Genome Fingerprinting Analysis in Populus deltoides

The appraisal of cultivar authenticity is a problem that needs to be settled in agricultural and forestry activities. AFLP is a novel, reliable and effective technique in DNA fingerprint. 42 clones of Populus deltoides Mash. were fingerprinted with the technique. AFLP technique can be widely used in the practical cultivar identification.     

美洲黑杨材性相关候选基因PdCYTOB的功能鉴定

利用RT-PCR技术研究了美洲黑杨（Populus deltoides）材性相关候选基因细胞分裂素结合蛋白（cytokininbin ding protein）基因PdCYTOB的表达谱,结果显示,在未成熟木质部、未成熟韧皮部和韧皮部中PdCYTOB基因具有较高水平的表达量。对导入反义PdCYTOB的山新杨（Populus davidiana×P.bolleana）植株进行Southern杂交和RT-PCR检测,证实反义PdCYTOB基因已整合到杨树基因组中并表达。对大田转基因株系及对照植株进行表型观察、组织切片和微纤丝角的测定,结果表明,转反义PdCYTOB基因植株的高度明显增加,木质部、韧皮部变宽,微纤丝角明显变小,初步表明转基因杨树在造纸性能上有所改良。这些研究结果对于阐明PdCYTOB在美洲黑杨木材形成中的分子作用机制具有重要的理论意义。     

非结构性碳水化合物与氮分配对美洲黑杨和青杨耐盐能力的影响

土壤盐渍化是阻碍林业发展的重要原因, 杨树(Populus spp.)是中国主要的人工林树种, 探究盐胁迫下植物的碳氮代谢特征与抗盐胁迫能力, 将有助于杨树人工林的可持续发展。该研究利用美洲黑杨(P. deltoides)和青杨(P. cathayana)两个物种, 采用去叶与不去叶处理, 在盐胁迫下研究两种杨树的抗逆性差异。研究发现, 盐胁迫下美洲黑杨的总生物量和光合能力均显著高于青杨。盐胁迫与去叶处理导致美洲黑杨叶绿素浓度和光系统II最大光量子效率显著高于青杨, 表明去叶对美洲黑杨影响较小, 但是加重了盐对青杨的毒害作用。美洲黑杨茎叶Na⁺浓度显著低于青杨, 表明美洲黑杨能够有效地限制Na⁺向地上部分运输。在盐胁迫条件下, 美洲黑杨茎和根比青杨能够维持更高浓度的淀粉、可溶性糖以及蔗糖, 前者较高的腺苷二磷酸葡萄糖焦磷酸化酶活性促进了光合产物向淀粉转换, 保证植物有充足的非结构性碳水化合物来参与渗透调节和维持其他生命活动, 而去叶使得青杨非结构性碳水化合物严重不足, 受盐胁迫影响更严重。盐胁迫下, 青杨分布在脂溶性蛋白(膜系统相关蛋白质)的氮浓度显著下降, 而NH₄⁺、谷氨酸脱氢酶活性与脯氨酸浓度显著升高。研究结果证明, 非结构性碳水化合物的积累、转化和分配是植物抗逆性的重要特征。     

Effects of environmental conditions on isoprene emission from live oak

Live-oak plants (Quercus virginiana Mill.) were subjected to various levels of CO₂, water stress or photosynthetic photon flux density to test the hypothesis that isoprene biosynthesis occurred only under conditions of restricted CO₂ availability. Isoprene emission increases as the ambient CO₂ concentration decreased, independent of the amount of time that plants had photosynthesized at ambient CO₂ levels. When plants were water-stressed over a 4-d period photosynthesis and leaf conductance decreased 98 and 94%, respectively, while isoprene emissions remained constant. Significant isoprene emissions occurred when plants were saturated with CO₂, i.e., below the light compensation level for net photosynthesis (100 mol m^-2 s^-1). Isoprene emission rates increased with photosynthetic photon flux density and at 25 and 50 mol m^-2 s^-1 were 7 and 18 times greater than emissions in the dark. These data indicate that isoprene is a normal plant metabolite and not — as has been suggested — formed exclusively in response to restricted CO₂ or various stresses.Abbreviation PPFD photosynthetic photon flux density     

美洲黑杨不同无性系对分月扇舟蛾幼虫的抗性

以分月扇舟蛾Clostera anastomosis(L.)为材料,以I-72杨为对照,研究南京林业大学新近引进的18个美洲黑杨(Populus deltoides L.)无性系在实验室条件下的抗虫性,筛选出11个具有较强抗性的无性系,并分析不同无性系的抗性与其叶片中主要营养物质和次生代谢物质含量的关系,初步解释其抗性机理。其研究结果为今后进行林间试验,选育出在生产上具有推广价值的美洲黑杨优良抗虫品系提供科学依据。     

Arsenic tolerance and phytoremediation potential of Conocarpus erectus L. and Populus deltoides L.

The present study was conducted to explore arsenic (As) tolerance and phytostabilization potential of the two tree species, buttonwood (Conocarpus erectus) and eastern cottonwood (Populus deltoides). Both plant species were grown in pots and were exposed to various soil As levels (control, 5, 10, 15, and 20 mg kg^?1). The plants were harvested after 9 months for the evaluation of growth parameters as well as root and shoot As concentrations. With increasing soil As levels, plant height stress tolerance index (PHSTI) was significantly decreased in both tree species, whereas root length stress tolerance index (RLSTI) and dry matter stress tolerance index (DMSTI) were not affected. Root and shoot As concentrations significantly increased in both tree species with increasing soil As levels. Translocation factor and bioconcentration factor were less than 1.0 for both plant species. This study revealed that both tree species are non-hyperaccumulators of As, but they could be used for phytostabilization of As-contaminated soils.     

Genetic transformation of Populus deltoides and P.x euramericana clones using Agrobacterium tumefaciens

The susceptibility of different Populus euramericana (Neva, PE68-022 x P. nigra, 71-060 x P. nigra) and P. deltoides (PE68-022 x P. deltoides) clones to wild-type Agrobacterium tumefaciens strains (A281 and 82.139) was evaluated in an inoculation experiment, and differences in the frequency of tumor formation (0-48) were found. Co-cultivation experiments demonstrated high transformation ability of oncogenic binary A. tumefaciens strains as compared to disarmed strains. Using oncogenic binary strains, transgenic calluses were obtained from all tested clones. The presence of acetosyringone did not influence the transformation frequency of the disarmed strains. Co-inoculation experiments were performed using leaf discs and a bacterial suspension containing both wild-type and disarmed strains. No positive effects on transformation efficiency were noticed in these conditions either. The transformation of tumors and kanamycin resistant calluses was confirmed by DNA analysis.     

Environmental and developmental controls over the seasonal pattern of isoprene emission from aspen leaves

Isoprene emission from plants represents one of the principal biospheric controls over the oxidative capacity of the continental troposphere. In the study reported here, the seasonal pattern of isoprene emission, and its underlying determinants, were studied for aspen trees growing in the Rocky Mountains of Colorado. The springtime onset of isoprene emission was delayed for up to 4 weeks following leaf emergence, despite the presence of positive net photosynthesis rates. Maximum isoprene emission rates were reached approximately 6 weeks following leaf emergence. During this initial developmental phase, isoprene emission rates were negatively correlated with leaf nitrogen concentrations. During the autumnal decline in isoprene emission, rates were positively correlated with leaf nitrogen concentration. Given past studies that demonstrate a correlation between leaf nitrogen concentration and isoprene emission rate, we conclude that factors other than the amount of leaf nitrogen determine the early-season initiation of isoprene emission. The late-season decline in isoprene emission rate is interpreted as due to the autumnal breakdown of metabolic machinery and loss of leaf nitrogen. In potted aspen trees, leaves that emerged in February and developed under cool, springtime temperatures did not emit isoprene until 23 days after leaf emergence. Leaves that emrged in July and developed in hot, midsummer temperatures emitted isoprene within 6 days. Leaves that had emerged during the cool spring, and had grown for several weeks without emitting isoprene, could be induced to emit isoprene within 2 h of exposure to 32°C. Continued exposure to warm temperatures resulted in a progressive increase in the isoprene emission rate. Thus, temperature appears to be an important determinant of the early season induction of isoprene emission. The seasonal pattern of isoprene emission was examined in trees growing along an elevational gradient in the Colorado Front Range (1829–2896 m). Trees at different elevations exhibited staggered patterns of bud-break and initiation of photosynthesis and isoprene emission in concert with the staggered onset of warm, springtime temperatures. The springtime induction of isoprene emission could be predicted at each of the three sites as the time after bud break required for cumulative temperatures above 0°C to reach approximately 400 degree days. Seasonal temperature acclimation of isoprene emission rate and photosynthesis rate was not observed. The temperature dependence of isoprene emission rate between 20 and 35°C could be accurately predicted during spring and summer using a single algorithm that describes the Arrhenius relationship of enzyme activity. From these results, it is concluded that the early season pattern of isoprene emission is controlled by prevailing temperature and its interaction with developmental processes. The late-season pattern is determined by controls over leaf nitrogen concentration, especially the depletion of leaf nitrogen during senescence. Following early-season induction, isoprene emission rates correlate with photosynthesis rates. During the season there is little acclimation to temperature, so that seasonal modeling simplifies to a single temperature-response algorithm.     

Water storage in the wood and xylem cavitation in 1-year-old twigs of Populus deltoides Bartr.

The possible role of water expelled from cavitated xylem conduits in the rehydration of water-stressed leaves has been studied in one-year-old twigs of populus deltoides Bartr. Twigs were dehydrated in air. At desired values of leaf water potential (Ψ_l) (between near full turgor and -1.62 MPa), twigs were placed in black plastic bags for 1–2h. Leaf water content was measured every 3–5 min before bagging and every 10 min in the dark. Hydraulic conductivity and xylem cavitation were measured both in the open and in the dark. Cavitation was monitored as ultrasound acoustic emissions (AE). A critical Ψ_l value of -0.96 MPa was found, at which AE increased significantly while the leaf water deficit decreased by gain of water. Since the twigs were no longer attached to roots, it was concluded that water expelled from cavitated xylem conduits was transported to the leaves, thus contributing to their rehydration. Xylem cavitation is discussed in terms of a ‘leaf water deficit buffer mechanism’, under not very severe water stress conditions.     

Stress-induced changes in carbon sources for isoprene production in Populus deltoides

Isoprene is emitted from leaves of numerous plant species and has important implications for plant metabolism and atmospheric chemistry. The ability to use stored carbon (alternative carbon sources), as opposed to recently assimilated photosynthate, for isoprene production may be important as plants routinely experience photosynthetic depression in response to environmental stress. A CO₂‐labelling study was performed and stable isotopes of carbon were used to examine the role of alternative carbon sources in isoprene production in Populus deltoides during conditions of water stress and high leaf temperature. Isotopic fractionation during isoprene production was higher in heat‐ and water‐stressed leaves (?8.5 and ?9.3‰, respectively) than in unstressed controls (?2.5 to ?3.2‰). In unstressed plants, 84–88% of the carbon in isoprene was derived from recently assimilated photosynthate. A significant shift in the isoprene carbon composition from photosynthate to alternative carbon sources was observed only under severe photosynthetic limitation (stomatal conductance < 0.05 mol m^?2 s^?1). The contribution of photosynthate to isoprene production decreased to 77 and 61% in heat‐ and water‐stressed leaves, respectively. Across water‐ and heat‐stress experiments, allocation of photosynthate was negatively correlated to the ratio of isoprene emission to photosynthesis. In water‐stressed plants, the use of alternative carbon was also related to stomatal conductance. It has been proposed that isoprene emission may be regulated by substrate availability. Thus, understanding carbon partitioning to isoprene production from multiple sources is essential for building predictive models of isoprene emission.     

An integrated genetic map of Populus deltoides based on amplified fragment length polymorphisms

Amplified fragment length polymorphism (AFLP) is an efficient molecular technique for generating a large number of DNA-based genetic markers in Populus. We have constructed an integrated genetic map for a Populus backcross population derived from two selected P. deltoides clones using AFLP markers. A traditional strategy for genetic mapping in outcrossing species, such as forest trees, is based on two-way pseudo-testcross configurations of the markers (testcross markers) heterozygous in one parent and null in the other. By using the markers segregating in both parents (intercross markers) as bridges, the two parent-specific genetic maps can be aligned. In this study, we detected a number of non-parental heteroduplex markers resulting from the PCR amplification of two DNA segments that have a high degree of homology to one another but differ in their nucleotide sequences. These heteroduplex markers detected have served as bridges to generate an integrated map which includes 19 major linkage groups equal to the Populus haploid chromosome number and 24 minor groups. The 19 major linkage groups cover a total of 2,927 cM, with an average spacing between two markers of 23. 3 cM. The map developed in this study provides a first step in producing a highly saturated linkage map of the Populus deltoides genome. Received: 10 September 1999 / Accepted: 3 November 1999     

Ecological and evolutionary aspects of isoprene emission from plants

Isoprene (2-methyl-1,3,-butadiene), produced by many woody and a few herbaceous plant species, is the dominant volatile organic compound released from vegetation. It represents a non-trivial carbon loss to the plant (typically 0.5–2%, but much higher as temperatures exceed 30°C), and plays a major role in tropospheric chemistry of forested regions, contributing to ozone formation. This review summarizes current knowledge concerning the occurrence of isoprene production within the plant kingdom, and discusses other aspects of isoprene biology which may be of interest to the ecological community. The ability to produce significant amounts of isoprene may or may not be shared by members of the same plant family or genus, but emitting species have been found among bryophytes, ferns, conifers and Ephedra and in approximately one-third of the 122 angiosperm families examined. No phylogenetic pattern is obvious among the angiosperms, with the trait widely scattered and present (and absent) in both primitive and derived taxa, although confined largely to woody species. Isoprene is not stored within the leaf, and plays no known ecological role as, for example, an anti-herbivore or allelopathic agent. The primary short-term controls over isoprene production are light and temperature. Growth in high light stimulates isoprene production, and growth in cool conditions apparently inhibits isoprene, production of which may be induced upon transfer to warmer temperatures. The stimulation of isoprene production by high irradiance and warm temperatures suggests a possible role in ameliorating stresses associated with warm, high-light environments, a role consistent with physiological evidence indicating a role in thermal protection. Received: 1 April 1998 / Accepted: 9 November 1998     

杨树受机械损伤与光肩星天牛危害的防御性反应

杨树是我国“三北”地区防护林建设的主栽树种,自20世纪70年代以来长期受到光肩星天牛的严重危害。北抗杨对光肩星天牛有一定的抗性,但产生抗性的生化机制尚不清楚。本研究采用试剂盒法与高效液相色谱法以未受害、机械损伤、虫害北抗杨为研究材料,对其树皮和木质部中的次生代谢产物和防御酶含量进行检测,以探索其抗性机制。结果表明,北抗杨受到机械损伤和光肩星天牛危害后其反应不同:1)次生代谢产物,北抗杨受到机械损伤后,树皮中的水杨苷和白杨甙含量显著上升,槲皮苷含量降低;而受光肩星天牛危害后,树皮中的水杨苷和槲皮苷含量显著上升,白杨甙含量无显著变化。机械损伤的北抗杨木质部总酚含量高于虫害与未受害木质部,后两者间无显著差异;光肩星天牛危害的北抗杨木质部白杨甙和亚麻木酚素含量高于机械损伤木质部与未受害木质部。遭受机械损伤与虫害后北抗杨木质部的总酚苷含量显著高于未受害木质部。2)防御酶活性分析表明,与未受害北抗杨树皮相比,受到机械损伤与虫害后的树皮苯丙氨酸解氨酶(PAL)活性显著升高,但两者间无差异;受到机械损伤与虫害后的树皮超氧化物歧化酶(SOD)活性高于未受害树皮,且机械损伤树皮高于虫害树皮;北抗杨受机械损伤与虫害后木质部中的过氧化物酶(POD)活性高于未受害木质部,但两者间无差异。3)与未受害北抗杨相比,北抗杨受机械损伤、虫害后部分次生代谢物和防御酶都有不同程度的增加,推测这些物质可能与北抗杨抗逆性反应有关。     

Water stress,temperature, and light effects on the capacity for isoprene emission and photosynthesis of kudzu leaves

Kudzu (Pueraria lobata (Willd) Ohwi.) is a vine which forms large, monospecific stands in disturbed areas of the southeastern United States. Kudzu also emits isoprene, a hydrocarbon which can significantly affect atmospheric chemistry including reactions leading to tropospheric ozone. We have studied physiological aspects of isoprene emission from kudzu so the ecological consequences of isoprene emission can be better understood. We examined: (a) the development of isoprene emission as leaves developed, (b) the interaction between photon flux density and temperature effects on isoprene emission, (c) isoprene emission during and after water stress, and (d) the induction of isoprene emission from leaves grown at low temperature by water stress or elevated temperature. Isoprene emission under standard conditions of 1000 mol photons·m^-2·s^-1 and 30°C developed only after the leaf had reached full expansion, and was not complete until up to two weeks past the point of full expansion of the leaf. The effect of temperature on isoprene emission was much greater than found for other species, with a 10°C increase in temperature causing a eight-fold increase in the rate of isoprene emission. Isoprene emission from kudzu was stimulated by increases in photon flux density up to 3000 mol photons·m^-2·s^-1. In contrast, photosynthesis of kudzu was saturated at less than 1000 mol·m^-2·s^-1 photon flux density and was reduced at high temperature, so that up to 20% of the carbon fixed in photosynthesis was reemitted as isoprene gas at 1000 mol photons·m^-2·s^-1 and 35°C. Withholding water caused photosynthesis to decline nearly to zero after several days but had a much smaller effect on isoprene emission. Following the relief of water stress, photosynthesis recovered to the prestress level but isoprene emission increased to about five times the prestress rate. At 1000 mol photons·m^-2·s^-1 and 35°C as much as 67% of the carbon fixed in photosynthesis was reemitted as isoprene eight days after water stress. Leaves grown at less than 20°C did not make isoprene until an inductive treatment was given. Inductive treatments included growth at 24°C, leaf temperature of 30°C for 5 h, or witholding water from plants. With the new information on temperature and water stress effects on isoprene emission, we speculate that isoprene emission may help plants cope with stressful conditions.     

美洲黑杨不同无性系对分月扇舟蛾幼虫的抗性及相关机理

为了选育出在生产上具有推广价值的美洲黑杨Populus deltoides优良抗虫品系,本研究以分月扇舟蛾Clostera anastomosis 3龄幼虫为材料,以I-72杨为对照评价和分析了18个美洲黑杨无性系在实验室条件（28±1℃,RH 70%,16L∶8D）下的抗虫性,通过选择性和非选择性取食实验筛选出了11个具有较强抗性的无性系; 测定了美洲黑杨主要营养物质和次生代谢物质含量,研究了不同无性系对分月扇舟蛾体内保护酶和消化酶活性及对该虫生长发育和食物利用的影响。结果表明：美洲黑杨不同无性系抗性的大小与它们叶片中总酚含量呈明显正相关趋势; 抗性水平不同的无性系对分月扇舟蛾幼虫的生长发育和食物利用有不同的影响,表现在幼虫体重、每日体重增加量、相对生长率、近似消化率、食物利用率和食物转化率等主要生长发育指标的变化上,同时对分月扇舟蛾幼虫取食量和排粪量亦有不同的影响。结果说明,分月扇舟蛾对次生代谢物质的反应更为敏感,抗性无性系对分月扇舟蛾幼虫体内SOD和CAT酶活性有明显的激活作用。     

On the relationship between isoprene emission and photosynthetic metabolites under different environmental conditions

Isoprene emission is related to photosynthesis but the nature of the relationship is not yet known. To explore this relationship we have examined the rate of isoprene emission, photosynthesis, and the contents of photosynthetic metabolites in leaves of velvet bean (Mucuna deeringeniana L.) and red oak (Quercus rubra L.) in response to a light-to-dark transition and to changes in air composition. Isoprene emission fell when darkness was imposed and the drop was associated with reduced amounts of ribulose-1,5-bisphosphate and ATP. The rate of isoprene emission and ATP content were reduced to the same extent by exposure to low O₂ or high CO₂ partial pressures. Only when O₂ and CO₂ were simultaneously removed from the air did the rate of isoprene emission drop without a corresponding change in ATP. The results demonstrate that when carbon is not limiting, isoprene emission is highly correlated with ATP content. When synthesis of phosphoglyceric acid is inhibited, however, carbon availability may control isoprene production. Mr. Peter Vanderveer assisted with the measurements of enzymatic metabolites. Mr. Xavier Socias is gratefully acknowledged for Rubisco preparation. This research was supported by the U.S. National Science Foundation, grant no. IBN 9105274.     

I-69杨竞争密度效果分析

用竞争密度效果的倒数式分析了I－69杨（Populus deltoids）的生长过程。随着时间的推移,C－D线在双对数图上向上移动。生物时间τ（τ被定义为逻辑斯蒂生长曲线中生长系数λ（t）的积分）与物理时间t的关系可以用双曲线方程表示。C－D效果倒数式（即1／w＝Aρ＋B,式中w和ρ分别代表平均单株材积和密度）中的系数A和B被求出。随着生物时间τ的增加,系数A急剧增另到最大值后逐渐下降。而系数B呈指数下降,倾向于接近零。随着林分的生长,生长系数λ（t）倾向于下降。