风沙干扰在濒危植物沙生柽柳群落形成演变过程中的作用

风沙干扰影响沙生柽柳(Tamarix taklamakanensis M.T.Liu)群落形成、发展和衰亡的全过程。经8年的调查、试验和探索后认为,沙生柽柳群落形成于低湿风蚀洼地,发展于沙埋地,死亡于风蚀地和重度沙埋地。在群落形成初期,风蚀形成的洼地为沙生柽柳种子发芽生根创造了适宜的生境,但高矿化度水胁迫使得沙生柽柳幼苗保存率较低;在群落发展期,沙埋促使沙生柽柳灌丛茁壮生长;在群落衰落期,风蚀或沙埋导致沙生柽柳灌从消亡。即在沙生柽柳群落的形成发展过程中,风沙干扰具有促进作用;而在沙生柽柳群落的衰落过程中,风沙干扰则具有加速衰亡的作用。此外,结合沙生柽柳生境分析认为,在高干扰和高胁迫情况下,荒漠地区耐胁迫的沙丘先锋植物仍可以生存,这一结果是对CSR对策的补充。     

RNA干扰在植物中的作用机理及其应用研究进展

RNA干扰(RNAi)是广泛存在于生物中的一种现象,它是小干扰RNA诱导的转录后基因沉默,是生物抵抗异常DNA的一种保护机制,同时在生物生长发育过程中调控基因的表达.本文综述了近年来有关RNA干扰的发现、作用过程及其机理,分析了它与反义寡核苷酸、核酶、脱氧核酶的小同,并介绍了RNA干扰在植物基因功能、植物抗病毒、作物品种改良等方面的应用,为siRNA干扰的进一步利用提供参考资料.     

中国东北样带草地群落放牧干扰植物多样性的变化

放牧干扰是草地群落植物多样性变化的主要影响因素之一。中国东北样带9个草地群落放牧干扰植物多样性变化的研究结果表明：中牧或重牧阶段Shannon指数达最大值,形成中牧（重牧）>重牧（中牧）>轻牧>过牧的规律。群落物种丰富度、均匀度与多样性的相关分析表明,均匀度变化对多样性变化具有更大的贡献率,而丰富度呈下降趋势,即轻牧（中牧）>中牧（轻牧）>重牧>过牧。生活型功能群多样性也表现出明显的变化。中国东北样带草地群落植物多样性的分布格局是：草甸草原>典型草原>典型草原 >荒漠草原>碱化草原,并且群落物种丰富度对多样性有更大贡献率。     

大沙鼠在柽柳沙包“肥岛”形成过程中的作用

灌木"肥岛"的形成和维持是物理和生物过程共同作用的结果。植物是影响灌木"肥岛"形成的关键因素;动物活动亦能影响土壤的理化性质,促进"肥岛"的形成。本文以中亚干旱区的代表性物种"柽柳"和"大沙鼠"为研究对象,研究了大沙鼠活动对柽柳沙包"肥岛"效应的影响。结果表明:无大沙鼠定居的柽柳沙包具有"肥岛"效应,但土壤养分含量并无显著提高;大沙鼠定居后,柽柳沙包出现明显的"肥岛"效应,土壤养分含量显著高于丘间对照地;大沙鼠活动促进了15～50cm深层土壤养分的富集,速效氮含量甚至是相同深度无洞柽柳沙包的2倍以上。表明大沙鼠活动促进了柽柳沙包"肥岛"的形成。     

RNA干扰及其在植物代谢工程中的应用

RNA干扰(RNA interference,RNAi)是一种高效的、序列特异的基因沉默现象。本文介绍了RNA干扰的发现及其干扰机制,阐明RNA干扰可在发现代谢途径中的新基因并验证其功能、改善植物营养价值、提高植物抗性、创造新种质等方面发挥重要作用。     

内蒙古羊草草原植物种能量含量及其在群落中的作用

根据11a的野外实验对内蒙古羊草草原群落42种植物的能量含量（含灰分）及其在群落中的相对生物量进行了研究。不同植物种地上部分的能量含量在（13156±1141）J／g和（18141±527）J／g之间变动,所有物种的平均能量含量为（16899±840）J／g,种间变异系数4．9％。小叶锦鸡儿具有最高的能量含量。禾草的平均能量含量高于杂草。根据生活型和生长型,草本物种被进一步分组,能量含量从高到低的排列顺序为：高禾草（17717±92）J／g〉豆科植物（17228±433）J／g〉矮禾草（17250±218）J／g〉其余杂草（16784±529）J／g〉半灌木（16719±69）J／g〉1、2年生植物（15911±1759）J／g。42种植物的能量含量和它们在群落中的相对生物量存在显著正相关关系。根据它们在群落中的构成比例进行分组,以物种在群落中的相对生物量为权重,各组能量含量依次为：优势种（17740J／g）〉伴生种（17244J／g。）〉偶见种（16653J／g）。高能量含量的植物更具竞争力,在群落中通常占据优势地位,而低能量含量的植物竞争力通常较弱,构成草原群落的伴生种或偶见种。     

微RNA在植物抗逆过程中的作用

微RNA（microRNA,miRNA）通过降解靶基因的mRNA或者抑制其靶基因的翻译控制生物体的多项重要生物途径,影响生物体不同组织器官的发育。本文重点综述了与植物抗逆相关的miRNA的最新研究进展。     

从种间联结分析濒危植物毛柄小勾儿茶在群落中的地位

毛柄小勾儿茶 (Berchemiellawilsoniivar.pubipetiolata) 为我国分布于浙江、安徽局部地区的特有珍稀物种, 由于自身和人为干扰的原因, 该种受到灭绝威胁。该文在 2× 2联列表基础上, 应用 χ2 检验、联结系数 (AC) 分别检测了毛柄小勾儿茶在 4个分布点与群落中乔、灌两层植物的种间联结性。综合比较 χ2 检验与AC值的测定结果, 在 4个分布点, 毛柄小勾儿茶与群落中其它种群的关联情况十分相似 :1) 绝大多数种群与毛柄小勾儿茶的AC值在 - 0.2至 0.2之间, 即无关联 ;2 ) 与毛柄小勾儿茶存在显著关联的种群仅有一个或无 ;3) 优势种群与毛柄小勾儿茶关联小。这说明 4个分布点毛柄小勾儿茶在群落中都具有很大的独立性或随机性, 它只是群落的伴生种或偶见种。研究结果对为该物种制定合适的就地保护措施和恢复计划具有参考价值。     

多胺在植物生长发育过程中的生理作用

多胺在植物生长发育过程中具有广泛的生理作用,如参与植物衰老进程的调控、体细胞胚发生、花芽分化、花和果 实的发育及参与各种生理胁迫反应等。本文重点综述了多胺在植物生长发育过程中生理学功能方面的研究进展,并对有关 问题进行了讨论和展望。     

内源小RNAs在植物病原体抗性反应中的作用

内源小RNAs是动植物基因表达的重要调节分子,它们可以通过指导mRNA的降解、抑制翻译或染色体修饰等机制,在转录水平或转录后水平或两个水平沉默基因.内源小RNAs在植物生长发育和生物和非生物胁迫适应反应中具有重要作用,其中3种内源性的小RNAs参与了植物基本免疫反应和对病原体的特异性免疫反应.内源小RNAs的发现为植物抗菌和抗病研究开辟了新思路,就这几种内源性的小RNAs的产生和它们在植物抗病原体反应中的作用做一概述.     

The influences of surface water-overflowing disturbance on the fluctuations of Tamarix ramosissima community in Western China

The main purpose of this study is to examine the fluctuation characteristics of Tamarix ramosissima community from the year of 2007–2008 in desert riparian forest under human surface water-overflowing disturbance in the lower reaches of Tarim River, China. In this paper, community structure, species diversity and dominant species were chosen as the indicators which could reflect the characteristics of community fluctuation. The representative sampling method was used to investigate and measure the fluctuation process of Comm. T. ramosissima. The main results showed that species numbers of the community increased 66.7% under the surface water-overflowing disturbance within two years comparing with it under non-disturbance. The Sorensen similarity coefficient of plant species is 0.75 in community under the disturbance and non-disturbance, indicating that species composition is very similar and main structure of the community has not changed on these two different treatments. Species diversity index of Comm. T. ramosissima changed a lot under the disturbance. Compared with it under non-disturbance, species richness and species diversity have been increasing while species evenness declined slightly under the disturbance. The numbers and kinds of dominant species also changed in community under the disturbance, of which the dominance of T. ramosissima is significantly increased. Compared with the river channel water disturbance, surface water-overflowing disturbance could enhance seed germination and plant growth through the effect of shallow soil moisture and its physic-chemical properties. And it improved the germination of plant seed in the soil and promoted the clone growth of plant reproductive body. As a result, species diversity was increased and species composition happened significantly changed in Comm. T. ramosissima influenced by the water-overflowing disturbance. In addition, community hierarchical structure was getting more complex. And then, it was concluded that water-overflowing disturbance is an effective way to positively affect the fluctuation of Comm. T. ramosissima in the lower reaches of Tarim River. Thus, it can make up for the insufficient effectiveness of river channel water disturbance to restore damaged vegetation.     

Vegetation Response Following Invasive Tamarisk (Tamarix spp.) Removal and Implications for Riparian Restoration

Using a retrospective study of tamarisk removal sites across five states in the southwestern United States, we investigated (1) decreases in tamarisk cover; (2) the effects of tamarisk removal on vegetation; and (3) whether cutting or burning tamarisk has differing effects on plant communities. Our study provides an important first step in recognizing the effects of removing a dominant invasive species on meeting long-term goals of riparian restoration. We found that (1) both cutting and burning reduced mean tamarisk foliar cover by 82–95%, and this reduction was sustained over time. (2) Native foliar cover was 2- to 3-fold higher on tamarisk removal sites, but total foliar cover remained 60–75% lower than on control transects. No trend toward increases in native cover was noted over time. When tamarisk was included in the analyses, diversity in tamarisk removal sites was 2- to 3-fold higher than in the control sites and vegetation communities differed between treated and untreated sites. When tamarisk was excluded from the analyses, diversity was not greater at tamarisk removal sites, and there were no community differences between the treated and untreated transects. Differences in diversity were found to be driven by differences in evenness; overall species richness did not change following tamarisk removal. Sites in the Mojave showed the strongest increase in native foliar cover and diversity, Chihuahuan-transition sites showed a slight increase, and sites on the Colorado Plateau showed no overall increase. (3) There were no differences between plant communities at burned and cut sites. Our research indicates that vegetation response to tamarisk removal is often negligible. Land managers should be prepared for persistent depauperate plant communities following tamarisk removal if additional restoration measures are not instigated.     

柽柳胚和胚乳发育的观察

利用常规石蜡制片技术,对柽柳（Tamarix chinensis Lour.）胚和胚乳的发育过程进行了观察。结果表明,胚发育属茄型,其基细胞先行纵裂。胚柄基部发育迅速,具吸器作用,球形胚期胚柄最为发达,其细胞质丰富,贮藏淀粉类物质,至晚心形胚期胚柄依然存在。助细胞被受精产生多胚现象。胚乳发育属核型,初生胚乳核常常晚于合子分裂,胚乳核的分裂速度慢于胚体细胞的分裂速度。当胚乳游离核为 32个时,以自由生长细胞壁的方式进行胚乳细胞化。胚乳细胞进一步增殖极少。珠心细胞只有两层,细胞核大,胞质丰富,内含贮藏物质,至心形胚期逐渐解体。     

Minireviews: Neighborhood Effects, Disturbance Severity, and Community Stability in Forests

A theoretical framework and conceptual model for temporal stability of forest tree-species composition was developed based on a synthesis of existing studies. The model pertains primarily to time periods of several tree lifetimes (several hundred to a few thousand years) at the neighborhood and stand spatial scales (0.01–10 ha), although a few extensions to the landscape scale are also made. The cusp catastrophe was chosen to illustrate compositional dynamics at the stand level for jack pine, northern hardwood, and white pine forests in the Great Lakes Region of the United States and for tropical rainforests in the northern Amazon basin. The models feature a response surface (degree of dominance by late-successional species) that depends on two variables: type of neighborhood effects of the dominant tree species and severity of disturbances. Neighborhood effects are processes that affect the chance of a species replacing itself at the time of disturbance (they can be positive, neutral, or negative) and are of two types: overstory–undestory effects, such as the presence of advanced reproduction; and disturbance-activated effects, such as serotinous seed rain. Disturbance severity is the proportion of trees killed during a disturbance. Interactions between neighborhood effects and disturbance severity can lead to either punctuated stability (dramatic but infrequent change in composition, in those forests dominated by species with positive neighborhood effects) or succession (continuous change, in those forests dominated by species with neutral-negative neighborhood effects). We propose that neighborhood effects are a major organizing factor in forest dynamics that provide a link across spatial scales between individual trees and disturbance/patch dynamics at the stand and landscape scales. Received 23 June 1998; accepted 16 December 1998.     

The influences of surface water-overflowing disturbance on the fluctuations of Tamarix ramosissima community in Western China

The main purpose of this study is to examine the fluctuation characteristics of Tamarix ramosissima community from the year of 2007–2008 in desert riparian forest under human surface water-overflowing disturbance in the lower reaches of Tarim River, China. In this paper, community structure, species diversity and dominant species were chosen as the indicators which could reflect the characteristics of community fluctuation. The representative sampling method was used to investigate and measure the fluctuation process of Comm. T. ramosissima. The main results showed that species numbers of the community increased 66.7% under the surface water-overflowing disturbance within two years comparing with it under non-disturbance. The Sorensen similarity coefficient of plant species is 0.75 in community under the disturbance and non-disturbance, indicating that species composition is very similar and main structure of the community has not changed on these two different treatments. Species diversity index of Comm. T. ramosissima changed a lot under the disturbance. Compared with it under non-disturbance, species richness and species diversity have been increasing while species evenness declined slightly under the disturbance. The numbers and kinds of dominant species also changed in community under the disturbance, of which the dominance of T. ramosissima is significantly increased. Compared with the river channel water disturbance, surface water-overflowing disturbance could enhance seed germination and plant growth through the effect of shallow soil moisture and its physic-chemical properties. And it improved the germination of plant seed in the soil and promoted the clone growth of plant reproductive body. As a result, species diversity was increased and species composition happened significantly changed in Comm. T. ramosissima influenced by the water-overflowing disturbance. In addition, community hierarchical structure was getting more complex. And then, it was concluded that water-overflowing disturbance is an effective way to positively affect the fluctuation of Comm. T. ramosissima in the lower reaches of Tarim River. Thus, it can make up for the insufficient effectiveness of river channel water disturbance to restore damaged vegetation.     

退化植物群落结构及其物种组成在人为干扰梯度上的响应

在岷江上游大沟流域,沿着人为干扰梯度,调查了退化榛栎群落的结构及其物种组成变化。结果表明：（１）除密度外,群落木本层的结构特性（密度、高度、生物量、基径面积和物种多样性）与干扰强度的增加呈负相关,而其草本物种多样性、生态优势度呈正反应,但地上生物量变化呈现相反的趋势;（２）根据群落内植物种群密度（或盖度）在干扰梯度上的响应变化,群人４７个种可基本上分成３个反应种组：１６个为扩展种（ｉｎｖａｓｉｖｅ     

塔里木河中游地区柽柳对地下水埋深的生理响应

以塔里木河中游沙吉力克断面和阿其河断面的柽柳为研究对象,结合两断面地下水埋深的动态监测和柽柳叶片可溶性糖、脯氨酸、MDA含量及SOD、POD活性等生理指标的分析测试,研究了不同地下水埋深与柽柳生理变化的关系,以探讨该地区柽柳的抗旱机理与受胁迫程度.研究表明:随着地下水埋深的不断增加,柽柳叶片的可溶性糖含量、脯氨酸含量、MDA含量和SOD活性均显著增加,而POD活性则呈不断下降的趋势,并且柽柳各生理代谢相互协调;地下水埋深与柽柳叶片的可溶性糖、脯氨酸、MDA含量以及SOD活性呈正相关,相关系数分别为0.602*、0.548、0.735**和0.829**,与POD活性呈负相关(r=-0.709**).研究发现,塔里木河中游地区柽柳的生长已受到严重的干旱胁迫,且沙吉力克断面的柽柳所受到的干旱胁迫较重;柽柳在一定范围内能通过调节体内渗透调节物质的含量和保护酶活性来积极响应地下水埋深的变化,以增强植株自身抗旱能力.     

基于转录组的阿拉善地区多枝柽柳多态Genic-SSRs的识别与开发

基因内部的简单重复序列(Genic-SSR)可在植物适应环境变化中发挥重要作用。通过对阿拉善5个样点多枝柽柳(Tamarix ramosissima)的转录组进行测序、组装和比较,经CandiSSR软件分析,共鉴定出代表157个基序类型的1 185个多态性Genic-SSR位点,位于1 123个转录本中。其中,三核苷酸...     

Isolation and characterization of 10 polymorphic microsatellites in saltcedars (Tamarix chinensis and Tamarix ramosissima)

Tamarix ramosissima and Tamarix chinensis are invasive weed species in western North America. Previous studies based on single locus DNA sequence data revealed some information about the invasion process, but multilocus markers can provide additional information about levels of introgression and genotype origins. We have developed primers that amplify 10 polymorphic microsatellite loci from T. ramosissima; these primer pairs also successfully amplify polymorphic microsatellites from the closely related T. chinensis, a species that forms hybrids with T. ramosissima in the western USA.