塔里木河天然胡杨林中病灶微生物的分离与形态学初探

目的:从塔里木河中下游废弃上百年的河道周围选取2处样点,采集具有不同病症胡杨的茎叶,从中进行菌种分离。方法:显微镜镜检,革兰氏染色及生理生化检测。结果:通过形态观察,得到13株细菌、4株真菌。其中的7株细菌分离于病叶,其余10株分离于病变树皮。对13株细菌革兰氏染色结果表明,2株为革兰氏阴性菌,11株为革兰氏阳性菌。对真菌的孢子形态观察表明,4株均为霉菌。结论:实验首次对胡杨特殊病灶微生物进行分类统计,为解决由微生物感染引起的胡杨林退化问题积累数据。     

铅污染对青杨雌雄幼苗铅富集和营养特征的影响

该研究以青杨雌雄幼苗为实验材料,采用盆栽控制实验的方式,设置20.5(CK)、50(T1)和100mg·kg-1(T2)3个铅浓度水平,分析面源水平铅污染条件下青杨性别间铅的积累和营养状况的差异。结果表明:(1)与CK相比,面源水平铅污染条件下,青杨雄株幼苗的总生物量未受到显著影响,雌株总生物量显著降低,但相同处理条件下雌株生物量均显著高于雄株。(2)2个梯度的铅污染均未显著影响两种性别青杨各器官中N的浓度,且雌雄间的性别差异不显著,但T2处理一定程度降低了两种性别各器官中P的浓度;与CK相比,雄株在受铅胁迫处理时N/P逐渐增加,说明此时雄株的生长可能会逐渐受到P素营养缺乏的影响。(3)随着铅处理浓度的增加,青杨雌株幼苗对铅的积累总量逐步增加,但雄株的积累总量的增加却不显著。可见,青杨雄株在面源水平铅污染条件下的抗性和耐受性优于雌株;雌雄青杨对土壤铅污染有不同的适应策略,雌株对铅的积累策略是其生物量下降以及营养平衡受到影响的主要原因,雄株对铅低吸收的策略使其更适应在铅污染区域生长。     

钙-钙调素在零下低温诱导毛白杨扦插苗抗冻性中的作用

以零下低温锻炼和结合效应剂(CaCl2、钙离子螯合剂EGTA、钙离子通道阻断剂LaCl3或钙调素拮抗剂CPZ)处理的低温锻炼下的毛白杨(Populus tomentosa)扦插苗为试材,对其体内丙.醛(M D A)及钙调素(CaM)含量,超氧化物歧化酶(SOD)、过氧化物酶(POD)及线粒体腺苷三磷酸酶(Ca2 -ATPase)活性,以及幼苗的半致死温度(LT50)分别进行测定.结果表明,低温锻炼不仅在一定程度上提高了幼苗 CaM含量,SOD、POD和线粒体Ca2 -ATPase活性,降低了MDA含量和幼苗半致死温度;而且减小了低温胁迫所引起的SOD、POD、线粒体Ca2 -ATPase活性和CaM含量的下降程度以及MDA的增加幅度,促进了胁迫后恢复过程中SOD、POD、线粒体Ca2 -ATPase活性和CaM水平的迅速回升以及MDA的下降.在低温锻炼的同时,用CaCl2处理能加强低温锻炼的效果,但这种效应可被EGTA、LaCl3或CPZ处理抑制.经或未经CaCl2处理的低温锻炼后,幼苗中CaM含量的增加有助于SOD、POD和线粒体Ca2 -ATPase活性的提高,进而对幼苗抗冻性的提高有明显的促进作用.看来,Ca2 -CaM信号系统可能参与了SOD、POD和线粒体Ca2 -ATPase活性的调节和抗冻性的低温诱导.     

A novel calcium-dependent protein kinase gene from Populus euphratica, confers both drought and cold stress tolerance

Populus species are the most important timber trees over the Northern hemisphere. Most of them are cold- and drought-sensitive except the Populus euphratica Oliv. Here, a calcium-dependent protein kinase (CDPK) gene cloned from P. euphratica, designated as PeCPK10, was rapidly induced by salt, cold, and drought stresses. The protein encoded by PeCPK10 was localized within the nucleus and cytosol, which may be important for its specific regulation in cellular functions. To elucidate the physiological functions of PeCPK10, we generated transgenic Arabidopsis plants overexpressing PeCPK10. The results showed that PeCPK10-transgenic lines experienced better growth than vector control plants when treated with drought. Stronger abscisic acid-induced promotion of stomatal closing has been showed in transgenic lines. Particularly, overexpression of PeCPK10 showed enhanced freezing tolerance. Constitutive expression of PeCPK10 enhanced the expression of several abscisic acid-responsive genes and multiple abiotic stress-responsive genes such as RD29B and COR15A. Accordingly, a positive regulator responsive to cold and drought stresses in P. euphratica is proposed.     

山杨林林分密度效应动态模拟

 本文用林窗模型研究了小兴安岭南坡山杨林林分密度动态过程,在给定林分初始条件后,模拟了林分密度、断面积、生物量、叶面积指数和生产力150年的变化。用林分密度效应的3/2法则和产量恒定法则检验模拟林分,结果表明模拟林分密度发展与理论预测相符合。通过本文的研究既检验了林窗动态模型又印证了林分密度效应理论。     

On the Cytochemistry of Cell Wall Formation in Poplar Trees

Abstract: The ultrastructure of cell walls and the mechanisms of cell wall formation are still not fully understood. The objective of our study was therefore to obtain additional fine structural details on the deposition of cell wall components during the differentiation of xylem cells in hybrid aspen ( Populus tremula L. × P. tremuloides Michx.) we used as a model tree. At the electron microscope level, PATAg staining revealed a successive deposition of polysaccharides with increasing distance from the cambium. Staining with potassium permanganate and UV microspectrophotometry showed that the cell walls were lignified, with some delay to the deposition of polysaccharides. Immunogold labelling of three lignin types in developing cell walls varied with progressive deposition of cell wall layers. Condensed lignin subunits were localized in corners of cells adjacent to the cambium prior to S1 formation, whereas non-condensed lignin subunits became labelled only in later stages - in secondary walls near cell corners and simultaneously with the completion of S1 formation. As S2 polysaccharide deposition progressed, the labelling extended towards the lumen. Labelling of peroxidases revealed their presence in cell corner regions of young xylem cells, still lacking a secondary wall, implying that peroxidases are incorporated into the developing cell wall at early developmental stages. A weak labelling of middle lamella regions and secondary walls could also be seen at later stages. The results are discussed in relation to current knowledge on the succession of polysaccharide and lignin deposition in woody cell walls.     

毛白杨叶外植体的遗传转化

参考 Horsch 等(1985)建立的叶圆片转化法,建立了一个适合于杨树的遗传转化系统。本文所用的根癌农杆菌菌株含有一个经过改建的 Ti 质粒,这个质粒载有 T-DNA 的4号基因和 CAT 基因。利用毛白杨(Popular tomentosa)的叶外植体经该菌株感染后,培养3-4个星期后,在没有外源激素的 MS_u 培养基上,从叶外植体的边缘处再生出一些不正常的苗。这种苗呈典型的畸胎芽,把这种苗从外植体上切下并转到生根培养基上,在苗的基部生成大量的愈伤组织,但并不形成根,同时在愈伤组织上产生大量的芽。气相色谱法测定内源细胞分裂素的结果表明,转化苗的异戊烯基腺苷的含量是正常苗的14倍。纸电泳结果表明,转化苗均含有特异的胭脂碱。在加有60-100μg/ml 氯霉素的培养基上,转化苗可以正常生长,而未转化的苗在培养约40天后变白死去。用酚类物质水杨酸预处理农杆菌有助于提高转化频率。     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明:水分较好的沟谷台地上生长的两种树木的叶最大水力导度(Kmax)明显大于水分较差的沟间坡地,叶水力脆弱性(P50)也较高;随树龄增加,两种树木的Kmax明显下降,但P50差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWCtlp、膨压损失点时的水势ψtlp饱和含水量时的渗透势ψsat)均大于 坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木Kmax与ψtlp呈显著正相关,P50与PV曲线参数之间存在一定的相关性,表明Kmax与抗旱性之间存在一种权衡关系,P50是反映两种树木的抗旱性特征之一.     

塔里木河源流和干流胡杨年轮生长的差异性

借助树木年轮学的方法和技术手段,通过对阿克苏河、叶尔羌河和塔里木河干流不同河段胡杨年轮样本采集,分析了塔里木河两源流与干流不同河段胡杨年轮生长特征;采用单因素方差分析方法和Kendall协同系数(W)研究了塔里木河两源流和干流不同河段胡杨年轮指数的差异性;利用突变检验和小波分析方法探讨了塔河两源流、塔河干流不同河段胡杨径向生长的周期和突变性。研究结果表明:(1)1980—2010年期间,塔里木河两源流和干流不同河段年轮宽度和年轮指数均呈下降趋势。在阿克苏河、肖夹克、沙子河口3个断面胡杨年轮宽度和年轮指数下降趋势明显,而叶尔羌河和新渠满断面的胡杨年轮宽度和年轮指数下降趋势不明显。(2)塔里木河两源流和干流不同河段的胡杨年轮生长在空间上不具有一致性(W0.5),阿克苏河断面与肖夹克、沙子河口断面,叶尔羌河与肖夹克、沙子河口断面,肖夹克与新渠满断面,新渠满与沙子河口断面之间胡杨年轮指数均具有显著的差异性(P0.05)。(3)塔里木河两源流胡杨年轮指数的突变时间与河道径流量突变时间相同或者滞后,这可能与地表水转化为地下水过程有关。(4)塔里木河两源流和干流不同河段的胡杨年轮指数变化的周期均小于其地表径流变化的周期,这可能与胡杨自身的生理特点和当地气温、水分对胡杨生长综合影响有关。本研究有助于深入了解干旱区内陆河流域胡杨生长特征变化规律,同时可为该流域胡杨资源生态保育提供参考。     

A multiyear synthesis of soil respiration responses to elevated atmospheric CO2 from four forest FACE experiments

The rapidly rising concentration of atmospheric CO₂ has the potential to alter forest and global carbon cycles by altering important processes that occur in soil. Forest soils contain the largest and longest lived carbon pools in terrestrial ecosystems and are therefore extremely important to the land–atmosphere exchange of carbon and future climate. Soil respiration is a sensitive integrator of many soil processes that control carbon storage in soil, and is therefore a good metric of changes to soil carbon cycling. Here, we summarize soil respiration data from four forest free‐air carbon dioxide enrichment (FACE) experiments in developing and established forests that have been exposed to elevated atmospheric [CO₂] (168 μL L^?1 average enrichment) for 2–6 years. The sites have similar experimental design and use similar methodology (closed‐path infrared gas analyzers) to measure soil respiration, but differ in species composition of the respective forest communities. We found that elevated atmospheric [CO₂] stimulated soil respiration at all sites, and this response persisted for up to 6 years. Young developing stands experienced greater stimulation than did more established stands, increasing 39% and 16%, respectively, averaged over all years and communities. Further, at sites that had more than one community, we found that species composition of the dominant trees was a major controller of the absolute soil CO₂ efflux and the degree of stimulation from CO₂ enrichment. Interestingly, we found that the temperature sensitivity of bulk soil respiration appeared to be unaffected by elevated atmospheric CO₂. These findings suggest that stage of stand development and species composition should be explicitly accounted for when extrapolating results from elevated CO₂ experiments or modeling forest and global carbon cycles.