶覆盆子花粉萌发率与萌发优秀率最高的培养基组合:琼脂1%+蔗糖10%+H_3BO_3 0.01%+CaCl_2 0.000%;掌叶覆盆子花粉管长度最长的培养基组合:琼脂1%+蔗糖15%+H_3BO_3 0.01%+CaCl_2 0.000%。     

培养基成分对仁用杏花粉离体萌发的影响

为了研究培养基成分对仁用杏花粉离体萌发的影响,以仁用杏‘优一’为试材,以蔗糖、硼酸、二水合氯化钙、赤霉素为培养基的主要成分,通过单因素和正交试验,筛选出适宜‘优一’花粉萌发的培养基成分及浓度。结果表明,4种成分在一定浓度范围内对‘优一’花粉萌发起促进作用,高质量浓度则抑制,促进‘优一’花粉萌发较适宜的浓度分别为蔗糖15%,硼酸0.003 g·L-1,二水合氯化钙0.000 2 g·L-1,赤霉素0.000 8 g·L-1;赤霉素对‘优一’花粉管伸长作用明显,其花粉管生长量、长度、节间生长显著高于其它3个处理。4种成分L25(56)的正交试验结果表明,琼脂0.1 g·L-1+蔗糖1 g·L-1+硼酸0.003 g·L-1+二水合氯化钙0.000 0 g·L-1+赤霉素0.000 6 g·L-1组合是‘优一’花粉萌发的最佳组合;‘优一’花粉在适宜萌发条件下,2~4 h是‘优一’花粉萌发的高峰期,蔗糖和硼酸是影响花粉萌发的最关键因素。     

云杉花粉的贮藏及萌发研究

研究了云杉花粉在离体培养条件下,蔗糖浓度、pH值、贮藏条件对其萌发和花粉管生长的影响,同时还优化了培养基的组分配比。结果表明:培养基中蔗糖浓度和pH值对云杉花粉的萌发影响显著,并有明显的交互效应。蔗糖低浓度和高浓度都不利于云杉花粉的萌发。不同的云杉种对培养基中蔗糖浓度要求不同,粗枝云杉和欧洲云杉花粉萌发的适宜培养基的蔗糖浓度和pH值分别为7.5%、5.5,10%、5.5。在暗培养条件下,欧洲云杉花粉6 h开始萌发,粗枝云杉8 h开始萌发,欧洲云杉较粗枝云杉提早2 h,同时欧洲云杉花粉萌发率总体高于粗枝云杉;欧洲云杉花粉管的生长历程为20 22 h,而粗枝云杉为16 h左右;欧洲云杉的花粉管长度比粗枝云杉长10μm以上。2种云杉不同个体基因型间的花粉萌发率和花粉管长度存在极显著差异。贮藏方法对花粉的生活力有很大影响,在云杉花粉保存过程中温度是主要条件,冷冻比冷藏好,不宜常温保存。     

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.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.