Soil microorganisms alleviate the allelopathic effect of Eucalyptus grandis × E. urophylla leachates on Brassica chinensis

Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis x E. urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden (soil A) or a Eucalyptus plantation (soil B) and half of each soil was sterilized to remove microbes. These soils were then treated with E. grandis x E. urophylla leachates for 0-72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachate-treated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils. Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.

Comparative microsporogenesis and flower development in Eucalyptus urophylla×E.grandis

Microsporogenesis and flower development in Eucalyptus urophylla × E. grandis were examined using chromosome tableting to provide a method to predict the meiotic stages in this species. Although microsporogenesis was normal, cytokinesis during meiosis of pollen mother cells occurred simultaneously, with strong asynchronism observed in the two different lengths of stamens in a flower bud. In a single flower, the developmental period of microsporogenesis in anthers on the longer stamens was always ahead of those on the shorter stamens. Flower development was also asynchronous at different locations on a branch. Flower buds on the upper side of the branch were larger in diameter than those on the lower side. In addition, a correlation was observed between microsporogenesis development and flower bud diameter growth. The pachy- tene stage was first observed when the diameter of the flower buds increased to 3.0 mm, and the majority of the meiotic stages were observed when bud diameters ranged from 3.5 to 5.0 mm. This study showed that the developmental stages of microsporogenesis in Eucalyptus urophylla × E. grandis could be distinguished readily, which may be applicable to future breeding studies.

Monoterpene hydrocarbons,major components of the dried leaves essential oils of five species of the genus Eucalyptus from Cote d’Ivoire

The chemical composition of the essential oils obtained from the dried leaves of five species of the genus Eucalyptus (E. camaldulensis, E. de-glupta, E. grandis, E. torelliana, E. urophylla) growing in C?te d’Ivoire, was analyzed by means of GC and GC/MS. The density and the refractive index were measured. The major components of all these oils are: α-pinene, β-pinene, α-phellandrene, limonene, γ-terpinene, p-cymene and β-caryo-phyllene. The particularity of these oils is their monoterpene hydrocarbons major components.

Study on Machining Properties of Eucalyptus urophylla×E. grandis:I. Planing and Sanding Properties

The research method in this paper is based on the standard of American Society for Testing andMaterials (ASTM). Planing and sanding are selected to study the machining properties of E. urophylla × E.grandis plantation wood. Moreover, the reasons for machining defects are analyzed. The results show E.urophylla × E. grandis planted in south China is a good species with a great potential for solid woodutilization.

Influence of Planting Spacing on Mechanical Properties of Eucalyptus grandis × E. urophylla Planted in China

The objective of this study was to understand influence of planting spacing on mechanical properties of Eucalyptus grandis × E. urophylla planted as a potential species for solid wood products in China. Four trees at age of 13 were selected from each of 6 groups of planting spacing and a total of 24 sampling trees were selected from the Dongmen Forestry Center of Guangxi Province in China. Furthermore, a one-meter-long log from each tree was cut into small blocks for wood properties testing. MOE, MOR and compression strength parallel to wood grain were determined in accordance with Chinese standards. In addition, wood density and shrinkage properties were measured. Statistical analysis by SAS software indicated significant differences among the 6 groups of planting spacings on the air-dried density, radial shrinkage and bending MOR properties at the 0.05 level, and also on the compression strength at the 0.10 level. However, it was observed that there is no significant differences among shrinkages in tangential and volume, and MOE.

Growth Process of Eucalyptus urophylla × E.grandis Stand Based on Logistic Equation

Eucalyptus is the most valuable cultivated forest genus in the tropical and subtropical areas nowadays. It has been a challenge for foresters to model growth due to the genetic variations, management regimes, and multiple products generated from the plantations. In this paper, Logistic equation was used to study the stock growth process of E. urophylla × E. grandis plantation at age of 14 with 6 spacing treatments. And the biological interpretation of the parameters of Logistic equation was analyzed. The results show that it is flexible, precise and accurate to fit the growth process.

Study on Machining Properties of Eucalyptus urophylla× E.grandis:Ⅱ.Shaping,Boring,Mortising and Turning

The research method of this paper is based on the standards of American Society for Testing and Materials (ASTM). Four items that contain boring, mortising, shaping and turning are selected to study the machining properties of E. urophylla × E. grandis plantation wood. The reasons for machining defects are analyzed. The resultshows thatE. urophylla × E. grandis planted in South China isa good specieswith great potential for solid wood utilization.

Effect of Initial Moisture Content on Solar Drying Ratefor Eucalyptus grandis × E. urophylla

Wood drying is one of the most important process links in wood products processing.However, the existing drying methods mainly depend on heat to desiccate wood, which makes wooddrying consume roughly 40% - 70% of the total energy in the entire wood process. Using solar energyfor drying is greatly significant in two aspects of energy conservation and environment protection. Themoisture content (MC) of lumber affects not only the target value of wood drying, but also the heattransfer properties, moisture rate of expansion, etc., affecting dried lumber quality and drying rate.Eucalyptus grandis × E.urophylla lumbers were collected from Guangdong as test materials and dried inthe solar dryer with low temperature schedule and the effect of initial moisture content were primarystudied on drying rate. Experiments showed that solar drying was suitable for timber with high MC. Interms of drying rate and dried lumber quality, solar drying was as good as traditional steam drying withthe same schedule. And the solar dryer had distinct energy-saving effect.

尾细桉的组织培养和快速繁殖

以尾细桉M 1的单芽茎段为外殖体进行离体培养和快速繁殖研究.结果表明,再生芽诱导的较好培养基为EU+BA 0.5+NAA 0.2.增殖较适宜的培养基为EU+BA 1.0+NAA 0.2,EU+BA 0.5+IBA 0.2,EU+BA 0.5+NAA 0.1+IBA 0.1,每个芽可产生5个芽.壮苗较适培养基为1/2MS附加AC 0.5%～1.0%,有效苗品质高.生根较适培养基为1/2 MS附加NAA 0.2或IBA 0.2,生根率95%以上.炼苗移栽成活率达到96%以上.

尾细桉无性系在雷州半岛的适应性及稳定性评价

对5年生42个尾细桉无性系（含对照）在国营雷州林业局的年均材积生长量进行适应性及稳定性分析，结果表明：12个无性系具有显著或极显著正向增益，正向增益在10．25％～38．48％之间；适应性评价出适应品种15个，其中唐家林场5个，北坡林场4个，石岭林场6个；稳定性评价出高产稳定型无性系19个，高产不稳定型无性系5个，低产稳定型无性系7个及低产不稳定型无性系11个；3．01、LL244号无性系在好的立地上生长快，LH5和12246号在各类立地上均生长迅速，具较高生产力，生长稳定，评价结果对优良无性系选育及推广具有实际意义。

两种施肥措施对尾细桉的生长影响

采用同基肥条件下施用不同量追肥及同质量下NW和HY两种不同肥料的施肥措施,对处于该措施下的尾细桉生长状况进行研究。结果表明:不同追肥量下,追肥量为2 500 g的F1000-1-HY处理效果最佳,胸径和树高均优于其他处理。建立追肥量与17个月生和30个月生尾细桉的树高、胸径关系显示,树高均以线性拟合效果较好,拟合度分别达0.621 1和0.814 8;胸径均以二次函数拟合较好,拟合度分别达0.739 9和0.718 6。同质量的NW肥和HY肥处理下,HY肥优于NW肥,二者相对于对照组在17个月生和30个月生时,材积分别提高了140%、100%和157%、121%。

桉树离体快繁研究

以细尾桉为试材进行离体快繁研究。结果表明:通过二步消毒法,0.1%升汞能有效控制褐变,提高芽苗成活率;芽苗增殖较适宜的培养基为MS+0.5 mg.L-1BA+0.2 mg.L-1NAA;生根较适宜的培养基为1/2 MS+0.2 mg.L-1NAA,生根率达96%以上。

尾叶桉×细叶桉木材密度与生长的联合选择

[目的]评估Resistograph钻刺法间接测定尾叶桉×细叶桉木材密度的可靠性,检测杂交亲本对子代表型的效应以及生长与木材密度的相关,评选速生、优质的尾细桉杂种。[方法]基于10株尾叶桉与10株细叶桉不完全析因交配产生的56个杂交组合的7.5年生试验林,利用79株分析容积法与Resistograph钻刺法测定的木材密度的相关,通过方差分析检测亲本对杂种生长和木材密度的效应,结合多重比较和独立淘汰法进行材积和木材密度的联合选择。[结果]容积法与Resistograph钻刺法测定的木材密度的表型相关系数为0.52(P<0.001),遗传相关系数为0.55(P<0.05);树高、胸径及材积的母本间和父本间均呈极显著差异(P<0.001或0.01),但母本×父本互作的效应不显著;对钻刺木材密度,父本间呈极显著差异(P<0.001),母本×父本互作显著(P<0.05),但母本间差异不显著;树高、胸径和材积间的表型相关和遗传相关均极显著(P<0.001),其与钻刺木材密度的表型相关极显著(P<0.001),但遗传相关不显著;评选出速生、木材密度较高的杂交组合14个、单株17株。[结论]Resistograph钻刺法是一种间接测定尾细桉木材密度的简便、经济和可靠的方法;母本和父本选择以及母本与父本的组配对培育速生、材质优良的尾细桉杂种均较重要;尾细桉生长与木材密度的遗传相关不显著,需要对这两类性状分别进行选择;评选的尾细桉杂交组合和单株为培育速生、优质的桉树良种提供了有用的材料。

尾巨桉愈伤组织蛋白质含量和氧化酶活性比较

以尾巨桉(Eucalyptus urophylla×E.grandis)无性系DH32-29无菌苗的茎段为外植体,优化的激素组合的愈伤组织诱导率高,随后培养中愈伤组织分化出绿色、黄绿色、白色和褐色4种类型,绿色和部分黄绿色的为胚性愈伤组织,后两种为非胚性愈伤组织。分别测定不同类型愈伤组织的蛋白质含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,结果表明,愈伤组织蛋白质含量从高到低为绿色、黄绿色、白色、褐色;胚性愈伤组织的SOD、POD和CAT活性显著高于非胚性愈伤组织,并且绿色愈伤组织3种酶活性均高于其他愈伤组织。

3种肥料处理对尾细桉生长的影响研究

在总养分含量相同条件下研究了有机—无机复混肥A(包括基肥、追肥)、有机—无机复混肥B(包括基肥、追肥)、无机肥C 3种肥料处理对尾细桉生长的影响。结果表明施用有机—无机复混肥A的处理在苗木生长17个月的时候长势最好,与其他3种处理差异达到极显著水平。在生长30个月时,施用有机—无机复混肥A处理与B处理生长均较好,两者差异不显著,但是均与C处理差异显著。说明肥料和施肥方式会对尾细桉的生长有影响;添加有机质会提高桉树尾细桉的产量。

尾巨桉DH_(32-26)组培快繁技术

[目的]探索尾巨桉DH_(32-26)组培快繁技术,为其规模化生产提供参考。[方法]采用组织培养手段,以尾巨桉DH_(32-26)半木质化萌发茎段为材料,对外植体诱导及无菌组织培养体系进行研究。[结果]最佳外植体诱导培养基为改良MS+6-BA 1.0 mg/L+NAA 0.5mg/L,发芽率为92.3%;最佳增殖培养基为改良MS+6-BA 0.4 mg/L+NAA 0.2 mg/L,增殖个数为3.7;最佳生根培养基为改良1/2MS+IBA 0.2 mg/L+ABT 0.3 mg/L,生根率可达98.3%。[结论]该研究获得了尾巨桉初代诱导、增殖和生根适宜培养基和培养条件,初步达到工厂化生产要求。

冷处理对尾巨桉几种生理指标和POD基因转录的影响

6℃冷处理尾巨桉(Eucalyptus urophylla×E.grandis)半年龄树苗24 h后,检测叶片电导率、叶绿素含量、丙二醛含量、可溶性蛋白质含量、SOD活性、POD活性等生理指标的变化,进行POD同工酶电泳,并用实时定量PCR(Real-time quantitative PCR,q PCR)检测了4个POD基因的转录变化。结果表明,与常温相比,冷处理后尾巨桉的叶绿素含量、可溶性蛋白质含量和SOD活性无明显变化;但相对电导率、丙二醛含量和POD活性都有升高,且与常温下有显著差异。POD同工酶电泳结果显示,冷处理后,L1、L2、L8、L9和L10共5个酶带表达增强;L3、L4、L5、L6、L7共5个酶带的表达明显受到抑制。实时定量PCR检测POD1、POD2、POD3、POD4基因的转录变化发现,低温处理后4个基因的转录明显被抑制,其转录水平分别是常温下的0.21、0.41、0.40和0.21倍。上述结果表明,低温胁迫对尾巨桉的相对电导率、丙二醛含量、POD活性、POD同工酶表达变化和POD基因的转录水平等指标有显著影响,低温下这几个指标的变化幅度可作为筛选耐寒性较强尾巨桉株系的参考。

Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.

Use of Near Infrared Spectroscopy to Measure Mechanical Properties of Solid Wood

The visible and near infrared(NIR)(350-2500 nm)spectra and the MOE of 438 small clear wood samples from Chinese fir,eucalyptus and poplar 72 were measured.Using partial least-square(PLS)modeling,the NIR spectra could be used to predict MOE and MOR of the clear-wood samples from Chinese fir and eucalyptus solid wood.NIR spectra could only be used to predict MOE but not MOR of poplar clear-wood samples.With the exception of MOR of poplar clear-wood samples,the correlations between NIR and the mechanical properties are very strong,and the calibration and test correlation coefficients are both above 0.80.

不同坡向对尾巨桉人工林林下草本植物多样性的影响

为了解不同坡向对尾巨桉(Eucalyptus urophylla×E.grandis)人工林林下草本植物多样性(Margalef指数dMa、Simpson指数D、Shannon-wiener指数H、Pielou指数J)的影响,以云南省临沧市双江县忙安林场8年生人工林为研究对象,设置不同坡向(阳坡、半阳坡、阴坡、半阴坡)的12个样地进行调查。研究结果显示:1)尾巨桉人工林共调查统计到林下草本植物30种,隶属16科28属,草本层植物物种数在阴坡、半阴坡相同且均高于阳坡、半阳坡。2)不同坡向尾巨桉人工林林下草本物种主要以禾本科的芭茅、菊科的紫茎泽兰为优势物种,占据主导地位。3)不同坡向尾巨桉人工林林下草本层植物在半阴坡的dMa、D、H、J值最大,阳坡最小。综合不同坡向尾巨桉人工林林下植物多样性指数分析比较,阴坡更有利于林下草本植物的生存。