Genetic Control of Air-Dried Wood Density, Mechanical Properties and Its Implication for Veneer Timber Breeding of New Triploid Clones in Populus tomentosa Carr

The wood samples of 9 triploid clones of Populus tomentosa Carr. taken from a 9 year old clonal test site were analyzed in order to investigate the genetic variation of wood properties, including air dried wood density and some mechanical properties. The results showed that significant or extremely significant difference in air dried wood density and the mechanical properties existed among the clones, this means these wood properties were under moderate or strong genetic controls and could be improved by genetic manipulations. The radial and vertical variation patterns of air dried wood density were also studied and the results were found to coordinate with other previous research results. The vertical variation patterns of most mechanical properties within the individual tree also conformed to the general wood theories except the modulus of elasticity and cross section hardness. Among the mechanical properties, modulus of elasticity (MOE) and tangent section hardness were under strong genetic control, with the clonal repeatabilities being 0 90 and 0 80, respectively. However, the clonal repeatabilities of other mechanical properties under study were a little lower than above two indexes. Genetic correlation analysis indicated that super clonal selection and breeding for veneer timber could be realized through indirect selection of wood density and form indexes.

Lignin Characterization of Triploid Clones of Populus tomentosa Carr.

In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.

THE FIBER MORPHOLOGY VARIATION OF TRIPLOID CLONE OF POPULUS TOMENTOSA CARR.AND ITS SUPPOSED HARVESTING AGE FOR THE PAPER INDUSTRY

The fiber morphology variation of triploid clone of Populus tomentosa Carr. and the supposed harvesting age for the paper industry were investigated in this paper. The results shows that in the first few years, 2-4 years for example, the fiber length at breast high grows faster than it does in the later years. But the standard deviation of distribution in fiber length at breast high in mature wood is larger than in the young tree. The technologically harvestable age of triploid clone of Populus tomentosa Carr., BL304 could be 4-7 year old to meet the requirement for paper industry. The distribution of fiber length become concentrated within an annual ring as the tree grows. The test results also show that the cloned poplar has a small Runkel ratio value (less than 0.4, generally about 0.3), and this ratio increases slightly with the tree grows.

Selection of Media for Hardwood Cuttings Container Seedling-raising of Triploid Clones of Populus tomentosa

[Objective] The experiment was aimed to select effective and economical media for container seedling of triploid clones of Populus tomentosa that was carried out. [Method] The sandy loam, peat, perlite, vermiculite, riversand, sludge were taken as media of hardwood cutting and survival rate, seedling height were taken as indexes to select media for container seedling of triploid clones of Populus tomentosa. [Result] Different mixedmedia had great influence on survival rates of container seedlings. Taking peat and vermiculite with the proportion of 5∶2 (M10) or peat ,vermiculite with the proportion of 7∶2 (M11) or sandy loam (M1) as media would generate higher cutting survival rate that was higher than 90.0%. There were significant differece in height increments of container seedlings. Taking sandy loam, peat and vermiculite with the proportion of 6∶2∶2(M5)or sandy loam (M1), seedling height of 60-days the seedling was over 37.0 cm. [Conclusion] According to cost analysis of nursery medium, the optimum medium for hardwood cuttings container seedling-raising of triploid clones of Populus tomentosa was sandy loam.

Cloning and Expression Analysis of PtFATB Gene Encoding the Acyl-acyl Carrier Protein Thioesterase in Populus tomentosa Carr

Acyl-ACP thioesterases （FATs） terminates the fatty acid synthesis and allow the transport of fatty acids out of the plastids, which are the important determinants of cellular metabolism. FATB is a member of FAT enzymes that has been described previously in most of the plants. In silico cloning is a new method that utilizes the bioinformatics on the complete genome and available EST database. In this study, a full-length cDNA clone of PtFATB gene was isolated from Populus tomentosa using this approach. It is 1,450 bp in length and the open reading frame encodes a peptide of 421 amino acids. The predicted amino acid sequence shows significant homology with those from other plant species, which contain typical domains owned by FATB proteins. The transcripts of PtFATB were abundant in leaves, and less in roots detected by using semiquantitative RT-PCR. When the shoots were subjected to the stress treatments （cold, dry, NaC1） and ABA （Abscisic acid）, the expression of PtFATB was only slightly reduced under the treatment of low temperature. This suggests that the expression of PtFATB is in a constitutive fashion. This study provides the basis not only for the identification and characterization of this gene but also for the improvement of cold tolerance by controlling the expression of the PtFATB gene in trees in near future.

Segregation of AFLP Markers in A ( Populus tomentosa× P. bolleana) ×P. tomentosa Carr. BC_1 Family

To investigate the levels of polymorphisms and Mendelian segregation ratio in clone “TB01” (P. tomentosa×P. bolleana) ×clone “LM50” (P. tomentosa) BC 1 population at the entire genome level, amplified fragment length polymorphisms (AFLPs) analysis was conducted for both parents and 120 progenies. Forty one pairs of selective primers were used to detect 2?707 bands, of which 712 (26.4%) were polymorphic. Chi\|square tests were performed to examine if the observed genotypic frequencies of AFLP loci deviated from expected 1∶1 Mendelian segregation ratio ( P <0.01) in BC 1 population. Among the 712 loci 571 (80.2%) fit to Mendelian 1∶1 segregation ratio, corresponding to DNA polymorphisms heterozygous in one parent and a null in the other. The result shows that the AFLP markers are very suitable for fingerprinting and genetic mapping in the Chinese white poplar (Populus tomentosa Carr.).

Variation of Leaf Characteristics in Populus tomentosa Carr

An investigation was conducted to determine the extent of variations among nine provenances of Populus tomentosa Carr. in terms of leaf characteristics. A total of 263 accessions were studied under field conditions in the National Gene Bank of P. tomentosa in 2003. All of the accessions were characterized by 17 indices from 1 to 2-dimension constructions. Variance analysis of all characteristics showed that there were significant differences among the nine provenances and among individuals within each provenance. This study reveals that the evaluated germplasm appears to have a wide genetic base and high potential for further genetic improvements and it also indicates that abundant gene resources of P. tomentosa have been collected and preserved in the National Gene Bank.

Incidence and molecular markers of 2n pollen in Populus tomentosa Carr

Microscopic examination and AFLP molecular markers were employed to determine the incidence and related markers of 2n pollen (unreduced pollen) in Populus tomentosa Carr. The parallel and tripolar spindle at metaphase Ⅱ and the absence of cytokinesis at telophase Ⅱ led to the formation of 2n pollen. A group of 298 clones came from their indigenous areas was investigated for the production of 2n pollen based on the pollen size differences, within a clone and between n and 2n pollen. Pollen grains of 224 clones were collected, six of them only produced normal pollen, and the rest produced 2n pollen at different frequencies (0.6% -21.9%). Clones producing six normal and 22 2n pollen were selected for AFLP analysis. Following an initial screening with 55 primer combinations, the E50-M38 (CAT/ACT) primer was identified, which generated a PCR fragment (246 bp) from the normal clones, but not from the 2n pollen producers. In addition, the E31-M50 (AAA/CAT) amplified DNA fragment (204 bp) that was present in 2n pollen producers, and absent in normal clones. Two polymorphic bands were found and they were distinguished between normal and 2n pollen clones. They are very useful as AFLP markers for molecular-assisted selection in triploid breeding of 2n gametes in P.tomentosa.

Interrelationships between leaf heat conductivity and tissue structures of different varieties of Populus tomentosa Carr

Plant heat conductivity largely depends on tissue structure. Different structures lead to different heat conductivity. As well, water transfer also plays a very important role in heat transfer in plants. We have studied leaf heat conductivity and tissue structure of 3- and 30-year-old Populus tomentosa Carr. trees using infrared thermal imaging, steady state heat conductivity surveys and paraffin section and investigated the relationship between leaf heat conductivity, tissue structure and water content of leaves. The results show that the temperature on leaf surfaces among the various varieties of trees was almost the same. Leaf heat conductivity, temperature and water content of leaves are positively correlated. The thicker the leaf tissue structures, the larger the heat resistance. That is, the tighter the cells and the smaller the interspaces, the smaller the heat conductivity, which is not conducive for heat transfer.

Model of leaf energy distribution and its experimental validation of Populus tomentosa Carr

Leaf temperature of a plant is the result of heat transfer between the plant and its environment. There are many factors that can affect leaf temperature, such as the solar radiation energy, environmental temperature, wind velocity, evaporation on the leaf surface, photosynthesis, respiration and so on, which have different effects on the temperature of leaves. In first instance, we analyzed the heat transfer on leaves of Populus tomentosa Carr. theoretically and constructed a model of energy distribution. We then validated the model by analyzing seven different kinds of one-year-old P. tomentosa leaves experimentally. The result shows that solar radiation is the main energy input and the dominant ways of thermal diffusion are heat transfer between the upper and lower leaf surfaces and evaporation from the leaf surface.

Effects of Fertilization Treatments on Plantation Growth of Triploid Clones in Populus tomentosa

With four clones of triploid Populus tomentosa as materials, the effects of fertilization treatment on growth and physiological characters in terms of leaf nitrogen content, phosphorous content, potassium content, net photosynthetic rate, transpiration rate, water utilization efficiency and chlorophyll content have been studied. Compared with the general fertilizer as a control, the long-effect fertilizer, especially for Populus, produce more favorable results, for P. tomentosa on sandy land.

Duplication of Locus Coding of Malate Dehydrogenase in Populus tomentosa Carr

Horizontal starch-gel electrophoresis was used to study crude enzyme extraction from young leaves of 234 clones of Populus tomentosa Cart. selected from nine provenances in North China. Ten enzyme systems were resolved. One hundred and fifty-six clones showing unusual allozyme band patterns at locus Mdh-Ⅰ were found. Three allozyme bands at locus Mdh-Ⅰ were 9：6：1 in concentration. Further studies on the electrophoretic patterns of ground mixed pollen extraction of 30 male clones selected at random from the 156 clones were conducted and it was found that allozyme bands at locus Mdh-Ⅰ were composed of two dark-stained bands and a weak band. Only one group of the malate dehydrogenase （MDH） zymogram composed of two bands was obtained from the electrophoretic segregation of pollen leachate of the same clones. A comparison of the electrophoretic patterns one another suggested that the locus Mdh-Ⅰ coding malate dehydrogenase in diploid species of P. tomentosa was duplicated. The duplicate gene locus possessed three same alleles and was located in mitochondria. The locus duplication of alleles coding malate dehydrogenase in P.tomentosa was discovered and reported for the first time.

Establishment of High Frequency Regeneration System of Populus tomentosa

The establishment of high frequency regeneration system is a foundation for Agrobacterium mediated genetic transformation. In this work, several important factors influencing the efficiency of regeneration of plants, such as concentration of plant growth regulators, leaf explant orientation, leaf growth sequence and leaf segment, were studied. The results indicated that the differentiation rate of adventitious shoots was 90% on basal MS medium only supplemented with 1 5?mg·L -1 BA (6 benzyladenine) and reached the highest level(95%) when 1 0?mg·L -1 BA and 0 3?mg·L -1 NAA (naphthaleneacetic acid) were added to MS medium. 90% of differentiation rate of adventitious roots were obtained when 0 3?mg·L -1 NAA was only added to MS medium. It was also found that more adventitious shoots were regenerated from the lower segment of leaf (with petiole) than the other segments, the number of adventitious shoots decreased from top to base of leaf growth sequence and the percentage of adventitious shoot induction with adaxial side downward was higher than that with adaxial side upward.

Improvement in salt tolerance of Populus tomentosa from transformation by a mtl-D gene

Transgenic lines were achieved by transforming the E. coli 1-phosphate mannitol dehydrogenase gene （mtl-D） into the Populus tomentosa Cart. genome. An Agrobacterium tumefaciens strain （AGL1）, constructed by cloning mtl-D into the disarmed plasmid pBin438, was used to infect leaves of the clone YW2. The infected leaf discs were cultured on a medium containing 30 mg.L 1 kanamycin and 500 mg.L 1 cefotaxime. Transgenic plantlets regenerated from the infected leaves, rooted on the medium con- taining 30 mg.L 1 kanamycin. PCR and a Southern blotting test verified that the exogenous mtl-D gene had integrated into the trans- formation plants of the P. tomentosa genome. The mannitol content in control plant was 69 gg.gl FW, and the mannitol contents of the transgenic lines T1 to T5 ranged between 103.7 and 289.5 μg·g^-1 FW. Of the shoots of the control plants 20% survived; on the medium containing 0.6% NaCl, 60% and 70% of two transgenic shoots survived on a medium containing 0.8% NaCI.

Comparison and early selection of new clones in Populus tomentosa

In our study, two experimental plantations, respectively, with 24 and 32 new clones of P tomentosa, were established in Weixian County, Hebei Province and Wuzhi County, Henan Province using a completely randomized block design. A comparative study was conducted on the continuous 5-year-old height and diameter at breast height （DBH） of new clones in the two plantations. As well, based on genetic correlation over the years of testing of these clones, a preliminary study of early selection was carried out. Results indicate that the growth traits of the new clones in Weixian were better than those in Wuzhi. The traits show weak correlation between the two plantations. In some stands, the height, DBH and seedling volume of 5-year-old clones presented statistically significant differences among clones. In both plantations, the new clones showed over 0.6 repeatability of height, DBH and volume, as well as larger coefficients of variation （CV）. The fact that these clones achieved the largest repeatability and CV in the second year suggests that these traits are highly controlled by heredity. Thus, based on the growth traits of the second year, the new clones B305, B307, B303, H75, BT18, BT17 and 21J-1 were considered suitable in Weixian. In Wuzhi, the new clones had variable repeatability and CVs in various years and their correlation of growth traits among different years was not high. We conclude that early selection of new clones was not feasible in Wuzhi.

RESEARCH ON FIBER MORPHOLOGY AND PULPING PROPERTIES OF THE TRIPLOID OF PLPULUS TOMENTOSA FROM PLANTATION AT DIFFERENT AGES

The fiber morphology and pulping properties of triploid of populus tomentosa from plantation at different ages were investigated in the paper,also the main chemical compositions were determined. The results showed that the difference of chemical compositions is not significant, and the extractive contents become bigger in some sort with age, the difference of length weighted mean length of fiber also is not significant, and coarseness of fiber has trend of augment by degree, while the fines content increases obviously with age. That difference of pulping properties between chemical pulping (KP process and Soda-AQ process) and chemimechanical pulping (SCMP process and APMP process) is not significant, which is consistent with the analysis of chemical composition and fiber morphology. Considering comprehensively, the tree age of 5 years is better for paper making industry, also the mixed pulping with different ages of the triploid of populus tomentosa is feasible with steady pulp quality.

Establishment of in Vitro Regeneration System of Triploid Chinese White Poplar

初步建立了三倍体毛白杨 (PopulustomentosaCarr.)组织培养再生系统。组织培养时 ,外植体最好选用在弱光下从休眠芽上萌发的幼芽或嫩茎 ,经HgCl2 溶液表面消毒后 ,接种到大量元素减半、含 0 .2 5mg/L吲哚乙酸和 1.0 0mg/L玉米素的MS培养基上。试管苗的生根可采用含 0 .2 5mg/L吲哚丁酸和 10mg/L维生素B1的MS培养基。试管苗茎段的分化依无性系和外源激素条件的不同而异。无性系B19的茎段较易分化 ,而无性系B30 4和B331分化较难。最适的分化培养基为大量元素减半、含 0 .0 5～ 0 .10mg/L吲哚乙酸和 1.0

成年雄性毛白杨组培幼化技术研究

【目的】毛白杨以无性繁殖为主,而无性繁殖材料往往存在老化现象,严重影响苗木质量,研究繁殖材料的幼化技术对于改善苗木质量,促进无性林业发展有重要意义。【方法】以北京大兴区站上村的200年生雄性毛白杨为对象,取其根萌条为繁殖材料,探索2种灭菌试剂处理条件下,不同灭菌时间对外植体成活与生长的影响,同时在MS培养基中设置不同激素组合研究其增殖的最佳效果,筛选出适合其生长的最佳增殖培养基,通过继代培养研究此200年生成年雄性毛白杨的组培幼化技术。【结果】结果表明,0.1%氯化汞溶液的灭菌效果比10%次氯酸钠溶液效果好,最佳灭菌处理为0.1%氯化汞7 min,成活率为57%;最佳增殖培养基为MS+0.7 mg/L 6-BA+0.01 mg/L NAA,最高丛生芽分化系数为2.23,茎高生长量≥1 cm苗的数量比例为53.33%,显著高于其他处理;随着继代次数的增加,生长周期由63 d(1代)降至44 d(4代),继代培养增殖系数由0.93(1代)提升至4.85(4代),茎高生长量≥3 cm苗的数量比也从2.23%(1代)显著增至62.34%(4代)。【结论】此200年生毛白杨繁殖材料存在一定程度的老化现象,母株的年龄可能影响其根萌条的幼化程度,但随着继代次数的增加,生长势有了显著的提高,说明多次继代培养有较明显的幼化作用,且随着继代次数的增加,幼化效果也越好。

不同修枝处理对10年生三倍体毛白杨生长和光合特性的影响

为探讨中高林龄杨树(Populus)光合生理特性对不同修枝强度的响应规律,以10年生三倍体毛白杨(triploid Populus tomentosa)无性系B301与S86为研究对象,采用轻度修枝(修去树冠下部1/3枝条)和重度修枝(修去树冠下部1/2枝条),以及未修枝杨树为对照,研究不同强度修枝对10年生毛白杨生长和生理特性的影响。结果表明:对于10年生中高龄杨树,修枝对树高、胸径、材积增长率无显著影响,但重度修枝能提高剩余叶片的净光合速率(P_(n))、蒸腾速率(T_(r))、气孔导度(G_(s)),增强单叶水平上物质合成的能力,而修枝对瞬时水分利用效率(WUE)影响不显著。从生长和光合角度综合分析,修去树冠下部1/2枝条能够改善10年生毛白杨生理状况,但对林木生长无明显促进作用。

毛白杨凋落叶对节节麦种子萌发和表型可塑性的影响

以节节麦(Aegilops tauschii Coss.)种子和幼苗为研究对象,分别用毛白杨(Populus tomentosa Carr.)凋落叶浸提液和毛白杨凋落叶进行处理,探讨毛白杨凋落叶化感防除节节麦的可行性,并分析节节麦在化感逆境中的入侵机制。结果表明:毛白杨凋落叶化感物质对节节麦种子和幼苗均能产生明显的低促高抑化感作用,5 mg·mL^(-1)凋落叶浸提液对种子萌发有促进效应,大于等于40 mg·mL^(-1)时转为抑制效应,使发芽率、发芽势、发芽指数显著(P<0.05)降低,60 mg·mL^(-1)时抑制作用最强;毛白杨凋落叶低添加量(30 g)时,显著促进节节麦各部分构件生物量积累,显著增加总叶面积;施用120 g凋落叶可强烈抑制其生长,使根、茎、叶生物量,以及总叶面积、平均叶面积、叶生物量比、叶根比、相对生长速率显著(P<0.05)降低,证明毛白杨凋落叶对节节麦具备一定的化感作用,具备抑草潜力,高浓度毛白杨凋落叶化感物质显著抑制其种子萌发和植株生长。节节麦作为入侵植物,在适应环境的过程中,根、茎、叶均表现出较强的表型可塑性,尤其是叶片相关指标,总叶面积、叶重、叶生物量比的表型可塑性指数分别为0.81、0.78、0.34。