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1.
Physiological integration and foraging behavior have both been proposed as advantages for clonal growth in heterogeneous environments. We tested three predictions concerning their short- and long-term effects on the growth of the clonal perennial sedge Schoenoplectus pungens (Pers.) Volk. ex Schinz and R. Keller: (1) growth would be greatest for clones with connected rhizomes and on heterogeneous soil, (2) clones would preferentially place biomass in the nutrient-rich patches of a spatially heterogeneous environment, and (3) physiological integration would decrease a clone’s ability to forage. We tested our predictions by growing S. pungens clones for 2 years in an experimental garden with two severing treatments (connected and severed rhizomes) crossed with two soil treatments (homogeneous and heterogeneous nutrient distribution). Severing treatments were only carried out in the first year. As predicted, severing significantly decreased total biomass and per capita growth rate in year one and individual ramet biomass both in year one and the year after severing stopped. This reduction in growth was most likely caused by severing damage, because the total biomass and growth rate in severed treatments did not vary with soil heterogeneity. Contrary to our prediction, total biomass and number of ramets were highest on homogeneous soil at the end of year two, regardless of severing treatment, possibly because ramets in heterogeneous treatments were initially planted in a nutrient-poor patch. Finally, as predicted, S. pungens concentrated ramets in the nutrient-rich patches of the heterogeneous soil treatment. This foraging behavior seemed enhanced by physiological integration in the first year, but any possible enhancement disappeared the year after severing stopped. It seems that over time, individual ramets become independent, and parent ramets respond independently to the conditions of their local microsite when producing offspring, a life-history pattern that may be the rule for clonal species with the spreading “guerrilla” growth form.  相似文献   

2.
Previous lines of investigation assuming potential advantage of clonal integration generally have neglected its plasticity in complex heterogeneous environments. Clonal plants adaptively respond to abiotic heterogeneity (patchy resource distribution) and herbivory‐induced heterogeneity (within‐clone heterogeneity in ramet performance), but to date little is known about how resource heterogeneity and simulated herbivory jointly affect the overall performance of clones. Partial damage within a clone caused by herbivory might create herbivory‐induced heterogeneity in a resource‐homogeneous environment, and might also decrease or increase the extent of heterogeneity under resource‐heterogeneous conditions. We conducted a greenhouse experiment in which target‐ramets of Leymus chinensis segments within homogeneous or heterogeneous nutrient treatments were subject to clipping (0% or 75% shoot removal). In homogeneous environments with high (9:9) nutrient availability, ramet biomass of L. chinensis with intact or severed rhizomes is 0.70 or 0.69 g. Conversely, target‐ramet biomass with intact rhizomes is obviously lower than that of the severed target‐ramets in the homogeneous environments with medium (5:5) and low (1:1) nutrient availability. High resource availability and the presence of herbivory can alleviate negative effects of rhizome connection under homogeneous conditions, by providing copious resource or creating herbivory‐induced heterogeneity respectively. Herbivory tolerance of clonal fragments with connected rhizomes was higher than that of fragments with severed rhizomes under heterogeneous conditions. These findings confirmed the unconditional advantage of clonal integration on reproduction under the combined influence of resource heterogeneity and simulated herbivory. Moreover, our results made clear the synergistically interactive effects of resource heterogeneity and simulated herbivory on costs and benefits of clonal integration. This will undoubtedly advance our understanding on the plasticity of clonal integration under complex environmental conditions.  相似文献   

3.
Pauliukonis  Nijole  Gough  Laura 《Plant Ecology》2004,173(1):1-15
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.  相似文献   

4.
Ming Dong  Bao Alaten 《Plant Ecology》1999,141(1-2):53-58
In a field experiment, Psammochloa villosa plants were subjected to rhizome severing. Severing rhizomes reduced growth in the young, detached rhizome segments compared to the controls in terms of all measured clonal growth-related characters, i.e. number of rhizomes and shoots, total rhizome length and total number of rhizome nodes. In a container experiment, the control ramets received uniform water and nutrient supply but in heterogeneous treatments high and low levels of water and nutrient supply, respectively were established. The number of ramets, total rhizome length, dry weight per ramet and biomass allocation to the rhizome had higher values at high water and nutrient supply, while spacer length (length of rhizome between shoots) and rhizome internode length were not affected. The local response of ramets given low water supply was enhanced due to connection to a well watered parent ramet in terms of number of ramets, total rhizome length and dry weight per ramet. A remote effect was not observed in the other treatments or in the other measured characters.  相似文献   

5.
We studied water trnaslocation between interconnected mother and daughter ramets in two rhizomatous Carex species, using a newly developed quantitative method based on deuterium tracing. Under homogeneous conditions, in which both ramets were subjected either to wet or dry soil, little water was exchanged between the ramets. When the ramet pair was exposed to a heterogeneous water supply, water translocation became unidirectional and strongly increased to a level at which 30–60% of the water acquired by the wet ramet was exported towards the dry ramet. The quantity of water translocated was unrelated to the difference in water potential between the ramets, but highly correlated to the difference in leaf area. In both species, the transpiration of the entire plant was similar under heterogeneous and homogeneous wet conditions. This was a direct result of an increase in water uptake by the wet ramet in response to the dry conditions experienced by the interconnected ramet. In C. hirta, the costs and benefits of integration in terms of ramet biomass paralleled the responses of water consumption. This species achieved a similar whole-plant biomass in heterogeneous and homogeneous wet treatments, and water translocation was equally effective in the acropetal and basipetal directions. In C. flacca, responses of biomass and water consumption did not match and, under some conditions, water translocation imposed costs rather than benefits to the plants of this species. It is concluded that enhanced resource acquisition by donor ramets may be of critical importance for the net benefits of physiological integration in clonal plants.  相似文献   

6.
Preformation of organs involves the initiation of vegetative and generative tissues at least one season before they are actually produced. It is a strategy to deal with environments characterized by predictable seasonality as it enables fast growth of plants at the onset of favorable conditions. However, early preformation also strongly restricts plants in their response to unpredictable environmental changes and disturbance. In this study we investigated the response of the clonal forest understory herb Uvularia perfoliata to disturbance and resource limitation. In U. perfoliata shoot characteristics, as well as vegetative and sexual reproduction are determined at the end of the previous growing season. Plants were grown under two light levels and the rhizome connection between parent and offspring ramets were severed at various times during the growing period. Disturbance did not affect total biomass accumulation but it did affect the relative allocation and survival probability of parents and offspring ramets. Early severing resulted in increased survival chance and future fitness of the parent ramet, while late severing resulted in a higher survival chance and increased fitness of offspring ramets. The response was mediated by plant size and resource availability. These results show that the life history of U. perfoliata includes the possibility to alleviate the effects of disturbance even though the species is characterized by strong developmental canalization through organ preformation.Co-ordinating editor: J. Tuomi  相似文献   

7.
This study examined the benefits associated with resource sharing among interconnected ramets spanning a soil salinity gradient. Clones of Hydrocotyle bonariensis, a rhizomatous dune perennial, expand into salt marsh communities from surrounding upland dune systems in coastal North Carolina. In rhizome-severing experiments conducted under both field and laboratory conditions, Hydrocotyle was shown to proliferate ramets under saline conditions, provided that these ramets were connected to other ramets growing in nonsaline conditions. Ramets that benefited from resource integration did not appear to be affected by local salt exposure in that these ramets were morphologically similar to those grown under nonsaline conditions. Supporting ramets incurred no net cost in terms of biomass or ramet production, but there was an increased percent allocation to roots and rhizomes. Ramets grown in saline conditions without the benefit of clonal integration showed high mortality and produced little or no net clonal growth. It is likely that the acropetal movement of water allowed Hydrocotyle clones to ameliorate the heterogeneous saline conditions associated with coastal environments.  相似文献   

8.
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。  相似文献   

9.
《植物生态学报》2013,37(8):699
动物对植物的采食会刺激植物进行补偿性更新生长, 克隆整合效应能够通过分株之间的物质传输增强克隆植物的这种补偿生长。现今对克隆整合效应在箭竹(Fargesia)补偿更新中的作用仍未得到全面认识。2011年10月到2012年11月, 设立了糙花箭竹(Fargesia scabrida)和缺苞箭竹(F. denudata)各40个样方, 分别进行不剪除样方内分株和剪除样方内分株数量的25%、50%、75%四种模拟采食干扰处理, 并将样方四周的根状茎切断或保持连接。从2012年6月起观测并统计了箭竹分株种群的累积出笋率、总出笋率、补充率, 以及新生分株的株高、基径和单株生物量。结果表明: (1)在不剪除分株的样方, 切断根状茎连接显著增加了糙花箭竹的出笋率和补充率, 但降低了新生分株的株高和单株生物量, 也显著降低了缺苞箭竹的出笋率和补充率; (2)保持根状茎连接时, 25%的剪除强度仅仅降低了糙花箭竹新生分株的单株生物量; 同样在保持根状茎连接的条件下, 25%、50%的剪除强度使缺苞箭竹种群的补充率有所降低, 而切断根状茎后缺苞箭竹在25%的剪除强度下的分株补充率反而升高; (3) 75%的剪除强度并未影响两种箭竹新生分株数量更新, 但造成新生分株质量显著下降; 切断根状茎连接显著降低了糙花箭竹的新生分株的株高和基径, 对缺苞箭竹影响不显著。实验证明克隆整合影响了两种箭竹新生分株的萌发、存活和生长, 但不是两种箭竹进行补偿更新的主要机制, 仅在糙花箭竹分株种群受到重度采食干扰后的更新中才起到明显的促进作用; 两种箭竹均能在50%的剪除强度下通过补偿生长恢复种群的稳定, 75%的剪除强度则会造成箭竹新生分株质量的下降。  相似文献   

10.
Sui Y  He W  Pan X  Dong M 《Annals of botany》2011,107(4):693-697

Background and Aims

Mechanical stimulation (MS) often induces plants to undergo thigmomorphogenesis and to synthesize an array of signalling substances. In clonal plants, connected ramets often share resources and hormones. However, little is known about whether and how clonal integration influences the ability of clonal plants to withstand MS. We hypothesized that the effects of MS may be modulated by clonal integration.

Methods

We conducted an experiment in which ramet pairs of Leymus secalinus were subjected to three treatments: (1) connected ramet pairs under a homogeneous condition [i.e. the proximal (relatively old) and distal (relatively young) ramets were not mechanically stressed]; (2) connected ramet pairs under a heterogeneous condition (i.e. the proximal ramet was mechanically stressed but the distal ramet was not); and (3) disconnected ramet pairs under the same condition as in treatment 2. At the end of the experiment, we harvested all plants and determined their biomass and allocation.

Key Results

Clonal integration had no significant influence on measured traits of distal L. secalinus ramets without MS. However, under MS, plants with distal ramets that were connected to a mother ramet produced more total plant biomass, below-ground biomass, ramets and total rhizome length than those that were not connected. Partial MS exerted local effects on stimulated ramets and remote effects on connected unstimulated ramets. Partial MS increased total biomass, root/shoot ratio, number of ramets and total rhizome length of stimulated proximal ramets, and increased total biomass, root weight ratio, number of ramets and total rhizome length of connected unstimulated ramets due to clonal integration.

Conclusions

These findings suggest that thigmomorphogenesis may protect plants from the stresses caused by high winds or trampling and that thigmomorphogenesis can be strongly modulated by the degree of clonal integration.  相似文献   

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