丽格海棠叶片的组织培养研究

取丽格海棠叶片作外植体,通过试验,分析不同激素配比对芽的诱导、增殖及生根的影响,筛选出丽格海棠叶片组织培养的适宜培养基及试管苗最佳移栽基质。结果表明：其最佳诱导培养基为MS＋6-BA1．5mg／L＋NAA0．8mg／L,不定芽诱导率达100％;最佳继代培养基是MS＋6-BA1．0mg／L＋NAA0．5mg／L,增殖倍数达6．5倍;最佳生根培养基是1／2MS＋NAA0．4mg／L,生根率达100％;试管苗最佳移栽基质为用1／2MS大量元素浇透的草炭,移栽成活率为85％。     

丽格海棠外植体筛选和培养的研究

以丽格海棠为试材,研究了不同外植体、不同生长素及大量元素含量对不定芽分化和试管苗生根的影响。结果表明,适宜丽格海棠组织培养的外植体为花梗,其次为叶片;适宜不定芽增值的培养基为MS＋BA1．0mg／L＋NAA0．1mg／L＋食糖30g／L＋琼脂8g／L,pH5．8;适宜试管苗生根的培养基为1／2MS＋IBA 0．1mg／L＋食糖30g／L＋琼脂8g／L,pH5．8,在培养后期,为获得壮苗可改用MS＋IBA 0．1mg／L＋NAA 0．1mg／L＋食糖30g／L＋琼脂8g／L。     

红叶石楠组织培养快速繁殖技术研究

红叶石楠是一种优良的彩色观叶园林植物，采用植物组织培养方法对其快速繁殖技术进行研究。结果显示：外植体诱导培养基采用MS＋6-BA0．5mg／L＋IBA0．1mg／L，不定芽的诱导率达76％；增殖培养基采用MS＋6-BA2.0mg/L＋KT0.5mg／L＋IBA0．2mg／L，丛生芽增殖率达6．32倍；生根培养基为1／2MS＋NAA0．5mg／L＋CCO0．5mg／L，生根率达100％。     

绒毛白蜡成熟胚和茎段培养繁殖体系的建立

以绒毛白蜡成熟胚和茎段为外植体，研究了培养基、激素组合对繁殖系数和生长的影响，适合绒毛白蜡离体繁殖的培养基为WPM培养基，胚萌发率为100％，4—5天萌发成幼苗；最适分化培养基为MS＋BA4．0．6．0mg／L＋NAA2．0mg／L，分化率为39．29％，平均增殖系数为3．59；生根培养基为1／2MS＋IBA1．5mg／L，生根率达65．0％。     

木瓜海棠组织培养技术的研究

以木瓜海棠当年生嫩枝上带有腋芽的茎段为外植体，运用对比试验和正交设计等方法，对木瓜海棠试管苗的快繁、生根、叶片和茎段愈伤组织的诱导进行研究。结果表明：快繁最适培养基为：MS＋6-BA1．0mg／L＋NAA0．1mg／L＋2，4-D0．2mg／L，增殖系数可达8．7；采用一步生根法最佳培养基为：1／2MS＋IBA1mg／L＋NAA0．2mg／L；在MS＋6-BA4．0mg／L＋2，4-D0.5mg/L的培养基上愈伤组织生长的较快，结构正常。     

西南桦优选株系组培快繁技术研究

对西南桦不同种源优选株系萌芽条离体快繁技术的初代培养、增殖培养、生根培养和移栽等方面进行研究。结果表明,初代培养最适培养基为改良MS＋6-BA3．0mg／L＋NAA0．25mg／L＋光照14h／d,芽体分化率最高达57．8％;最适增殖培养基为改良MS＋6-BA2．5mg／L＋NAA0．25mg／L＋糖35g／L;生根培养基为1／2改良MS＋IBA1．0mg／L＋NAA0．1mg／L＋IAA0．10rag／L;组培苗移栽基质为70％泥炭土＋30％红心土。     

大叶女贞组培快繁体系的建立

选用大叶女贞1年生木质化带芽茎段、腋芽、幼嫩新梢、萌蘖茎段和秋梢为外植体进行组织培养研究,结果表明：最适消毒处理是0．1％HgCl2 5min,最适外植体是萌蘖茎段和幼嫩新梢。萌蘖枝条适宜的起始培养基为MS＋6-BA 0．5mg／L＋NAA 0．1mg／L;幼嫩新梢适宜的起始培养基是MS＋6-BA 1．0mg／L＋NAA 0.05mg／L;最适增殖培养基是MS＋6-BA 4．0mg／L＋NAA 0．1mg／L,增殖系数为4．42。     

火鹤组织培养与快繁技术研究

以火鹤茎尖作为外植体进行组织培养，得出了愈伤组织的诱导发生、不定芽的分化诱导、生根的最佳培养基分别为：MS＋NAA0．05mg／L＋6-BA1．0mg／L，MS＋NAA0．20mg／L＋6-BA0．5mg／L，1／2MS＋NAA0．10mg／L；蛭石是火鹤组培苗移栽炼苗的最佳基质，成活率可达到100％。     

不同因素组织培养对山苍子茎段腋芽生长发育的影响

以山苍予带腋芽的茎段为外植体。研究了影响茎段诱导分化丛生芽、增殖与生根的主要影响因素。结果表明：山苍子通过茎段外植体直接分化丛芽进行离体培养的途径。最佳丛生芽诱导分化的培养基是1／2MS＋6-BA2.0mg／L＋NAA0.1mg／L，＋AC0.5g／L；最佳增殖培养基为WPM-6-BAl．0mg／L十IBA0．1mg／L＋Vclmg／L，以不定芽形式增殖，增殖系数为5．6，增殖周期为30d左右；生根培养基为改良1／2MS＋NAA0.3mg/L＋IBA0.2mg／L＋AC0.5g／L，生根率91％。     

华灰莉木的组织培养与快速繁殖

文章对华灰莉木组织培养快繁育苗技术进行研究。结果表明,以华灰莉木嫩茎为外植体,不定芽增殖系数高达2．095倍,持续增殖培养时,每个继代周期约有35％～40％的不定芽可分切转生根培养。适宜华灰莉木不定芽快速增殖的培养基为MS＋6-BA3．0mg／L＋NAA0．1mg／L,或MS＋6-BA3．5mg／L＋NAA0．2mg／L,蔗糖30g／L;而诱导生根的适宜培养基为1／2MS＋IBA1．0～2．0mg／L,蔗糖15g／L,生根率达94％。生根试管植株炼苗后移植存活率达90％。     

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.     

qPCR quantification of Ophiognomonia clavigignenti‐juglandacearum from infected butternut trees under different release treatments

The use of a molecular assay for quantifying conidia of Ophiognomonia clavigignenti‐juglandacearum, the fungal pathogen responsible of butternut canker, was investigated. Purified DNA from conidia collected on glass fibre filters of a passive rain collectors was quantified using a TaqMan real‐time quantitative polymerase chain reaction (qPCR) assay. The qPCR assay could specifically discriminate the target species from all other North American known species of Ophiognomonia, and it was sensitive enough to repeatedly detect one conidium. A linear relationship between numbers of conidia and qPCR C_t values was determined, and used to assess the sporulation of the pathogen under trees that were released to promote their vigour. In total, 977 samples of field‐captured conidia from 49 trees, at two locations, and from two successive growing seasons were analysed. No significant difference of sporulation was observed under control and release treatments. However, our results demonstrated that qPCR assay was reliable for detecting and quantifying O. clavigignenti‐juglandacearum from environmental samples, which will be useful to assess further control methods for this disease.     

The potential of alley cropping in improvement of cultivation systems in the high rainfall areas of Zambia I. Chitemene and Fundikila

Three trials investigating the potential of alley cropping to improve the traditional systems of cultivation, chitemene and fundikila, in the Northern Province of Zambia are described. Flemingia congesta, Tephrosia vogelii, and Sesbania sesban, were grown in association with finger millet, groundnut, cowpea, and maize in various traditional cropping sequences. The indigenous species Tephrosia vogelii and Sesbania sesban were not able to withstand repeated pruning and the long following dry season, and were replaced with Calliandra calothyrsus, and Cassia spectabilis.Over a four year period, there was no benefit by alley cropping with any of the tree species on crop yields, and yields in alley crop treatments even dropped significantly below the control treatments in the fourth year, casting doubt on the potential of alley cropping for sustainable production. There was also no consistent effect on soil chemical characteristics in any of the trials. It was suggested that this lack of beneficial response to alley cropping was due to low tree biomass production low quality of prunings, and an inappropriate cropping sequence. There was no evidence that alley cropping contributed to enhanced nutrient recycling, despite substantial localised pools of soil nutrients, particularly in the chitemene, with which recycling could potentially occur.     

Toxicity of biocide GCSC-BtA on arthropod pests under different temperature conditions

The present research dealt with the toxicity of GCSC-BtA (Germany–China Scientific Cooperation-Bacillus thuringiensis-Abamectin), a new type biocide developed by conjugating a toxin from Bacillus thuringiensis (B.t.) with Abamectin from Streptomyces avermitilis, on arthropod pests under different temperature conditions. The results showed that GCSC-BtA possessed higher toxicity than B.t. crystal, Abamectin or Cypermethrin, with pest mortalities of 97.9, 93.7, 96.4, 82.3 and 96.7% for Tetranychus cinnabarinus (Boisd.) (Acari, Tetranychidae), Frankliniella occidentalis Pergande (Thys., Thripidae), Aphis fabae Scopoli (Hom., Aphididae), Plutella xylostella (L.) (Lep., Plutellidae) and Cameraria ohridella Deschka et Dimić (Lep., Gracillariidae), respectively. Toxicities of GCSC-BtA to T. cinnabarinus and P. xylostella decreased significantly at the older developmental stage with an exception that egg stage had the highest tolerance, in which LC₅₀s of GCSC-BtA were 0.0001, 0.0019 and 0.0708 mg/ml for nymph, adult and egg of T. cinnabarinus, and that 0.0399, 0.2035 and 0.9033 mg/ml for the 2nd instar larvae, 4th instar larvae and egg of P. xylostella, respectively. Also, the biocide was more effective to the lower stage of A. fabae than the higher one with LC₅₀s of 0.0023, 0.0086 and 0.0171 mg/ml against 1st instar nymph, 3rd instar nymph and adult, respectively. In general, toxicity of the new type of biocide was positively related to temperature against all the tested pests, except against T. cinnabarinus, where it was almost similar at the three temperature conditions. GCSC-BtA displayed significantly lower toxicities at 15/20°C than 20/25°C or 25/30°C against F. occidentalis, A. fabae, P. xylostella and C. ohridella. However, no significant difference was found in the toxicities against F. occidentalis, A. fabae and C. ohridella above 20°C, whereas toxicity against P. xylostella increased as temperature raised. Therefore, to achieve higher efficacy in the field, application rate and time should be devised according to these factors.