Transcriptome and degradome sequencing reveals changes in Populus×euramericana‘Neva’caused by its allelopathic response to p-hydroxybenzoic acid

Plant species produce different types of allelopathic chemicals in nature;however,little is known about the differential regulation of plant allelopathy.Because allelopathy caused by p-hydroxybenzoic acid(pHBA)is one of the main obstacles to continuous cropping of Populus×euramericana ‘Neva’,we examined gene expression dynamics in Neva leaves induced by pHBA.The expression of genes related to photosynthesis and respiration changed,while mRNA involved in regulating gene expression during allelopathy was degraded.Some miRNAs that are involved in plant allelopathy target crucial genes for regulating reactive oxygen species.Moreover,coexpression regulatory networks were constructed based on profiles of the identified miRNA-target interactions and the differentially expressed miRNA-target pairs.These findings provide a mechanistic framework for understanding allelopathy in plants.

Absorption and Accumulation of Heavy Metal from Soil by Leaves of Populus x euramericana cv.‘Neva’Plantation

The absorption and enrichment of heavy metal elements by leaves of Populus×euramericana cv.’Neva’ were analyzed through content assessing of heavy metal elements in soils of three forest lands at Fangshan District in the southern suburb of Beijing. These forest lands with P.×euramericana cv. ’Neva’plantation were around with the various sources of pollution such as cement mill,stone mill, sewage and garbage.Some of heavy metal elements such as Cd,Pb,Cu,and Zn were found in the soil samples and leaves of P.×euramericana cv.’Neva’ grown on the three forest lands which were investigated.The results of investigation showed that the soils of three forest lands were polluted with Pb, Cd,Cu and Zn in varying degrees.The contents of Pb,Cu and Zn in soils were significantly different among the three forest lands,whereas the average content of Cd(0.077 6 mg·kg-1) was less but that of Pb,Cu,and Zn(37.61,26.25 and 90.3 mg·kg-1 ) were more than the average background value of Beijing.The contents of Pb,Cd,Cu and Zn in leaves of P.×euramericana cv.’Neva’ were different among three forestlands.With the changes of heavy metal contents in soil samples,there was no regularity on the changes of different heavy metal contents in leaves of P.×euramericana cv.’Neva’ grown on different forest land.P.×euramericana cv.’Neva’ can absorb and accumulate Pb,Cd,Cu and Zn in soil but showed different capacities of absorption and accumulation with the order of Cd】Zn】Cu】Pb.Especially,its absorption and accumulation capacity for Cd was strong with maximum enrichment factor higher than 16 and showed high accumulation on low background,whereas its enrichment capacities for Pb and Cu were relatively poorer with average enrichment factor of less than 1.At different forest lands,there existed great difference on absorption capacity of P.×euramericana cv.’Neva’ with the same heavy metal.

Establishment of Efficient Regeneration System of Populus×euramericana cl.‘Bofeng’

Compared with the species of Leuce section,the difficulty in plant regeneration during tissue culture for the species of Aigeiros section is a key limiting factor for their application in genetic engineering of forest trees.In this study,the plant growth regulators combination,copper concentration,light intensity,and the selection pressures of kanamycin were investigated using leaves of Populus×euramericana cl.’Bofeng’ as explants,and a stable and high efficient regeneration system was established.Using this system,both the shoot regeneration rate and rooting rate were up to 100%,and the average number of differentiated shoots in each leaf explant was up to 20,and the survival rate of seedlings reached 98%.The optimal selection pressure of kanamycin in shoot inducement for leaf-explant was 40 mg·L-1,and the optimal selection pressure of kanamycin in root inducement of adventitious bud was 20 mg·L-1.The authors also found that differentiation rate of adventitious buds of P.×euramericana cl.’Bofeng’ could be significantly promoted by increased copper concentration,and this is the first report about the key role of copper（Cu） in explant regeneration of Poplars.This regeneration system with high frequency which was established by the authors was as good as that of species of Leuce section,and it provides a good technological platform for genetic engineering of forest tree which uses the species of Aigeiros section as model materials.

Tissue Culture Technology for Populus × euramericana Hybrids: Effect of Genotype on in Vitro Regeneration

In order to select a suitable genotype for the studies on genetic transformation, the difference among three genotypes (DN04-18, DN04-25 and DN04-26) of Populus × euramericana (Populus deltoides × P. nigra) in terms of shoot regeneration was investigated in this paper. An efficient in vitro micropropagation method was successfully established for genotype DN04-18. The high frequency shoot regeneration (90.0%) from leaf discs was obtained in genotype DN04-18 on the modified Murashige and Skoog (mMS) medium with 30 g/L sucrose and 5.5 g/L agar (pH: 5.8) which was supplemented with 0.8 mg/L 6-benzyladenine (6-BA), while the shoot regeneration rates of DN04-25 and DN04-26 were below 40.0% even on the same medium. The optimum rooting medium was 1/2 mMS medium supplemented with 0.3-0.4 mg/L indole-3-butyric acid (IBA) for three genotypes. The results showed that genotype is a key factor for restricting shoot regeneration in establishing regeneration system of P. × euramerican hybrids. This micropropagation system of DN04-18 is expected to be suitable for the studies on gene transformation to improve drought tolerance of P. × euramerican.

‘中红’杨芽变枝条叶片成熟过程中黄酮类物质变化规律

从代谢物质变化的角度,探寻‘中红’杨(Populus euramericana‘Zhonghuahongye’)芽变叶片在成熟过程中的变化规律。以表现为绿叶的‘中红’杨芽变枝条叶片为试材,对叶片由幼嫩到成熟不同时期的代谢物进行测定和代谢组分析。在G1 VS G2组合中,检测到64种差异代谢物,包含26种上调差异表达代谢物,38种下调差异表达代谢物。在G1 VS G3组合中,检测到80种差异代谢物,包含38种上调差异表达代谢物,42种下调差异表达代谢物。在G2 VS G3组合中,检测到43种差异代谢物,包含21种上调差异表达代谢物,22种下调差异表达代谢物。差异代谢物均显著富集在黄酮和黄酮醇的生物合成途径中。代谢物发生差异的主要途径为异黄酮生花色苷物合成(ko00944)、黄酮类生物合成(ko00941)、黄酮和黄酮醇的生物合成(ko00943)、花色苷生物合成(ko00942)。叶片幼叶至变成熟叶片过程中化合物变化多样,其中最重要的就是黄酮类化合物,其他化合物辅助叶片成熟。

Effects of torrefied wood chip and vermicompost application on vegetation growth and nutrient uptake in the Saemangeum reclaimed land

Background:In reclaimed land,the growth environment for plants may be unfavorable and the initial establishment and growth of seedlings could be limited because of low nutrient and water availability.Fertilization and control of understory vegetation that competes with seedlings may be of help in ameliorating soil physical and chemical properties,resulting in better seedling growth and reclamation success.However,the amount of nutrients understory vegetation absorbs in this ecological process has been rarely studied.Thus,we aimed to investigate the effect of soil amendment on biomass production and nutrient uptake by weeds in the nutrient-poor reclaimed area.We applied three levels of torrefied wood chip(TWC;0,2.5,and 5 Mg ha^(−1))and two levels of vermicompost(VC;0 and 2.7 Mg ha^(−1))as soil physical improvements and organic soil amendments in reclaimed land in the Republic of Korea,with Populus euramericana used as the crop tree.Results:TWC did not influence weed biomass,but 2.7 Mg ha^(−1) VC significantly increased weed biomass by 21%compared to 0 Mg ha^(−1) VC treatments.Nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),magnesium(Mg),and sodium(Na)concentrations in weeds were the highest in control,but there was no statistical difference among treatments.However,VC treatment did marginally increase nutrient uptake in weeds,especially P,K,Ca,and Na.No treatments influenced crop tree height.Conclusion:We conclude that VC can be used as an organic source of nutrients in reclaimed soil and that weed management is necessary to increase treatment effects on crop trees in this salt-affected reclaimed land.

美洲黑杨×欧美杨F1无性系遗传变异和初步选择研究

为了选择对杨树细菌性溃疡病有一定抗性的优质杨树资源,于2015年在天水市进行了美洲黑杨（Populus deltoides）×欧美杨（Populus×euramericana Guinier）F1无性系遗传变异和初步选择研究的试验。本实验主要参与实验的植物为50株美洲黑杨作为母本以及50株欧美杨作为父本杂交获得25株家系以及115株F1无性系。通过3年的生长试验进行测定分析以及数据记录,数据显示美洲黑杨×欧美杨F1无性系在种源内家系间以及家系内无性系间两个不同水平上存在α为万分之一水平的显著差异,说明此试验中F1无性系具有较大的选择潜力。根据F1无性系的长势情况和对细菌性溃疡病的抗病性,选出了其中一些长势良好且对细菌性溃疡病有一定抗性的优质F1无性系,为杨树抗性引种提供了宝贵的引种材料。

‘渤丰3号’杨叶片营养诊断

为了促进杨树人工林前期的生长,需要探究施肥对杨树人工林早期生长的影响,但同时需要考虑到不同肥料之间比例的合理性。采用L_(9)(3^(4))正交试验设计方法对4年生‘渤丰3号’杨进行氮磷钾配比施肥试验,运用DRIS法对叶片进行营养诊断。结果表明:1)不同的氮磷钾配比施肥对杨树生长的影响不同,施肥后杨树生长强于和弱于不施肥杨树的现象并存。本次研究中以处理9(氮磷钾3种元素的施肥量均为最大,分别为400、120、60g/株)处理下的杨树获得了最大的生长量,树高生长量达到4.53m,胸径生长量达到5.55cm。2)本次试验中杨树叶片N、P、K、Ca、Mg等5种元素浓度的最佳比值范围是N/K=3.45±0.40、P/N=0.08±0.003、P/K=0.27±0.03、Ca/N=0.76±0.06、Ca/P=9.69±0.84、Ca/K=2.65±0.48、Mg/N=0.22±0.03、Mg/P=2.77±0.39、Mg/K=0.77±0.20、Mg/Ca=0.29±0.03;随着施肥量的增加,Ca和Mg的亏缺程度逐渐减少,因此本次建议只使用氮磷钾3种元素的需肥顺序,整体上为P>N>K。得出如下结论:氮磷钾肥料的施肥量分别为400、120、60g/株的施肥处理是该试验中的最佳施肥量,而400、120、60g/株的肥料组合还可以继续优化。