光照强度和基质养分对匍匐茎草本金戴戴克隆生长和克隆形态的影响

在深度遮光(光照强度为高光条件的6.25%,约为自然光照的5.3%)或低养分条件下,金戴戴(Halerpestes ruthenica Ovcz.)生物量、初级分株叶面积、分株总数、匍匐茎总数和总长度均显著减小,而比节间长和比叶柄长显著增加.在低养分条件下,金戴戴匍匐茎平均节间长显著增加,而匍匐茎分枝强度和分株数显著减小.这些结果与克隆植物觅食模型相符合,表明当生长于异质性生境中,金戴戴可能通过以克隆生长和克隆形态的可塑性实现的觅养行为来增加对养分资源的摄取.在深度遮光条件下,金戴戴平均间隔子长度(即平均节间长和平均叶柄长)均显著减小.这一结果与以往实验中匍匐茎草本间隔子对中度和轻度遮光(光照强度为高光条件的13%～75%,>10%的自然光照)的反应不同.这表明,在深度遮光条件下匍匐茎克隆植物可能不发生通过间隔子可塑性实现的觅光行为.光照强度和基质养分条件的交互作用对许多性状如总生物量、匍匐茎总数和总长度、二级和三级分株数、分株总数、初级分株叶面积以及分枝强度均有十分显著的效应.在高光条件下,基质养分对这些性状有十分显著的影响;而在低光条件下,基质养分条件对这些性状不产生影响或影响较小.这表明,光照强度影响金戴戴对基质养分的可塑性反应.在深度遮光或低养分条件下,金戴戴可能通过减小匍匐茎节间粗度(增加比节间长)来增加或维持其相对长度,从而更有机会逃离资源丰度低的斑块.     

光照强度和基质养分对匍匐茎草本金戴戴克隆生长和克隆形态的影响

在深度遮光 (光照强度为高光条件的 6 .2 5% ,约为自然光照的 5.3% )或低养分条件下 ,金戴戴 (HalerpestesruthenicaOvcz.)生物量、初级分株叶面积、分株总数、匍匐茎总数和总长度均显著减小 ,而比节间长和比叶柄长显著增加。在低养分条件下 ,金戴戴匍匐茎平均节间长显著增加 ,而匍匐茎分枝强度和分株数显著减小。这些结果与克隆植物觅食模型相符合 ,表明当生长于异质性生境中 ,金戴戴可能通过以克隆生长和克隆形态的可塑性实现的觅养行为来增加对养分资源的摄取。在深度遮光条件下 ,金戴戴平均间隔子长度 (即平均节间长和平均叶柄长 )均显著减小。这一结果与以往实验中匍匐茎草本间隔子对中度和轻度遮光 (光照强度为高光条件的 1 3%～ 75% ,>1 0 %的自然光照 )的反应不同。这表明 ,在深度遮光条件下匍匐茎克隆植物可能不发生通过间隔子可塑性实现的觅光行为。光照强度和基质养分条件的交互作用对许多性状如总生物量、匍匐茎总数和总长度、二级和三级分株数、分株总数、初级分株叶面积以及分枝强度均有十分显著的效应。在高光条件下 ,基质养分对这些性状有十分显著的影响 ;而在低光条件下 ,基质养分条件对这些性状不产生影响或影响较小。这表明 ,光照强度影响金戴戴对基质养分的可塑性反应。在深度遮光     

匍匐茎草本植物形态可塑性、整合作用与觅食行为研究进展

综述了匍匐茎型克隆植物在形态可塑性、整合作用及觅食行为方面的研究进展。资源斑块性分布是生境异质性的特征之一,适应于异质性生境,匍匐茎植物对环境资源表现了一系列可塑性反应。本文着重从匍匐茎植物对光、水、肥的可塑性反应及其整合作用以及觅食行为等方面的研究进行总结分析,以期对匍匐茎型克隆植物进行更广泛深入的研究。     

Root Foraging Increases Performance of the Clonal Plant Potentilla reptans in Heterogeneous Nutrient Environments

Background

Plastic root-foraging responses have been widely recognized as an important strategy for plants to explore heterogeneously distributed resources. However, the benefits and costs of root foraging have received little attention.

Methodology/Principal Findings

In a greenhouse experiment, we grew pairs of connected ramets of 22 genotypes of the stoloniferous plant Potentilla reptans in paired pots, between which the contrast in nutrient availability was set as null, medium and high, but with the total nutrient amount kept the same. We calculated root-foraging intensity of each individual ramet pair as the difference in root mass between paired ramets divided by the total root mass. For each genotype, we then calculated root-foraging ability as the slope of the regression of root-foraging intensity against patch contrast. For all genotypes, root-foraging intensity increased with patch contrast and the total biomass and number of offspring ramets were lowest at high patch contrast. Among genotypes, root-foraging intensity was positively related to production of offspring ramets and biomass in the high patch-contrast treatment, which indicates an evolutionary benefit of root foraging in heterogeneous environments. However, we found no significant evidence that the ability of plastic foraging imposes costs under homogeneous conditions (i.e. when foraging is not needed).

Conclusions/Significance

Our results show that plants of P. reptans adjust their root-foraging intensity according to patch contrast. Moreover, the results show that the root foraging has an evolutionary advantage in heterogeneous environments, while costs of having the ability of plastic root foraging were absent or very small.     

匍匐茎草本蛇莓克隆构型对土壤水分的可塑性反应

克隆植物构型的可塑性有可能促进它对斑块性分布土壤水分资源的利用,因而可能具有生态学意义.在田间实验中,匍匐茎草本蛇莓(Duchesnea indica Focke)经历了不同土壤水分水平(土壤最大含水量的40%、60%、80%、100%等)处理,以研究土壤水分对蛇莓克隆构型的影响.结果表明:间隔子长度、分株密度、分枝角度和分枝强度呈二次曲线变化,土壤含水为最大含水量的80%的生境为最适.在不同土壤水分水平生境中,蛇莓克隆构型相关特征的可塑性变化可用动态Logistic模型进行模拟和预测,拟合效果较好.结合植物对环境异质性的利用对策,对所揭示的蛇莓克隆构型可塑性进行了讨论.     

匍匐茎草本蛇莓克隆构型对土壤水分的可塑性反应

克隆植物构型的可塑性有可能促进它对斑块性分布土壤水分资源的利用,因而可能具有生态学意义。在田间实验中,匍匐茎草本蛇莓（Duchesnea indica Focke)经历了不同土壤水分水平（土壤最大含水量的40%,60%,80%,100%等）处理,以研究土壤水分对蛇莓克隆构型的影响,结果表明：间隔子长度,分株密度,分枝角度和分枝强度呈二次曲线变化,土壤含水为最大含水量的80%的生境为最适,在不同土壤水分水平生境中,蛇莓克隆构型相关特征的可塑性变化可用动态Logistic模型进行模拟和预测,拟事效果较好,结合植物对环境异质性的利用对策,对所揭示的蛇莓克隆构型可塑性进行了讨论。     

Environmentally-induced functional specialization for locally abundant resources in the stoloniferous herb Duchesnea indica

Reciprocally patchy environments, where the availability of two resources are patchily distributed and negatively correlated in each patch, are common in many ecosystems. Interconnected ramets of clonal plants can specialize in the uptake of locally abundant resources. Ramet pairs of the stoloniferous herb Duchesnea indica were grown in reciprocally patchy environments i.e., one ramet of a pair was grown in the high light but low water patch (high light patch) and the other in the low light but high water patch (high water patch). Biomass allocation pattern (root-shoot ratio), morphological traits (leaf area and root length) and physiological traits (photosynthetic rate and chlorophyll content) were altered in a way that potentially enables ramets to enhance the capture of the locally abundant resource (i.e., increase the capture of light resource in the high light patch and of water in the high water patch). As a result,biomass and number of ramets in the connected ramet pairs were greatly improved. Functional specialization of ramets, modified by clonal integration, may have contributed greatly to the growth increase of D. indica in the reciprocally patchy environment.     

匍匐茎草本蛇莓克隆构型对土壤养分的可塑性反应

克隆植物构型的可塑性可使它在养分斑块性分布的环境中,相应地调整对土壤养分的获取对策,因而可能具有重要的生态学意义。在一项田间实验中,匍匐茎草本蛇莓(Duchesnea indica Focke）经历了不同土壤养分水平（高、中、低和对照）处理,以研究土壤养分对蛇莓克隆构型的影响。结果表明：随着土壤养分水平的增加,间隔子的长度和分枝角度均逐渐降低,而分枝强度和分株密度增加。在不同养分水平生镜中,蛇莓克隆构型相关特征的可塑性变化可用动态Logistic模型进行模拟和预测,拟合效果较好。结合植物对环境异质性的利用对策,对所揭示的蛇莓克隆构型可塑性进行了讨论。     

No evidence for nutrient foraging in root-sprouting clonal plants

Clonality is defined as vegetative reproduction via the production of ramets, which are, at least initially, connected by spacers. In general, there are three types of spacers of two origins. Whereas stolons are aboveground spacers, rhizomes are belowground spacers; however, both of stem origin. The third type of spacers are roots in root-sprouting plants. The possibility of foraging in clonal plants has attracted broad interest among ecologists but has been experimentally documented only for stoloniferous clonal plants foraging for light. Foraging for belowground resources has yet to be demonstrated, perhaps because tests of foraging have focused on clonal plants that spread laterally via stolons or rhizomes, i.e. stem organs. Lateral spread based on sprouting roots has not been considered even though, in addition to functioning as conduits between ramets, root spacers are able to sense and take up nutrients. We therefore hypothesized that root-sprouting clonal plants may be able to directly react to environmental heterogeneity and exhibit nutrient foraging. To test this hypothesis, we conducted two experiments with root-sprouters in nutrient-heterogeneous and -homogeneous environments. We found that plants produced more biomass when growing in a heterogeneous environment than in a homogeneous environment and that root biomass was greater in the nutrient-rich patches than in nutrient-poor patches. However, the number of ramets did not differ between patches in the heterogeneous environment. We conclude that plants whose clonality is based on roots, similarly as plants whose clonality is based on stolons or rhizomes, do not exhibit accumulation of ramets in nutrient-rich patches. Foraging at the organ level, i.e. by roots, seems to be more probable in this clonal group. To analyse how clonal plants with different clonal strategies perceive and react to environmental heterogeneity, researchers must account for the high variability in clonal growth forms and in scales of environmental heterogeneity.     

Environmentally-induced functional specialization for locally abundant resources in the stoloniferous herb Duchesnea indica

Reciprocally patchy environments, where the availability of two resources are patchily distributed and negatively correlated in each patch, are common in many ecosystems. Interconnected ramets of clonal plants can specialize in the uptake of locally abundant resources. Ramet pairs of the stoloniferous herb Duchesnea indica were grown in reciprocally patchy environments i.e., one ramet of a pair was grown in the high light but low water patch (high light patch) and the other in the low light but high water patch (high water patch). Biomass allocation pattern (root-shoot ratio), morphological traits (leaf area and root length) and physiological traits (photosynthetic rate and chlorophyll content) were altered in a way that potentially enables ramets to enhance the capture of the locally abundant resource (i.e., increase the capture of light resource in the high light patch and of water in the high water patch). As a result,biomass and number of ramets in the connected ramet pairs were greatly improved. Functional specialization of ramets, modified by clonal integration, may have contributed greatly to the growth increase of D. indica in the reciprocally patchy environment.     

Adaptive plasticity in response to light and nutrient availability in the clonal plant Duchesnea indica

克隆植物蛇莓对光照强度和养分条件的适应性可塑性 表型可塑性可帮助植物缓冲环境压力并使其表型与当地环境相匹配,但目前仅少数性状的可塑性被广泛认为是适应性的。为充分理解可塑性的适应性意义,仍需进一步研究更多的植物功能性状及其环境因子。本研究将匍匐茎克隆植物蛇莓(Duchesnea indica)的21个基因型种植于不同的光照和养分条件下,并利用选择梯度分析检测了形态和生理可塑性对光照强度和养分有效性变化的适应性值。在遮荫条件下,蛇莓适合度(果实数、分株数和生物量)降低,节间缩短变细,成熟叶叶绿素含量降低,但叶柄长度、比叶面积、老叶叶绿素含量均增加。在低养分条件下,植株叶柄缩短,叶面积缩小变厚,叶绿素含量降低,但果实数量和根冠比增加。选择梯度分析表明,叶柄长度和老叶叶绿素含量对光照变化的可塑性是适应性的,老叶和成熟叶叶绿素含量对养分变化的可塑性也是适应性的。因此,不同性状的可塑性适应值取决于特定的生态背景。该研究的发现有助于理解克隆植物表型可塑性响应环境变化的适应性意义。     

根茎型植物扁秆荆三棱对光照强度和养分水平的生长响应及资源分配策略

自然界中光照和养分因子常存在时空变化,对植物造成选择压力。克隆植物可通过克隆生长和生物量分配的可塑性来适应环境变化。尽管一些研究关注了克隆植物对光照和养分因子的生长响应,但尚未深入全面了解克隆植物对光照和养分资源投资的分配策略。以根茎型草本克隆植物扁秆荆三棱(Bolboschoenus planiculmis)为研究对象,在温室实验中,将其独立分株种植于由2种光照强度(光照和遮阴)和4种养分水平(对照、低养分、中养分和高养分)交叉组成的8种处理组合中,研究了光照和养分对其生长繁殖及资源贮存策略的影响。结果表明,扁秆荆三棱的生长、无性繁殖及资源贮存性状均受到光照强度的显著影响,在遮阴条件下各生长繁殖性状指标被抑制。且构件的数目、长度等特征对养分差异的可塑性响应先于其生物量积累特征。在光照条件下,高养分处理的总生物量、叶片数、总根茎分株数、长根茎分株数、总根茎长、芽长度、芽数量等指标大于其他养分处理,而在遮阴条件下,其在不同养分处理间无显著差异,表明光照条件可影响养分对扁秆荆三棱可塑性的作用,且高营养水平不能补偿由于光照不足而导致的生长能力下降。光照强度显著影响了总根茎、总球茎及大、中、小球茎的生物量分配,遮阴条件下,总生物量减少了对地下部分根茎和球茎的分配,并将有限的生物量优先分配给小球茎。总根茎的生物量分配未对养分发生可塑性反应,而随着养分增加,总球茎分配下降,说明在养分受限的环境中球茎的贮存功能可缓冲资源缺乏对植物生长的影响。在相同条件下,根茎生物量对长根茎的分配显著大于短根茎,以保持较高的繁殖能力;而总球茎对有分株球茎的生物量分配小于无分株球茎,表明扁秆荆三棱总球茎对贮存功能的分配优先于繁殖功能。研究为进一步理解根茎型克隆植物对光强及基质养分环境变化的生态适应提供了依据。     

Evolutionary and organismic constraints on the relationship between spacer length and environmental conditions in clonal plants

The rate of lateral spread of clonal plants is considered a plastic trait that responds directly to environmental conditions. However, this response is likely constrained by evolutionary history and other species attributes. Here we ask how the relationships between lateral spread and the distribution of herbaceous plant species in different environments are influenced by the type of spacer (epigeogenous versus hypogeogenous rhizome), its persistence (integrator versus splitter), and the height and phylogeny of the plant. Analysis of spacer length of 367 species from temperate to arctic Europe revealed that other plant characteristics modulate the relationship between spacer length and environmental conditions. While plants with epigeogenous rhizomes, which have usually shorter spacers than hypogeogenous rhizomes, were associated with illuminated habitats, plants with hypogeogenous rhizomes were associated with warm habitats. These relationships were also shown within the specific rhizome type, as within the group of species with epigeogenous rhizomes, those having short spacers were associated with more light. The trend toward long spacers in warm environment was detected within both epigeogenous and hypogeogenous rhizome bearing species. Splitters were found to be associated with wet, nutrient rich habitats irrespective of rhizome type. When plant height was accounted for by using the ratio of spacer length to plant height (L:H) instead of absolute spacer length, no relationship with environmental variables was found until phylogenetic relationships among the species were taken into account. This implies that overall variability in L:H ratio in the dataset masked trends common for different taxonomic groups. Future comparative studies relating particular clonal growth forms or individual traits to environmental conditions should consider the constraints arising from other growth characteristics and evolutionary history of the subject species.     

Clonal plasticity in response to nutrient availability in the pseudoannual herb,Trientalis europaea L.

Trientalis europaea plants were subjected to four levels of nutrient availability to test two hypotheses: (1) Clonal morphology of pseudoannuals with short-lived rhizomes is responsive to nutrient availability in terms of spacer length (a negative correlation expected) and branching intensity (a positive correlation expected), and (2) the size of the hibernacles of T. europaea shows a positive correlation with nutrient availability. The results support the first hypothesis, since the primary spacers of T. europaea were longer at lower nutrient levels while the branching intensity of the primary rhizomes increased at increasing nutrient supply. The second hypothesis was not confirmed, however; the plants produced fewer, but bigger hibernacles at lower levels of nutrient availability. The ecological significance of the results is discussed in the context of foraging for essential resources and habitat-related effects of hibernacle size on survival and establishment chances of daughter ramets.     

Invasive clonal plant species have a greater root-foraging plasticity than non-invasive ones

Clonality is frequently positively correlated with plant invasiveness, but which aspects of clonality make some clonal species more invasive than others is not known. Due to their spreading growth form, clonal plants are likely to experience spatial heterogeneity in nutrient availability. Plasticity in allocation of biomass to clonal growth organs and roots may allow these plants to forage for high-nutrient patches. We investigated whether this foraging response is stronger in species that have become invasive than in species that have not. We used six confamilial pairs of native European clonal plant species differing in invasion success in the USA. We grew all species in large pots under homogeneous or heterogeneous nutrient conditions in a greenhouse, and compared their nutrient-foraging response and performance. Neither invasive nor non-invasive species showed significant foraging responses to heterogeneity in clonal growth organ biomass or in aboveground biomass of clonal offspring. Invasive species had, however, a greater positive foraging response in terms of root and belowground biomass than non-invasive species. Invasive species also produced more total biomass. Our results suggest that the ability for strong root foraging is among the characteristics promoting invasiveness in clonal plants.     

匍匐茎草本蛇莓对基质养分条件的克隆可塑性

A pot experiment with three levels of nutrient (N, P, K) supply was carried out to investigate clonal plasticity of stoloniferous herb Duchesnea indica Focke in response to nutrient availability. The plants had greater biomass at higher levels of nutrient availability. The root/shoot ratio of the plants changed with the nutrient availability in the following order: low level > high level > medium level. They had the largest biomass allocation to stolon at the medium level of nutrient availability. The biomass allocation to petiole did not respond to the treatments. The plants formed more stolons and ramets at the high and medium levels than the low level of nutrient availability. The petiole length, specific petiole weight（mg/cm）and stolon internode length of the plants did not respond to the treatments, while the specific stolon weight (mg/cm）of the plants was greater at the high and medium levels than the low level of nutrient availability. The results have been discussed in the context of adaptation of clonal plants to environmental heterogeneity.     

Effects of Spatial Scale of Soil Heterogeneity on the Growth of a Clonal Plant Producing Both Spreading and Clumping Ramets

Soil nutrients are commonly heterogeneously distributed at different spatial scales. Although numerous studies have tested the effects of soil nutrient heterogeneity on growth of clonal plants producing either spreading ramets or clumping ramets, no study has examined the effects on the growth of clonal plants producing both spreading and clumping ramets and how spatial scale affects such effects. To test these effects, clones of Buchloe dactyloides, a stoloniferous clonal plant that produces both clumping and spreading ramets, were grown in six heterogeneous environments with different patch sizes and one homogeneous environment containing the same quantity of nutrients. Total biomass, total number of ramets, number of clumping ramets, number of spreading ramets, spacer length, or root:shoot ratio of the whole plants did not differ significantly among the seven treatments. However, at the patch level there were significant effects of patch size by nutrient level on biomass, number of ramets, number of spreading ramets, and number of clumping ramets, and these four variables were significantly larger in the nutrient-rich patches than in the nutrient-poor patches in the heterogeneous treatment with the largest patch size, but not in the other five heterogeneous treatments with smaller patch sizes. Neither nutrient level nor patch size significantly affected spacer length or root:shoot ratio. Based on our results, we propose that B. dactyloides can efficiently exploit nutrient-rich patches by a plastic response of clumping ramets and spreading ramets at larger spatial scales of soil heterogeneity but not at smaller ones.     

Plasticity in R/S ratio, morphology and fitness-related traits in response to reciprocal patchiness of light and nutrients in the stoloniferous herb, Glechoma longituba L

Clonal fragments of the stoloniferous herb Glechoma longituba were subjected to a complementary patchiness of light and soil nutrients including two spatially homogeneous treatments (SR–SR and IP–IP) and two spatially heterogeneous treatments (IP–SR and SR–IP). SR and IP indicate patches (shaded, rich) with low light intensity (shaded, S), high nutrient availability (rich, R) and patches (illuminated, poor) with high light intensity (illuminated, I) and low nutrient availability (poor, P), respectively. Plasticity of the species in root–shoot ratio, fitness-related traits (biomass, number of ramets and dry weight per ramet) and clonal morphological traits (length and specific length of stolon internodes, area and specific area of laminae, length and specific length of petioles) were experimentally examined. The aim is to understand adaptation of G. longituba to the environment with reciprocal patches of light and soil nutrients by plasticities both in root–shoot ratio and in (clonal) morphology. Our experiment revealed performance of the clonal fragments growing from patches with high light intensity and low soil nutrient availability into the adjacent opposite patches was increased in terms of the fitness-related characters. R/S ratio and clonal morphology were plastic. Meanwhile, the capture of light resource from the light-rich patches was enhanced while the capture of soil nutrients from either the nutrient-rich or the nutrient-poor patches was not. Analysis of cost and benefit disclosed positive effects of clonal integration on biomass production of ramets in the patches with low light intensity and high soil nutrient availability. These results suggest an existence of reciprocal translocation of assimilates and nutrients between the interconnected ramets. The reinforced performance of the clonal fragments seems to be related with specialization of clonal morphology in the species.     

Complex trait relationships between leaves and absorptive roots: Coordination in tissue N concentration but divergence in morphology

Leaves and absorptive roots (i.e., first‐order root) are above‐ and belowground plant organs related to resource acquisition; however, it is controversy over whether these two sets of functional traits vary in a coordinated manner. Here, we examined the relationships between analogous above‐ and belowground traits, including chemical (tissue C and N concentrations) and morphological traits (thickness and diameter, specific leaf area and root length, and tissue density) of 154 species sampling from eight subtropical and temperate forests. Our results showed that N concentrations of leaves and absorptive roots were positively correlated independent of phylogeny and plant growth forms, whereas morphological traits between above‐ and belowground organs varied independently. These results indicate that, different from plant economics spectrum theory, there is a complex integration of diverse adaptive strategies of plant species to above‐ and belowground environments, with convergent adaptation in nutrient traits but divergence in morphological traits across plant organs. Our results offer a new perspective for understanding the resource capture strategies of plants in adaptation to heterogeneous environments, and stress the importance of phylogenetic consideration in the discussion of cross‐species trait relationships.     

Clonal Plasticity in Response to Reciprocal Patchiness of Light and Nutrients in the Stoloniferous Herb Glechoma longituba L.

Interconnected ramets of clonal plants can functionally specialize in the uptake of resources from aboveground and/or underground sources. Ramet pairs of the clonal stoloniferous herb Glechoma Iongltuba L. were grown In spatially heterogeneous environments with complementary availability of light and nutrients. Plasticity with respect to root-shoot ratio, fitness-related traits （biomass, number of ramets and dry weight per ramet）, morphological traits （lamina area, root length） were experimentally examined. The aim was to understand the adaptation of G. Iongltuba to an environment with reciprocal patchiness of light and soil nutrients by plasticity In Its root-shoot ratio and clonal morphology. The results showed that the performance of ramets growing In patches with high light Intensity and low soil nutrients into the adjacent opposite patches was Increased in terms of fitness-related traits. However, the performance of those from patches with low light Intensity and high soil nutrients into the adjacent opposite patches was not changed. The root-shoot ratio and clonal morphology were plastic. Morphological traits such as lamina area and root length were altered In a way that enhanced the capture of light resources and soil nutrients. Apparent reciprocal resource transport between the ramets In an environment of reciprocal patchiness of resources can enhance the growth of ramets with complementary resource deficiencies.