毛乌素沙地游击型克隆半灌木羊柴对局部沙埋的反应

不同程度的沙埋是生长在干旱和半干旱区内陆沙丘的植物经常遭遇的事件,沙埋可以改变植物所处的生物和非生物环境条件。已有研究表明不同程度的沙埋对于植物的影响不同。轻微程度的沙埋可以增加植物高度、促进生物量的积累和新生分株的产生。如果沙埋强度不断增加,对植物的影响由正效应逐渐转变为负效应。即超过一定沙埋阈值后,沙埋会削弱植物的生长,甚至影响植物的存活。干旱和半干旱区内陆沙丘中常常生长着许多克隆植物,克隆整合常常可以缓解克隆植物分株所遭受的局部环境胁迫。根茎型克隆植物羊柴(Hedysarum laeve)是毛乌素沙地的优势半灌木之一,也是当地重要的固沙植物。为了探讨克隆整合的作用是否可以提高沙埋阈值,并有助于羊柴忍受高强度的沙埋,以其为研究对象开展了野外实验。结果表明:轻微程度的沙埋(例如沙埋深度是原始羊柴分株高的10%~20%)可以加速羊柴分株的高生长,提高叶片生物量、茎生物量以及整个地上部分的生物量。高强度的沙埋(例如沙埋深度是原始羊柴分株高的80%~100%)会削弱羊柴分株的存活和生长。在与不遭受沙埋分株相连的情况下,羊柴分株遭受沙埋的阈值高于没有分株相连的,而且在高强度的沙埋下,前者(有分株相连的遭受沙埋的分株)比后者(没有分株相连的遭受沙埋的分株)在株高增量、茎生物量、叶片生物量以及地上分株生物量上都要显著高。这暗示着克隆整合提高了羊柴遭受沙埋的阈值并有助于羊柴分株忍受高强度的沙埋。     

克隆整合对无芒雀麦(Bromus inermis)忍受沙埋能力的影响

无芒雀麦是浑善达克沙地植物群落中占优势的多年生根茎禾草。研究了克隆整合特性对无芒雀麦忍受沙埋能力的影响。结果表明,克隆整合显著提高了远端完全沙埋分株的存活,耗-益分析表明远端沙埋分株的生物量、分株数、叶片数、根茎节数和根茎总长显著受益于克隆整合,而与之相连的近端非沙埋分株却没有产生显著的损耗,并且随着沙埋程度增加时,远端沙埋分株的收益有增大的趋势。因而,克隆整合特性是无芒雀麦对严酷沙埋环境形成的重要适应对策,它能够缓解沙埋对无芒雀麦存活、生长的胁迫,提高其在半干旱沙化地区的适合度。     

克隆整合对无芒雀麦(Bromus inermis)忍受沙埋能力的影响

无芒雀麦是浑善达克沙地植物群落中占优势的多年生根茎禾草。研究了克隆整合特性对无芒雀麦忍受沙埋能力的影响。结果表明,克隆整合显著提高了远端完全沙埋分株的存活,耗-益分析表明远端沙埋分株的生物量、分株数、叶片数、根茎节数和根茎总长显著受益于克隆整合,而与之相连的近端非沙埋分株却没有产生显著的损耗,并且随着沙埋程度增加时,远端沙埋分株的收益有增大的趋势。因而,克隆整合特性是无芒雀麦对严酷沙埋环境形成的重要适应对策,它能够缓解沙埋对无芒雀麦存活、生长的胁迫,提高其在半干旱沙化地区的适合度。     

水分胁迫条件下草莓克隆分株间水分调控及其对光合功能的影响

以盆栽草莓(Fragaria×ananassa)为材料研究了水分胁迫下克隆植物草莓母株和子株间的水分调控机制及其与碳同化、光系统Ⅱ激发能分配的关系.实验材料分为匍匐茎连接和剪断两个大组,进行两步实验.第1步实验,对连接组和剪断组的所有母株控水,子株充分供水;4d后进入第2步实验,把连接组分为两小组,对其中一组充分供水子株开始控水,另一组保持不变.结果表明,土壤干旱引起母株叶片失水,并使其净光合速率和气孔导度显著降低.但是连接组中供水良好的子株能有效缓解缺水母株的水分胁迫.当供水良好的子株也开始受到干旱处理的时候,则会加剧与之相连母株的水分胁迫.受胁迫母株可以通过加强渗透调节能力和降低水势从相连子株获取水分.虽然土壤干旱会造成受胁迫母株叶片脱落酸(abscisic acid, ABA)含量的大幅度增加,但是与之相连子株的叶片ABA含量并没有增加;并且气孔导度与ABA变化趋势一致.(1)草莓母株和子株间的水分运输是由二者的水势差驱动的;(2)ABA不会通过匍匐茎在母株和子株间传递并影响相邻子株气孔导度;(3)在水分异质性较大情况下,生理整合可明显提高克隆系统的碳同化能力和光系统Ⅱ激发能利用效率.     

Clonal integration affects growth and sediment properties of the first ramet generation,but not later ramet generations under severe light stress

克隆整合影响严重光胁迫下第一分株世代的生长和沉积物特征但不影响 后续分株世代的生长和沉积物特征 克隆整合通过缓冲环境压力和提高资源获取效率使克隆植物受益。然而,在一个克隆系统中,受益于克隆整合的连接分株世代的数量很少受到关注。我们进行了一个盆栽实验来评估沉水植物苦草 (Vallisneria natans)克隆系统内的生理整合程度,该克隆系统由一个母株和3个依次连接的后代分株组成。 母株生长在正常光照下,而后代分株被严重遮荫。母株与后代分株间的匍匐茎被切断或保持连接,但3个后代分株之间的连接仍然存在。与遮荫的后代分株连接时,苦草未遮荫的母株的光合能力显著增强,但其生物量积累大大减少。克隆整合显著增加了第一分株世代(相邻分株)的生物量积累和土壤的碳氮可用性、胞外酶活性和微生物生物量,但没有增加后续分株世代的这些特征。我们的结果表明,在严重光胁迫下,来自苦草母株的支持可能仅限于克隆系统中相邻的后代分株,这暗示着一个分株世代的效应。我们的结果有助于更好地理解克隆植物的层次结构和分段化。这些发现表明克隆整合程度在分株种群的生态相互作用中起着至关重要的作用。     

沙拐枣属植物同化枝和子叶的解剖学研究

采用石蜡切片技术,对相同生境下的戈壁沙拐枣、柴达木沙拐枣和英吉沙沙拐枣的子叶,及中国特有种柴达木沙拐枣、塔里木沙拐枣、阿拉善沙拐枣和英吉沙沙拐枣同化枝的横切面解剖结构进行观察研究.结果显示:(1)3种沙拐枣子叶均为全栅等面叶;表皮为单层细胞,上下表皮均分布气孔,栅栏组织以内为一圈连续排列的维管束鞘细胞;中脉和小叶脉排列近似M型,包埋于薄壁细胞中.(2)塔里木沙拐枣同化枝的保护组织、栅栏组织较发达,英吉沙沙拐枣同化枝机械组织和输导组织较为发达,阿拉善沙拐枣同化枝的栅栏组织较为发达,相比较柴达木沙拐枣同化枝的保护组织、机械组织和输导组织最不发达.(3)柴达木沙拐枣和英吉沙沙拐枣中子叶与同化枝的横切面各组织分布相似,主要差异为横切面形状、维管束排列方式和机械组织发达程度.研究表明,子叶与同化枝的解剖结构是该属植物在干旱环境下长期适应的结果,解剖结构的差异体现了种间、器官间对相同环境的不同适应策略.     

克隆整合对异质性盐分胁迫下积雪草生长的影响

以匍匐茎草本克隆植物积雪草(Centella asiatica)为材料进行盆栽试验,研究了克隆整合特性对异质性盐分胁迫条件下植物生长的影响。试验中将远端分株(较幼分株)分别处于盐分胁迫或正常土壤条件下,切断或保持其与近端分株(较老分株)间的匍匐茎连接。结果表明：盐分胁迫下,克隆整合提高了受胁迫远端分株和整个克隆片断的叶面积和生物量等生长指标;与未遭受盐分胁迫处理相比,匍匐茎连接处理导致远端分株的根冠比显著降低。克隆整合还减轻了盐分胁迫对分株的叶绿素含量和光化学效率的影响,但盐分胁迫下,匍匐茎连接处理远端分株的净光合速率与匍匐茎切断处理远端分株并无显著差异,连接受胁迫的远端分株并没有引起近端分株生物量的明显损耗以及光合速率的补偿性提高。总之,克隆整合促进了积雪草遭受盐分胁迫的分株和整个克隆片段的生长,这对于丰富和发展异质性环境胁迫下克隆植物的生态适应对策具有重要意义。     

火炬树雌雄母株克隆生长差异及其光合荧光日变化

火炬树(Rhus typhina Linn.)是兼有雌雄异株和克隆生长特性的外来木本植物。分别探讨火炬树雌雄母株克隆繁殖扩散能力的特点,分析其光合荧光反应的差异。采用CIRAS-2光合仪和FMS-2便携调制式荧光仪,并结合样圆调查法,比较火炬树雌雄母株的克隆分株数量和形态生长指标、光合生理参数的日变化特征,揭示火炬树雌雄异株的资源利用效率和对午间强光缓冲保护能力的雌雄差异。研究结果表明:1)火炬树雄性母株的克隆分株形态生长指标及数量均超过了雌性母株,且雄性母株形成克隆分株的年龄早于雌性母株1a;2)火炬树雄性母株的光能、水分和CO2利用效率和净光合速率均高于雌性母株,此结果为雄性母株克隆生长奠定了较为充足的营养基础;3)在晴天自然光的条件下,火炬树雄性母株未出现光抑制,而雌性母株出现了光抑制现象,非光化学猝灭系数(qN)日变化特征显示雌性母株的热耗散程度较高。因此,火炬树雄性母株的克隆生长力强于雌性母株。     

异质性重金属镉胁迫下克隆整合对匍匐茎草本植物积雪草生长的影响

 采用盆栽试验研究了异质性重金属镉胁迫下, 克隆整合对匍匐茎草本植物积雪草(Centella asiatica)生长的影响。将远端分株(相对年幼的分株)分别置于对照和镉胁迫处理下, 并对远端分株与近端分株(相对年长的分株)之间的匍匐茎进行切断或保持连接处理。研究结果显示: 镉胁迫处理显著降低了积雪草远端分株的净光合速率(P_n)、最大光量子产量(F_v/F_m)、叶绿素含量、叶面积、分株数和生物量; 克隆整合缓解了镉胁迫对远端分株生长的不利影响; 克隆整合不仅未导致相连近端分株的损耗, 而且相连近端分株的光合效率也没有表现出补偿性增加; 克隆整合降低了远端受胁迫分株的根冠比, 从而使之减少了对土壤中重金属镉的吸收; 匍匐茎切断和镉胁迫处理对近端分株、远端分株的叶柄长没有显著的影响。结果表明: 克隆整合提高了积雪草遭受镉胁迫的远端分株的生长, 改变了其生物量分配格局, 并有助于整个克隆片段在异质性重金属胁迫下的生长。该研究对于丰富和发展异质性环境胁迫下克隆整合的生态适应对策具有重要意义。     

风蚀和沙埋对塔克拉玛干沙漠南缘骆驼刺水分和光合作用的影响

塔克拉玛干沙漠南缘风沙活动十分频繁, 风蚀和沙埋是该地区自然植被生长发育的重要影响因子。该文以塔克拉玛干沙漠南缘策勒绿洲-沙漠过渡带为研究区, 以该区域主要建群种植物骆驼刺(Alhagi sparsifolia)为研究对象, 对一次强沙尘天气过后沙丘表面5种不同风蚀沙埋状况的骆驼刺植物进行标定(包括10 cm风蚀、5 cm风蚀、不蚀不积、10 cm沙埋、30 cm沙埋), 天晴后测定其叶水势、叶片含水量、光合参数和叶绿素荧光等参数, 分析研究自然环境条件下风蚀和沙埋对骆驼刺水分和光合作用的影响。结果表明: (1)风蚀显著降低了骆驼刺叶水势和叶片含水量, 进而导致植物气孔导度降低, 并引起植物光合速率和蒸腾速率的下降。风蚀的植物水分利用效率低于沙埋, 特别是在10 cm风蚀深度明显降低。 (2)沙埋增加了骆驼刺的叶水势、叶片含水量和气孔导度, 并引起植物光合速率和蒸腾速率的上升, 水分利用效率也得到提升。(3)风蚀条件下骆驼刺所受胁迫增加, 但可以通过增加活性反应中心的数量和光化学效率来抵消胁迫造成的不利影响。沙埋条件下骆驼刺受胁迫减轻, 反应中心吸收的光能和用于光化学反应的能量随着沙埋程度增加而减小, 这是骆驼刺适应风沙环境的一种生存策略。(4)与5 cm风蚀以及10 cm沙埋相比, 10 cm风蚀显著抑制骆驼刺的生长, 30 cm沙埋则会显著促进骆驼刺的生长。     

百里香无性系的克隆生长特征

植物克隆生长及其与生态适应性的关系是当今植物种群生态学研究的热点和前沿课题,但目前小半灌木克隆生长的研究开展不多。百里香(Thymus serpyllum var. asiaticus)是一种具有地面匍匐茎的草本状小半灌木,可在土壤侵蚀剧烈、基岩大面积裸露的砒砂岩区形成百里香单优群落,在维持生态系统稳定方面具有重要的生态学作用。皇甫川流域是砒砂岩大面积分布的典型区域,在这一地区对百里香无性系的克隆生长进行研究,不仅具有重要的学术价值,而且在生态环境建设方面也具有一定的现实意义。在皇甫川流域选择含三级分株的百里香无性系,对其各级分株的总生物量、各构件生物量及数量、各构件生物量占总生物量的百分比及其月变化进行了研究。结果表明: 1)母株与子代相比,在总生物量、构件生物量及数量上占有绝对优势,而且具有体型大、结构复杂的特点; 2)对生物量分配格局的研究显示,母株根的生物量在总生物量中所占的比例最大,其叶所占的比例较低。子代叶的生物量在总生物量中所占的比例最大,其根所占的比例较低;3)不同级别分株在生物量分配上的差异,揭示了相互连接的分株在功能上的差别,母株可能更侧重于养分和水分的吸收,子株则更侧重于光合生产;4)构件枝、茎、花生物量分配比月变化显示,子1代各构件的生长规律与母株的基本一致,子2代与母株和子1代的相比差异较大,分析认为这可能是分株间不同程度的生理整合作用造成的结果。     

Effects of the loss of clonal integration on four sedges that differ in ramet aggregation

Although clonal growth is a dominant mode of plant growth in wetlands, the importance of clonal integration, resource sharing among ramets, to individual ramet generations (mother and daughter) and entire clones of coexisting species has not been well investigated. This study evaluated the significance of clonal integration in four sedge species of varying ramet aggregations, from clump-forming species (Clumpers –Carex sterilis, Eleocharis rostellata), with tightly aggregated ramets (rhizomes<1cm), to runner species (Runners –Schoenoplectus acutus, Cladium mariscoides), with loosely aggregated ramets. We manipulated clonal integration by either severing connections between target mother and daughter ramets or leaving connections intact, and then planted them in an intact neighborhood of a fen in Michigan, USA. We measured growth parameters of original and newly produced ramets over two growing seasons and conducted a final biomass harvest, to address four hypotheses. First, we expected integrated clones to accumulate more biomass than severed clones. However, final clone-level biomass and ramet production were the same for both treatments in all species although severing initially stimulated ramet production by Schoenoplectus and produced a more compact ramet aggregation in Cladium. Second, we hypothesized that mother ramets would experience a cost of integration, through reduced ramet or biomass production, while daughters would experience a benefit, through increased resource availability from mothers. Mother ramets of Cladium suffered a cost from integration, while Schoenoplectus mothers suffered a slight cost and Carex daughters saw a slight benefit. Finally, we hypothesized that integration would be more active in runner species than in clumper species. Indeed, we documented more active integration in runners than clumpers, but none of the study species were dependent upon integration for growth or survival once daughter ramets were established with their own roots and shoots. This study demonstrates that integration between established ramets may not be the most important advantage to clonal growth in this wetland field site. The loss of integration elicited varied responses among coexisting species in their natural habitat, somewhat but not completely related to their growth form, suggesting that a combination of plant life history traits contributes to the dependence upon clonal integration among established ramets of clonal species.     

疏叶骆驼刺母株与子株间的水分整合

在未灌溉的土地上, 疏叶骆驼刺(Alhagi sparsifolia)通常不能进行有性繁殖, 克隆繁殖是其种群维持和延续的唯一方式。因此, 克隆性及其相关克隆性状(如水分整合)在疏叶骆驼刺自然种群的维持过程中可能扮演了极其重要的角色。该文通过疏叶骆驼刺母株和子株之间的间隔子切断和给母株补充水分的方法, 研究了母株和子株在各处理下的水势、叶形态和植株生长变化情况。结果表明: (1)间隔子切断后, 疏叶骆驼刺母株和子株正午水势均明显增大(p < 0.01), 说明间隔子切断使得母株和子株水分亏缺值都增大。(2)给母株补水后, 间隔子切断组和间隔子相连组中的母株水势均有明显增加, 同时间隔子相连组的子株水势明显增加(p < 0.01), 而间隔子切断组子株水势没有明显变化(p > 0.05)。(3)间隔子切断组的子株叶片含水率明显低于间隔子相连组子株, 而其株高、冠幅、分枝数和基径的增长量都明显小于间隔子相连组的子株(p < 0.01)。疏叶骆驼刺母株和子株间存在水分整合, 母株会通过根系向子株传输水分。研究成果对塔克拉玛干沙漠南缘的植被恢复以及水资源的合理利用有着重要的意义。     

Clonal integration enhances survival and performance of Potentilla anserina, suffering from partial sand burial on Ordos plateau, China

On Ordos plateau, a semi-arid, desertified area in China, sand burial is a common stress factor for plants. The extent to which sand burial occurs is heterogeneous and unpredictable in space and in time. Therefore, clonal fragments (i.e., interconnected ramets of a clonal plant) often experience partial sand burial, with some ramets buried in sand while the rest may remain unburied. It was hypothesized that clonal fragments are able to benefit from clonal integration, in case they experience partial sand burial. A pot experiment was conducted with Potentilla anserina, a stoloniferous herb often found on Ordos plateau. We used clonal fragments consisting of four interconnected ramets. In the experiment, the two proximal (older) ramets were unburied while the two distal (younger) ramets were either unburied (control) or buried with a 2, 4 or 6 cm deep layer of sand (burial treatments). The stolon connection between the proximal and the distal ramets was either severed or left intact. Stolon severing dramatically decreased the survival of buried ramets. Stolon severing and sand burial had significant effects on plant performance in terms of biomass production, number of leaves and leaf area. A cost–benefit analysis based on performance measures shows that the proximal ramets supported their connected distal ramets and did not incur any cost from this resource export. These results suggest that clonal integration, which is one of the functionally most important consequences of clonal growth, contributes significantly to our test species' capacity to withstand partial sand burial on Ordos plateau, a semi-arid and desertified area of China.     

Patterns of Solidago altissima ramet growth and mortality: the role of below-ground ramet connections

Summary For the rhizomatous perennial, Solidago altissima, I identified clonal fragments in the field, mapped ramet spatial locations, and documented patterns of ramet recruitment, growth, and mortality. Parent ramet size influenced the size and number of daughter ramets produced, and small ramets had lower survivorship and fecundity than large ramets. Similarly, small rhizomes tended to develop into small ramets, and ramets that survived to produce daughter ramets had longer parent-daughter rhizome connections than ramets that did not survive. In addition, most ramets that died during the growing season were connected to (genetically identical) ramets that persisted. There were large size inequalities among rhizomes, ramets, and clonal fragments. Inequalities in the size of ramets increased during the early part of the growing season, then decreased at the end of the season; similar patterns were observed for the growth of clonal fragments. In both instances, the decrease in size inequality could be attributed to the mortality of small individuals (ramets or clonal fragments). I found little evidence that ramet size hierarchies were structured by intraspecific competition. For example, path analyses and randomization tests indicated that size variation among S. altissima ramets was influenced little by the size of their near neighbors (but was influenced by parent size and rhizome size). In addition, within-season variation for the relative size and growth rate of individual ramets led to poor correlations between early and final ramet size; this result suggests that there was no stable hierarchy of dominant and suppressed ramets. I discuss implications of my results for contrasting interpretations of clonal plant population dynamics.     

CLONAL INTEGRATION: NUTRIENT SHARING BETWEEN SISTER RAMETS OF SOLIDAGO ALTISSIMA (COMPOSITAE)

To test whether sharing of resources occurs among connected ramets of the tall goldenrod, Solidago altissima, we examined the extent of clonal integration for nutrients. In a greenhouse experiment, two-ramet clones were grown in a triad of connected pots so that nutrients could be supplied to either sister ramet or to their old rhizome (mother rhizome). Mother rhizomes and their associated roots shared nutrients with daughter ramets; however, any nutrient sharing that occurred between sister ramets was too little to significantly affect their growth. In addition, sister ramets not only competed for nutrients through parental connections, but larger ramets inhibited the growth of smaller ramets. We suggest that, for tall goldenrod, a clonal growth strategy in which nutrients are not shared among sister ramets may increase genet fitness by reducing the rhizome production of ramets in poor-nutrient microsites. Consequently, the genet would produce relatively fewer ramets in unfertile areas and make better use of heterogeneous nutrient resources.     

Responses of Hedysarum Laeve , a guerrilla clonal semi-shrub in the Mu Us sandland, to local sand burial

In arid and semi-arid inland deserts, one of the environmental stresses for plants is recurrent sand burial, which can influence the physical and biotic microenvironments of the plants and soil. Previous studies have shown that different levels of sand burial have different effects on plants. Slight sand burial could increase the height increment, leaf biomass and the number of new ramets of the plants while heavy sand burial could impair the growth of the plants and even decrease their chances of survival. In other words, below a certain threshold level of burial, the growth of plants is stimulated probably because of multiple factors. However, as the level of burial increases, the positive response starts to decline until it becomes a negative value. Arid and semi-arid inland deserts are frequently colonized and stabilized by many rhizomatous clonal plants. Clonal physiological integration often helps clonal plants buffer local environmental stress encountered by ramets. A rhizomatous clonal semishrub, Hedysarum laeve (H. laeve), is the dominant plant species and important for vegetation restoration in the Mu Us sandland. To investigate whether clonal integration can increase the threshold of sand burial and help rhizomatous H. laeve tolerate heavy sand burial, we conducted a field experiment. The results showed that slight sand burial could accelerate ramet growth and enhance leaf biomass, stem biomass and shoot biomass, while heavy sand burial reducesed the biomass of the plant and impairs survival and growth of the ramets. Clonal integration increased the threshold of sand burial. Under heavy sand burial, ramets connected to other ramets not buried in sand were more in terms of height increment, stem biomass, leaf biomass and shoot biomass compared to the ramets encountering sand burial but disconnected from other ramets. It suggested that clonal physiological integration could help H. laeve ramets tolerate relatively heavy sand burial. We also discussed that clonal integration plays a role in H. laeve presence in the Mu Us sandland. __________ Translated from Journal of Plant Ecology (formerly Acta Phytoecologica Sinica), 2006, 30(2): 278–285 [译自: 植物生态学报]     

Clonal integration in Ranunculus reptans: by‐product or adaptation?

We studied fitness consequences of clonal integration in 27 genotypes of the stoloniferous herb Ranunculus reptans in a spatially heterogeneous light environment. We grew 216 pairs of connected ramets (eight per genotype) with mother ramets in light and daughter ramets in shade. In half of the pairs we severed the stolon connection between the two ramets at the beginning of the experiment. During the experiment, 52.7% of the ramet pairs with originally intact connection physically disintegrated. We detected significant variation among genotypes in this regard. Survival of planted ramets was 13.3% higher for originally connected pairs. Moreover, there was significant variation among genotypes in survival, in the difference in survival between plant parts developing from mother and daughter ramets, and in the effect of integration on this difference. In surviving plants connection between ramets decreased size differences between mother and daughter parts. Variation among genotypes was significant in growth and reproduction and marginally significant in the effect of physiological integration on growth and reproduction. Connected daughter ramets had longer leaves and internodes than daughters in severed pairs indicating that integration stimulated plant foraging in both the vertical and the horizontal plane. Observed effects of integration on fitness components in combination with genetic variation in maintenance and effects of connection indicate that clonal integration in R. reptans has the capability to evolve, and therefore suggest that clonal integration is adaptive. If genetic variation in integration is common, future studies on clonal integration should always use defined genetic material and many clones to allow extrapolation of results to population and wider levels.