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Table of Content
    Volume 31 Issue 4
    30 July 2007
    SHEN Dong-Wei, LI Yuan-Yuan, CHEN Xiao-Yong
    Chin J Plant Ecol. 2007, 31 (4):  552-560.  doi:10.17521/cjpe.2007.0071
    Abstract ( 2776 )   Full Text ( 6 )   PDF (303KB) ( 1301 )   Save
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    Clonal reproduction produces genetically identical ramets. Generally, local clonal diversity is determined by the dynamic balance between loss of established genets and recruitment of new genotypes via sexual reproduction or colonization, as described by Eriksson's recruitment mechanism. However, environmental factors also play important roles in clonal diversity. For example, disturbance will affect local clonal diversity by increased recruitment and mortality of seedlings. Genetic variation is a prerequisite for evolutionary adaptation to environmental changes and plays a key role in the survival of a population or a species. However, recent studies indicate that genotypic diversity also has instantaneous effects. High genotypic diversity might enhance population stability due to high probability of presence of resistant genotypes and/or biological insurance. Recent studies showed that clonal diversity may increase primary production, maintain faunal richness and/or abundance, and affect biogeochemical processes, as does species diversity. Mechanisms of clonal diversity effects on ecosystem functioning are discussed.

    LU Jian-Ying, MA Rui-Jun, SUN Kun
    Chin J Plant Ecol. 2007, 31 (4):  561-567.  doi:10.17521/cjpe.2007.0072
    Abstract ( 2778 )   Full Text ( 10 )   PDF (316KB) ( 1469 )   Save
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    Aims Polygonum viviparum, which is widely distributed in eastern Qinghai-Tibet Plateau in China, is a clonal plant species with two modes of reproduction, clonal propagation by below-ground rhizomes and bulbils and sexual by seeds. This study investigated clonal structure and diversity (monoclonal or multiclonal population) and the relationship between clonal diversity and the altitude. Our objective was to examine the adaptive strategy of alpine plants to varied environments and establish a foundation for understanding reproduction and distribution of clonal plants.
    Methods We selected seven populations in eastern Qinghai-Tibet Plateau along an altitudinal gradient and sampled 20 individuals in each population with at least 1 m between individuals to avoid individuals from the same clone. We employed random amplified polymorphic DNA (RAPD) technology for studying clonal structure and diversity and analyzed the relationship between clonal diversity and altitude by SPSS software.
    Important findings We selected 13 random primers for amplification and found 117 repetitive loci with 84 polymorphic loci (total average percentage of polymorphic loci was 71.79%). We differentiated 43 RAPD genotypes among the 140 plants sampled. Mean Simpson's index was 0.639, and mean PD was 0.307, slightly higher than the mean of Ellstrand (PD=0.17, D=0.62). There was a clear mosaic among P. viviparum clones, probably because of diverse clonal structure. The formations of P. viviparum populations included guerilla, phalanx and a transitional type. Clonal diversity was independent of altitude.

    XIANG Wu-Sheng, LI Xian-Kun, SU Zong-Ming, OU Zu-Lan, LU Shu-Hua
    Chin J Plant Ecol. 2007, 31 (4):  568-575.  doi:10.17521/cjpe.2007.0073
    Abstract ( 2528 )   Full Text ( 3 )   PDF (323KB) ( 1274 )   Save
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    Aims Taxus chinensis var. mairei is the material from which taxol, an effective low-toxicity cancer-resistance medicine, is distilled. This species reproduces asexually, especially through sprouting from stems, which enables Taxus to expand its spatial occupation and maintain its population. Therefore, study on clonal properties of Taxus populations may provide a scientific basis for protecting and regenerating populations. This study addresses the following questions: 1) what are the fractal properties of population distribution patterns, 2) are clonal architecture and fractal properties correlated and 3) are fractal properties and aggregation correlated?
    Methods Based on a survey of Taxus, we established four 40 m × 15 m plots in its central distribution area in Yuanbaoshan Nature Reserve. For each plot, we determined the spatial coordinates of each Taxus individual. For Taxus > 3 m tall, we measured height, crown size, height to branches and diameter at breast height; for shorter Taxus seedlings and saplings, only height was measured. We also estimated or measured cover and height of shrubs and herbs. Fractal properties of population patterns were analyzed by using the box-counting dimension and the information dimension.
    Important findings The box-counting dimension ranged from 0.993 1 to 1.353 1, which was far from the theoretical value 2, indicating low degree of spatial occupation. Significant correlation between the clonal architecture index and the box-counting dimension indicates that degree of spatial occupation was closely related to clonal architecture, i.e., populations tending to have phalanx clonal architecture had a stronger degree of spatial occupation than those tending to have guerrilla clonal architecture. The information dimension varied from 1.350 8 to 1.652 1 with community type. The Pearson correlation between information dimension and pattern index is significant, suggesting that differences of information dimension could reflect variation of the aggregation intensity. Information dimension was closely related to number and spatial distribution patterns of ramets.

    WANG Qiong, LIAO Yong-Mei
    Chin J Plant Ecol. 2007, 31 (4):  576-587.  doi:10.17521/cjpe.2007.0074
    Abstract ( 2842 )   Full Text ( 5 )   PDF (571KB) ( 1268 )   Save
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    Aims In natural environments, resources of critical importance to plant growth are patchily distributed, even at a small spatial scale. The aims of this study are to address: 1) Centella asiatica exploitation of heterogeneous microsites in different habitats, 2) hierarchical effects of habitats and microsites with different herbaceous coverage on growth traits of C. asiatica, and 3) differences in hierarchical response patterns for large and small scales of heterogeneous habitats.
    Methods Microsites with low and high herbaceous coverage were selected in abandoned grassland slope and forest edge habitats. We measured morphological and physiological characteristics of C. asiatica in spring 2004 and 2005 at three levels: ramet population, clonal fragment and leaf. Environmental factors of different microsites were investigated again in September 2006.
    Important findings At the ramet population level, we observed no effect of habitat (forest edge vs. abandoned grassland slope). Root-shoot ratio of ramet population with low herbaceous coverage was significantly higher than that with high herbaceous coverage. At the level of clonal fragment, root dry weight, flower and fruit dry weight were significantly higher and internode length of primary and total stolons were shorter on abandoned grassland slope. Root-shoot ratio and number of primary stolons were significantly larger with low herbaceous coverage, but flower and fruit dry weight, internode length of secondary stolon and internode length of total stolon were lower. At the leaf level, lamina length, lamina width and lamina area were larger on abandoned grassland slope and with high herbaceous coverage. Plants with high herbaceous coverage had larger petiole length and specific petiole length. No significant effects of habitat and microsite on chlorophyll content were observed. These findings indicated that there were hierarchical effects of habitat and microsite on the growth traits of C. asiatica, and different hierarchical responses of C. asiatica to different habitats and microsites with different herbaceous coverage were observed. Plastic response to heterogeneous habitat is stronger at smaller scale than that at larger scale.

    ZHU Zhi-Hong, LIU Jian-Xiu, WANG Xiao-An
    Chin J Plant Ecol. 2007, 31 (4):  588-598.  doi:10.17521/cjpe.2007.0075
    Abstract ( 3758 )   Full Text ( 5 )   PDF (445KB) ( 2185 )   Save
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    Phenotypic plasticity is the ability of a genotype to produce distinct phenotypes when exposed to different environments during its ontogeny. There is new strong evidence for the heritable nature of phenotypic plasticity, and variation in plasticity should thus be recognized as an integral component of evolution, but not as a factor that buffers and thereby constrains the action of selection. Clonal plants have both clonal modularity and organismic modularity. As a result, phenotypic selection in clonal plants is hierarchical. Modular hierarchy of clonal plants consists of three levels, the genet, ramet fragment and ramet levels. Modes of hierarchical selection and genotypic selection have been considered in studying natural selection in clonal plants. The hierarchical selection model treats each hierarchical level as a single level of phenotypic selection, and selection effects are determined by both the selective pressure on each level and ioteractions among levels. Net effects of multi-level phenotypic selection are transmitted finally to the succeeding generations through the ramet level. The genotypic selection model puts forward that clonal growth can lead to genetic variances between ramets within a genet. Then allele frequencies will change because of non-random mating within or among genets, leading to microevolution. In clonal plants, ramets may have the greatest phenotypic variation because it is the fundamental unit of sexual and asexual reproduction, whereas genets may have the lowest phenotypic variation because it is a relative stable unit. It is termed as the mode of hierarchical responses of phenotypic plasticity. The module of a plant has the greatest phenotypic plasticity, and phenotypic plasticity is not a whole-plant response but a property of module triggered by local environmental conditions. Therefore, the mode of hierarchical responses of phenotypic plasticity in clonal plants may be universal. If the mode indicates a response mode of adaptive plasticity of different `individuals' in modular hierarchy, we can predict that: 1) the effects of natural selection on clonal plants should be shown first at ramet level and will ultimately result in microevolution as predicted by both hierarchical selection and genotypic selection models and 2) the conservativeness in evolutionary changes may be greater in clonal plants than in non-clonal plants because of lower ability of sexual reproduction and high degree of physiological integration. The most promising directions for future research include areas such as those demonstrating the universality of hierarchical responses to natural selection in clonal plants and revealing the mechanisms of hierarchical responses.

    CAI Ying, GUAN Bao-Hua, AN Shu-Qing, SHEN Rui-Ling, JIANG Jin-Hui, DONG Lei
    Chin J Plant Ecol. 2007, 31 (4):  599-606.  doi:10.17521/cjpe.2007.0076
    Abstract ( 2913 )   Full Text ( 2 )   PDF (532KB) ( 1348 )   Save
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    Aims Trapa bicornis is a clonal floating macrophyte that dominates several lakes in China. Due to eutrophication, the distribution of T. bicornis is shrinking, and T. bicornis has disappeared in some lakes. Our objectives were to investigate the effects of sediment phosphorus concentration (SP), plant density (PD) and their interaction on the plasticity of T. bicornis and examine whether plasticity could promote ecological adaptation in eutrophic environments.
    Methods In a controlled factorial experiment, we grew artificial populations of T. bicornis in low, medium and high PD (4, 8 and 12 individuals per container, respectively) under low, medium and high SP. We harvested all plants after six weeks and measured the dry mass for each plant part.
    Important findings SP significantly affected leaf, stem, green root, anchoring root and total plant phosphorus concentrations as well as number of main rosettes of trullate floating leaves, special green root length and special anchoring root length of T. bicornis, but PD did not significantly affect any growth or ecophysiological traits. With increasing SP, plant phosphorus concentration increased. Number of main rosettes of trullate floating leaves of T. bicornis was the largest at low SP and low PD, leaf mass ratio at medium SP and high PD, special green root length at high SP and medium PD, and special anchoring root length at high SP and high PD. SP, PD and their interaction altered some of the allometric relationships between leaf, stem, green root, anchoring root and total biomass. Morphological and ecophysiological traits mostly affected by SP and high PD may increase the ecological adaptability of T. bicornis under eutrophic conditions caused mainly by phosphorus.

    ZHAO Lei, ZHI Ying-Biao, LI Hong-Li, AN Shu-Qing, DENG Zi-Fa, ZHOU Chang-Fang
    Chin J Plant Ecol. 2007, 31 (4):  607-612.  doi:10.17521/cjpe.2007.0077
    Abstract ( 2985 )   Full Text ( 3 )   PDF (260KB) ( 1652 )   Save
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    Aims Spartina anglica, a world-wide invasive species introduced from Europe in 1963, rapidly increased in coastal China before the 1990s and thereafter drastically declined. Researchers hypothesized that small initial clone numbers might be responsible for the decline. We investigate the effect of different initial clone numbers on morphological plasticity and biomass allocation of S. anglica.
    Methods From May to November 2005, field experiments were conducted in S. anglica vegetation located along the coast of the Yellow Sea (32°34'-34°28' N, 119°48'-120°56' E). We set up three treatments with one, three, and five initial clones. For each plant, we measured height, stem diameter, leaf thickness, leaf area, number of leaves, spacer length and branching intensity as morphological parameters and number of ramets, rhizomes and rhizome nodes and total length of rhizomes as growth traits. We also analyzed biomass accumulation, allocation and allometric growth of S. anglica.
    Important findings With greater initial clone number, branching intensity, total biomass, above-ground biomass, below-ground and rhizome biomass increased significantly, but initial clone number did not affect root biomass and spacer length. Plants in multi-clone treatments tended to allocate more resource to rhizomes, while those in the single-clone treatment tended to allocate more resource to roots. Results indicated that S. anglica plants with multiple clones had more effective asexual reproduction than plants with a single clone. Because most environments likely were invaded by a single clone and then added additional clones, we hypothesize that the main reproduction strategy of S. anglica has changed from sexual to asexual reproduction, which may account for the population dieback since the 1990s in China.

    LIANG Shi-Chu, ZHANG Shu-Min, YU Fei-Hai, DONG Ming
    Chin J Plant Ecol. 2007, 31 (4):  613-618.  doi:10.17521/cjpe.2007.0078
    Abstract ( 2881 )   Full Text ( 2 )   PDF (270KB) ( 1280 )   Save
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    Aims Comparison of spatial patterns of clonal plant populations and soil variables has received little attention in ecological studies, although many papers implicitly assume that plant spatial distribution is controlled by soil variables acting at small scales. Our main aim was to investigate small-scale spatial cross-correlation between population variables of clonal plant species and soil available phosphorus.
    Methods We investigated a ramet population of Potentilla reptans var. sericophylla in Dongling Mountain Area in Beijing to investigate the degree and scales of patchiness of soil available phosphorus and to determine spatial similarities between population variables and available phosphorus. Spatial soil and plant samples were collected in a plot of 336 cm× 96 cm. Semivariogram and cross-correlogram were applied to characterize spatial patterns.
    Important findings Soil available phosphorus had clear patchy structure with the spatial autocorrelation range of 37.8 cm. Cross-correlation between measured variables of the ramet population of P. reptans var. sericophylla and soil available phosphorus was negatively significant at a lag interval of 75-110 cm, but not significant at a lag interval of 110-165 cm. There was significant positive correlation between soil available phosphorus and number of ramets and leaves and biomass of stolons at a lag interval <50 cm and for biomass of roots at a lag interval <30 cm. Resource sharing and selective placement of ramets in favorable micro-habitats may be important ecological strategies for Potentilla reptans var. sericophylla to exploit small-scale soil resources that are heterogeneously distributed.

    ZHANG Li-Li, DONG Ming, LI Ren-Qiang, WANG Yan-Hong, CUI Qing-Guo, HE Wei-Ming
    Chin J Plant Ecol. 2007, 31 (4):  619-624.  doi:10.17521/cjpe.2007.0079
    Abstract ( 2653 )   Full Text ( 5 )   PDF (369KB) ( 1614 )   Save
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    Aims The connected fragments of clonal plants often grow in different soil-nutrient patches, and clonal integration can modify the plasticity of these connected clonal fragments in diverse ways. We address how nutrient patch contrast modifies intensity and direction of clonal integration.
    Methods In a common garden experiment, we planted clonal fragments of Glechoma longituba in four nutrient-patch contrast conditions: no (control), low, medium and high contrast. Water was supplied when necessary. We measured physiological traits at peak growth and harvested all plant materials at the end of the experiment, which ran from July 19 through September 30, 2005. Data were analyzed with SPSS software.
    Important findings Clonal integration in gas exchange, water potential, fluorescence, growth and biomass allocation differed among nutrient patch contrast treatments. Higher contrast had smaller integration in both gas exchange and dark fluorescence response and greater integration in leaf water potential. Direction of clonal integration for some characteristics also different among treatments, indicating that the threshold of soil-nutrient patch contrast might play a fundamental role in determining integration direction. Clonal integration had far broader effects on growth and allocation than physiological traits. We infer that nutrient-patch contrast may modify the intensity and direction of clonal integration, which in turn can shape the phenotypic plasticity of clonal plants.

    WEI Xiao-Hui, YIN Dong-Sheng, ZHU Ning
    Chin J Plant Ecol. 2007, 31 (4):  625-629.  doi:10.17521/cjpe.2007.0080
    Abstract ( 2410 )   Full Text ( 2 )   PDF (217KB) ( 1097 )   Save
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    Aims Few studies have investigated the clonal growth patterns of shrubs. Physocarpus amurensis is a rhizomatous, endangered shrub with an extremely narrow distribution in Heilongjiang Province of China. Its sexual reproductive capacity is low, and seedling recruitment has rarely been observed under natural conditions. Therefore, clonal growth seems to be important in maintaining populations. Morphological plasticity is important for clonal plants to exploit environmental heterogeneity. This study investigates the clonal architecture and ramet growth dynamics of P. amurensis to provide useful information for protection of this species.
    Methods Variations in clonal architecture were studied by field investigation and laboratory analysis: architectural form of rhizomes, configuration characteristics of rhizomes, variations in diameters of rhizomata with increasing rhizome length, and branching angle between rhizomes.
    Important findings The architectural form of rhizomes of P. amurensis belongs to the sparse guerrilla linear system. Ramets and rhizomes per clone averaged 6±2 and 9.33±3.48, respectively. The distribution of diameters of rhizomata with increasing rhizome length was parabolic. Branching angle between rhizomes was consistent, usually 30° and 70°. Physocarpus amurensis forms large ramet systems with several interconnected ramets, covering a large area. This may be an adaptation to exploiting different habitats, allowing exploration of open space, which may ensure population survival and evolution.

    ZHANG Ying, JIA Zhi-Bin, YANG Chi
    Chin J Plant Ecol. 2007, 31 (4):  630-636.  doi:10.17521/cjpe.2007.0081
    Abstract ( 2526 )   Full Text ( 2 )   PDF (348KB) ( 1187 )   Save
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    Aims The relationship between clonal growth and ecological adaptation is a central issue in clonal plant population ecology, but few studies have examined of growth patterns of small half-shrubs. Thymus serpyllum var. asiaticus is a dwarf half-shrub with creeping stems. Soil erosion is a serious problem in the “pisha"-sandstone area, such as the Huangfuchuan watershed, where T. serpyllum var. asiaticus can form a mono-dominant community and help maintain ecosystem stability. Understanding clonal growth characteristics of T. serpyllum var. asiaticus, therefore, is potentially helpful for vegetation restoration in this area.
    Methods We sampled T. serpyllum var. asiaticus clones consisting of mother, daughter and granddaughter ramets from May to September 2004 in Huangfuchuan watershed. For each clone, we counted numbers of roots, stems and branches and measured biomass of roots, stems, branches, leaves and flowers. We examined monthly changes in biomass allocation of the different ramets.
    Important findings Compared with the daughter and granddaughter ramets, the mother ramets of T. serpyllum var. asiaticus were bigger with more complex structure, biomass and number of modules. Mother ramets had largest biomass allocation to roots and much smaller to leaves. For the daughter and granddaughter ramets, biomass allocation to leaves was largest and that to roots was smaller. Differences in biomass allocation patterns between mother and daughter (and granddaughter) ramets may reflect different ramet functions. Mother ramets may be specialized for water and nutrient absorption, while daughter and granddaughter ramets may be specialized for photosynthesis, a phenomenon called `division of labor'. According to changes in biomass allocation to branches, stems and flowers from May to September, the module growth of mother and daughter ramets was similar, but differed from that of granddaughter ramets. Findings may reflect different physiological integrations of ramets.

    SONG Li-Xia, TAO Jian-Ping, RAN Chun-Yan, YU Xiao-Hong, WANG Yong-Jian, LI Yuan
    Chin J Plant Ecol. 2007, 31 (4):  637-644.  doi:10.17521/cjpe.2007.0082
    Abstract ( 2894 )   Full Text ( 1 )   PDF (389KB) ( 1279 )   Save
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    Aims Fargesia nitida, one of the Giant Panda's main food sources, is adapted to varied canopy conditions through changes in morphology and/or biomass allocation. We hypothesized that changes in clonal regeneration may be another way for this plant to be adapted to different canopy conditions.
    Methods From August to September 2005, we measured the number, size and rhizome size of new shoots and the age and size of the parent ramet in four canopy conditions: forest understory (FU), moderate gap (MG), large gap (LG) and forest edge wilderness (FEW) in an Abies faxoniana forest in Wolong Nature Reserve in the western Sichuan, China. The data were analyzed by One-Way ANOVA, independent-sample t-test and regression.
    Important findings The density of surviving new shoots was lower in the FU than that in the other three canopy conditions. With decreasing canopy cover (i.e., from FU to MG to LG), the number of surviving new shoots per genet increased. At the ramet level, the mean height, basal diameter, and biomass of surviving new shoots and parent ramet were significantly different (p<0.01) and increased as canopy cover decreased. In the different canopy conditions, the number of new shoots cloned by two-year-old primary parent ramets was the largest, but mean ages of parent ramets were not significantly different. There were no significant differences in average number and basal diameter of surviving new shoots reproduced by primary parent ramets with different ages in the same environment. In each canopy condition, the basal diameter of primary and secondary parent ramets were both positively correlated with basal diameter of surviving new shoots, but the effect of the primary parent ramets on surviving new shoots was stronger than that of the secondary parent ramets. The rhizome diameter of new shoots was positively correlated with the basal diameter of new shoots and primary parent ramet, but the rhizome length of surviving new shoots was not significantly correlated with basal diameter of the primary parent ramet. These results indicated that the clonal growth features exhibited significant differences strongly correlated with canopy conditions.

    CHEN Lin, DENG Zi-Fa, AN Shu-Qing, ZHAO Cong-Jiao, ZHOU Chang-Fang, ZHI Ying-Biao
    Chin J Plant Ecol. 2007, 31 (4):  645-651.  doi:10.17521/cjpe.2007.0083
    Abstract ( 2611 )   Full Text ( 3 )   PDF (367KB) ( 1240 )   Save
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    Aims Spartina alterniflora is a world-wide, notorious invasive species that has colonized large areas in coastal China since it was introduced in 1979. Its wide range of salinity tolerance and resistance to salinity stress contribute to its invasiveness. However, if its mechanism of salt tolerance can be degraded in freshwater or disturbed by alternating irrigation between fresh and salt water, the invasiveness of S. alterniflora may be reduced.
    Methods We exposed S. alterniflora for three months to six irrigation treatments: single irrigation with freshwater (D) or saltwater (X), single alternating irrigation with freshwater and saltwater (DX and XD) and double alternating irrigation (DXD and XDX).
    Important findings With only freshwater, biomass accumulation and asexual reproduction of S. alterniflora was significantly higher than that with only saltwater. Alternating irrigation between fresh and salt water significantly affected biomass, number of propagules and flowering stems, with much stronger effects in the double alternating irrigation treatment. But irrigation treatment displayed weak effects on the root-shoot ratio, stem weight ratio, leaf weight ratio and rhizome weight ratio, although they strongly affected the root weight ratio. Results indicate that single irrigation with freshwater may benefit the biomass accumulation of S. alterniflora and make the species apt to adopt asexual reproduction. However, alternating irrigation between fresh and salt water may restrain biomass accumulation and both sexual and asexual reproduction.

    ZHANG Shu-Min, YU Fei-Hai, DONG Ming
    Chin J Plant Ecol. 2007, 31 (4):  652-657.  doi:10.17521/cjpe.2007.0084
    Abstract ( 2671 )   Full Text ( 2 )   PDF (288KB) ( 1417 )   Save
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    Aims Plasticity in biomass allocation of plants under different growing conditions is often assumed to be adaptive. Biomass allocation patterns in clonal plants are usually different from those in non-clonal plants due to clonal architecture and clonal morphology. de Kroon and Schieving (1991) published a model to predict the likely pattern of biomass allocation to spacers (i.e., stolons or rhizomes) as resource supply varies. The model predicted that under moderate resource levels, clonal plants would allocate more biomass to spacers to efficiently utilize resources. The aim of this study is to experimentally test this prediction.
    Methods In a greenhouse experiment, Potentilla reptans var. sericophylla plants were subjected to eight levels (i.e., N1 to N8 in decreasing order) of nutrient supply. N1 was equivalent to 600 kg nitrogen as NH4NO3, 240 kg phosphorus as NaH2PO4 and 600 kg K as KCl per ha per year. N2 to N8 were 50%, 25%, 12.5%, 6.25%, 3.13%, 1.57% and 0 of N1, respectively. The experiment started on April 6, 2003 and ended on June 3, 2003.
    Important findings Potentilla reptans var. sericophylla had greater biomass, produced more stolons and had longer stolon internodes at moderate levels (i.e., N3 and N4 treatments) of nutrient supply. Biomass allocation to different plant organs (roots, stolons, laminae and petioles) responded greatly to nutrient treatments. With decreasing nutrient supply, biomass allocation to laminae and petioles decreased, whereas that to roots increased. Biomass allocation to stolons tended to be the highest at moderate levels (N3, N4) of nutrient supply and became smaller at both lower and higher nutrient conditions. Patterns of biomass allocation to stolons in P. reptans var. sericophylla under different levels of nutrient supply agree with the model prediction of de Kroon and Schieving (1991), suggesting that allocating more biomass to spacers (i.e., stolons or rhizomes) at moderate nutrient levels enables clonal plants to efficiently utilize resources.

    ZHU Ya-Juan, ALATEN Bao, DONG Ming, HUANG Zhen-Yin
    Chin J Plant Ecol. 2007, 31 (4):  658-664.  doi:10.17521/cjpe.2007.0085
    Abstract ( 2855 )   Full Text ( 2 )   PDF (502KB) ( 1225 )   Save
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    Aims Hedysarum laeve is a rhizomatous perennial semi-shrub, which reproduces both sexually and clonally in natural populations. Study of reproduction trade-off of this species could provide theoretical foundation for the management of natural grassland. The specific goal of this study was to determine if there is a trade-off between sexual and clonal reproduction in H. laeve natural population in response to water and nutrient supplies.
    Methods During the growing season of June to September 2005, we conducted two field experiments in Mu-Us Sandland using 1 m×1 m plots. Different amounts of water were added to the plots to imitate 0, 16, 32 and 64 mm of precipitation. Nutrient additions were 0, 30, 60, 90 and 120 g. The biomass of H. laeve ramets in each plot was measured in late September 2005.
    Important findings Increasing water supply decreased both biomass and biomass allocation to flowers, fruit sets and rhizomes, whereas it increased biomass and biomass allocation to clonal ramet shoots. Within increasing water supply, biomass allocation to sexual reproduction decreased, whereas biomass allocation to clonal reproduction did not change. However, increasing water supply increased biomass allocation to ramet shoots but decreased that to ramet rhizomes. Therefore, increase in water supply inhibited sexual reproduction and thus changed the biomass allocation to clonal reproduction. Increasing nutrient supply increased fruit biomass and decreased biomass of shoots, leaves and rhizomes of clonal ramets, but did not affect biomass of other parts. With increasing nutrient supply, biomass allocation to fruits increased, whereas biomass allocation to leaves and shoots of clonal ramets decreased. Therefore, increase in nutrient supply enhanced sexual reproduction, but reduced clonal reproduction. We conclude that there is a trade-off between the sexual and clonal reproduction in H. laeve population in responses to water and nutrient supplies. The plastic responses of sexual and clonal reproduction of H. laeve populations to environmental factors may be an adaptation to heterogeneous environments.

    SHEN Rui-Ling, GUAN Bao-Hua, CAI Ying, AN Shu-Qing, JIANG Jin-Hui, DONG Lei
    Chin J Plant Ecol. 2007, 31 (4):  665-672.  doi:10.17521/cjpe.2007.0086
    Abstract ( 2591 )   Full Text ( 1 )   PDF (434KB) ( 1202 )   Save
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    Aims Plants show phenotypic plasticity in response to changing environments via variations of morphological and ecophysiological traits, and this plasticity can increase invasiveness. Plasticity, rather than genetic diversity, made Alternanthera philoxeroides more invasive, but its plasticity to sediment phosphorus concentration of invaded habitats was undocumented. This study addresses plasticity of A. philoxeroides to sediment phosphorus concentration and planting density and whether plasticity increases invasiveness.
    Methods In a controlled factorial experiment, we grew artificial populations of A. philoxeroides at low and high densities (four and eight individuals per container, respectively) under three levels (low, median, high) of sediment phosphorus concentrations. All plants were harvested after six weeks, and dry mass of leaves, stems and roots were measured.
    Important findings Under low planting density, leaf mass and number, stem mass and length, branch number, and total biomass of A. philoxeroides were larger at high than low or median sediment phosphorus concentration. Under high planting density, leaf number, stem length and special stem length were greater at high than at low or median sediment phosphorus concentration. Leaf, stem, root and total phosphorus concentrations in A. philoxeroides increased significantly with increasing the sediment phosphorus concentration. Leaf mass ratio was also affected by sediment phosphorus concentration, and stem mass, special stem length, leaf and total phosphorus concentration were significantly affected by planting density. Results imply that morphological and ecophysiological traits of A. philoxeroides were altered by sediment phosphorus concentration and that high sediment phosphorus may strengthen the invasiveness of A. philoxeroides.

    WANG Zheng-Wen
    Chin J Plant Ecol. 2007, 31 (4):  673-679.  doi:10.17521/cjpe.2007.0087
    Abstract ( 2957 )   Full Text ( 1 )   PDF (344KB) ( 1274 )   Save
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    Aims This study of the rhizomatous clonal grass Leymus chinensis examines: 1) temporal variations of water-soluble carbohydrate (WSC) in shoots and rhizomes and their responses to defoliation; 2) WSC concentrations in different plant parts at specific growth stages; 3) links between variations of WSC concentration in aboveground shoots, belowground shoots and rhizomes; and 4) the significance of carbohydrate reserves for the growth and survival of ramets and the whole genet of the plant.
    Methods A control (intact) and three treatments as one, three and five defoliations were used in a field experiment. All defoliations left plants 15 cm high. Shoots and rhizomes were sampled in different quadrats every 10 days. WSC carbohydrate concentrations in different plant parts were determined with HPLC (high performance liquid chromatography). ANOVA was used to detect differences among treatments in temporal dynamics of WSC contents.
    Important findings The marked reduction of WSC concentration in the control in a stage of rapid growth was attributed to higher growth rate and thus higher respiration rate in the carbon metabolism of leaves, while WSC concentrations in defoliation treatments were less reduced or increased under frequent defoliation, mainly due to reduction of total respiration with leaf loss. Single defoliation did not affect the final WSC concentration in aboveground shoots, but successive defoliations did. The more frequent the defoliations, the more rapid the transfer of carbohydrate from aboveground shoots to belowground shoots or rhizomes in response to declining air temperature. WSC concentrations in belowground shoots were slightly more stable than in aboveground shoots, probably because belowground shoots functioned as storage organs for tiller buds and partly for some nutrient or assimilate. WSC in rhizomes must be transported into aboveground shoots to supply them, and intensive growth depletes WSC; however, such depletion can be mitigated when clonal integration in intact neighborhood ramets results in replenishment of defoliated ramets (usually at the frequent defoliation treatment).

    LI Jun-Min, DONG Ming, ZHONG Zhang-Cheng
    Chin J Plant Ecol. 2007, 31 (4):  680-688.  doi:10.17521/cjpe.2007.0088
    Abstract ( 2649 )   Full Text ( 5 )   PDF (385KB) ( 1941 )   Save
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    Aims Genetic changes after introduction may contribute to the success of invasive plants. Our objective was to measure genetic diversity and genetic differentiation in the invasive Mikania micrantha in order to assess its invasive prospects.
    Methods Inter-simple sequence repeat (ISSR) markers were used to analyze genetic diversity and genetic differentiation in eight populations of M. micrantha.
    Important findings The 12 ISSR primers used in this study produced 171 loci, of which 103 were polymorphic. At the species level, the percentage of polymorphic loci (P) was 60.23%, Shannon's information index (I) 0.281 8 and Nei's gene diversity (h) 0.184 9, indicating high genetic diversity in M. micrantha. Analysis of molecular variance (AMOVA) revealed that a high proportion (36.49%) of the total genetic variation was partitioned among populations, suggesting significant genetic differentiations among the eight populations of M. micrantha. Gene differentiation coefficient (GST) among populations was 0.352 4, and gene flow among populations was 0.918 7. Average genetic similarity of the eight populations was 0.915 5, while average genetic distance was 0.088 4. Using unweighted pair group method arithmetic average (UPGMA), the eight populations were clustered into two groups: the two populations on Neilingding Island were one group and the other six from mainland China were the other.

    Jonathan M. Frantz, Nilton N. Cometti, Marc W. van Iersel, Bruce Bugbee
    Chin J Plant Ecol. 2007, 31 (4):  695-710.  doi:10.17521/cjpe.2007.0090
    Abstract ( 2509 )   Full Text ( 4 )   PDF (1011KB) ( 999 )   Save
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    Aims Changes in light and temperature are among the most common and most profound environmental perturbations. The independent effects of light and temperature on photosynthesis and respiration are well studied in single leaves, but are less well studied in whole plants. The short and long term influence of light and temperature on carbon use efficiency is also poorly understood, and is commonly modeled to remain constant over a wide range of conditions. We sought to determine the primary effects of changing light at two growth temperatures on photosynthesis, respiration, and their balance, as defined by carbon use efficiency.
    Methods We separated respiration into growth and maintenance components using whole-canopy gas-exchange in an elevated CO2 environment in a controlled environment, and supplemented that information with tissue analysis.
    Important findings Decreases in light level decreased carbon use efficiency through a reduction in the maintenance coefficient, increased the growth coefficient, and reduced partitioning of N in protein. Growth temperature did not significantly affect either maintenance or growth respiration coefficients, suggesting that long-term temperature responses can differ greatly from short-term observations.

    ZUO Wen-Yun, LAO Ni, GENG Yu-Ying, MA Ke-Pin
    Chin J Plant Ecol. 2007, 31 (4):  711-719.  doi:10.17521/cjpe.2007.0091
    Abstract ( 3276 )   Full Text ( 4 )   PDF (408KB) ( 1514 )   Save
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    Aims The most common method to build a predictive model of species' potential distribution is to use environmental factors, because they strongly affect species distribution. Unfortunately, most predictive models suffer from the “high dimension small sample size" problem, and cannot give satisfactory results in many cases. Support vector machine (SVM), which is based on structural risk minimization principle, has proven to be especially suitable for such data by both theory and abundant applications. Our objective was to implement a new predictive system of species' potential distribution based on the SVM method.
    Methods We performed a country-scale case study using 20 Chinese endemic species of Rhododendron, employing herbarium specimen data and 11 layers of 1 km×1 km digital environmental grid data. Through expert evaluation and receiver operator characteristic (ROC) curve, we compared SVM predictions with those of a commonly used modeling method, the genetic algorithm for rule-set prediction (GARP).
    Important findings All scores of SVM's prediction are higher than GARP's in expert evaluation. For the statistical analysis of ROC curve, almost all the area under the curve (AUC) determinations of SVM are larger than that of GARP. Furthermore, SVM's prediction speed is much faster than GARP's. Through our experiment, comprehensive evaluation proved that SVM is much better than GARP in terms of both performance and accuracy on the “high dimension small sample size" problem.

    ZHANG Zhi-Meng, DAI Liang-Xiang, HU Chang-Hao, DONG Shu-Ting, WANG Kong-Jun, NING Tang-Yuan
    Chin J Plant Ecol. 2007, 31 (4):  720-728.  doi:10.17521/cjpe.2007.0092
    Abstract ( 2943 )   Full Text ( 1 )   PDF (544KB) ( 1199 )   Save
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    Aims The biosynthesis of maize protein, which is positively correlated to maize grain quality, is controlled by nitrate reductase (NRase), glutamine synthetase (GS), and glutamate dehydrogenase (GDH), which are affected by genetics and environment. Therefore, cultivation methods and environment affect grain quality in maize; however, there are few reports of the effects of soil water on maize grain quality and corresponding enzyme activities.
    Methods The experiment was carried out in pool culture within a rain-proof shelter using normal maize (Yedan 22) and high oil maize (Gaoyou 115). There were three water treatments: no irrigation after anthesis, irrigation once after anthesis (at grain filling period) and irrigation three times after anthesis (at grain filling period, milky period and wax period).
    Important findings Grain protein was higher in Gaoyou115 than Yedan22, and its component contents increased with increasing water supply. With different water supply, the activities of NRase, GS in leaves and GS, GDH in grains exhibited the same trends in the two types of maize. The activity of NRase decreased, and the activities of GS and GDH had unimodal curves, peaking 20 to 40 days after pollination. The activities of these enzymes increased with increased water supply. However, the activity of NRase in leaves of Yedan22 was higher than in Gaoyou115, while the activities of GS in leaves and GDH in grains were reversed, resulting in lower protein content in grains of Yedan22 than in Gaoyou115. The NRase and GS activities in maize leaves did not match grain protein content. Soil water condition was closely related with the activities of GS and GDH in ear leaves and grains of different types of maize.

    SONG Xiao-Ling, HUANGFU Chao-He, QIANG Sheng
    Chin J Plant Ecol. 2007, 31 (4):  729-737.  doi:10.17521/cjpe.2007.0093
    Abstract ( 3069 )   Full Text ( 1 )   PDF (345KB) ( 1221 )   Save
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    Aims Wild rape (Brassica juncea var. gracilis), a wild relative of oilseed rape (B. napus), was chosen for a case study because gene flow from herbicide-resistant oilseed rape to wild rape rarely has been explored. We asked a) are transgenic herbicide-resistant oilseed rape and wild rape sexually compatible, b) is the fitness of their F1 improved and c) is gene flow possible?
    Methods We used hand pollination to test sexual compatibility and examined resistance of the F1 by applying herbicide of 2 000 μg a.i.·kg-1 with 0.1 L·m-2 volume at 3-4 leaf stage twice and by PCR and examining vegetative growth, pollen viability and seed setting rate. Crossing from herbicide-resistant oilseed rape to wild rape also was tested under open pollination.
    Important findings Indexes of sexual compatibility of wild rape×glufosinate-tolerant oilseed and wild rape×glyphosate-tolerant oilseed were 13.87 and 13.83, respectively, under hand pollination, and these indexes were not significantly different from that of the female parent under self pollination and open pollination. All F1 were significantly resistant to the corresponding herbicide. Moreover, herbicide-resistant gene of F1 was confirmed by PCR and F1 of wild rape×glufosinate-resistant oilseed and wild rape×glyphosate-resistant oilseed produced 426 bp and 931 bp identical special band, respectively. The fitness of the F1 changed compared with that of the female parent. The germination rate of the F1 was similar with that of the female parent, >98%. Due to taller individuals and larger leaves, the vegetative growth of the F1 was much better than that of the female parent. However, pollen viabilities of both kinds of F1 were only half that of the female parent. Furthermore, the seed number per silique of the F1 was very low, only 0.59 and 0.58 seeds per silique, respectively. The cross rate of wild rape×glufosinate-resistant and wild rape×glyphosate-resistant was 0.02% and 0.01%, respectively, under open pollination. Our study suggests the possibility of gene flow from transgenic rape to wild rape. The possibilities of gene flow from the two herbicide-resistant transgenic oilseed rapes to wild rape were similar under hand pollination or open pollination. However, the effect of gene flow from transgenic herbicide-resistant oilseed to wild rape needs further research.

    XU Zhen-Zhu, ZHOU Guang-Sheng
    Chin J Plant Ecol. 2007, 31 (4):  738-747.  doi:10.17521/cjpe.2007.0094
    Abstract ( 2500 )   Full Text ( 7 )   PDF (477KB) ( 2232 )   Save
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    Globally elevated temperatures and changed precipitation distributions may lead to deficits of fresh water that reduce crop yields and degrade natural ecosystems. Plant carbon (C) and nitrogen (N) metabolism and its abiotic environmental regulation are responsible for net primary productivity and plant nutrient status. We review the relationship between C and N and regulation by environmental factors such as temperature, water moisture and CO2 enrichment at multiple levels of plant organization, including molecule, tissue, organ, whole plant and ecosystem. For cereal crops including wheat and rice, grain N mainly includes: 1) N reallocated in vegetative organs before anthesis, and 2) N absorbed from soil after anthesis. Their proportions depend on the activity and size of grains as an N sink and species and cultivars, affecting the grain yield and quality. Leaf N level can explain 45%-75% of leaf photosynthesis, and 71%-88% of leaf N can be allocated into protein, with Rubisco, the key enzyme for photosynthesis, accounting for 30%-50% of total leaf soluble protein, making it the protein using most N. Furthermore, the N proportions among the photosynthetic organs and the ratio between soluble sugar and starch may be associated with the Rubisco gene. Therefore, plant N level may be assessed by photosynthetic capacity.
    Many studies have demonstrated that drought can promote C allocation to below-ground parts of plants, increasing root:shoot biomass ratio. There is, however, evidence that this enhancement of roots due to moderate drought can be negated by severe drought. On the other hand, drought also increases N concentration in sink organs, such as wheat grains, and decreases mature leaf N concentration, decreasing leaf net photosynthetic rate. However, high temperature does not significantly increase C allocation to roots, but may decrease leaf N concentration and affect Rubisco level. Thus, a decline of photosynthetic capacity induced by above optimal temperature, particularly at night, may be ascribed to an adverse effect on photosystem Ⅱ (PSⅡ). Generally, elevated CO2 dilutes plant tissue N, leading to a lower C:N ratio that may come from the effect on Rubisco expression. Whole ecosystem N allocation and cycle can be affected by elevated CO2, thereby changing ecosystem structure and function. The interaction between severe drought and high temperature can lead to a decrease in leaf N, reducing plant C-fixing ability, depending on the time and severity of stresses. Under high CO2 concentration and drought, the C allocation into below-ground parts can be enhanced and the C:N ratio may increase. The interaction between elevated CO2 and high temperature can alter plant tissue N allocation, with elevated CO2 increasing CO2 site activity of Rubisco and decreasing N investment in photosynthetic apparatus, but high temperature increasing O2 site activity of Rubisco and increasing N investment. Nevertheless, under global change conditions, the combined effects from various stress factors are complex, and may include both positive and negative relationships. Research is urgently needed to 1) elucidate plant C and N allocation models from molecular to ecosystem levels; 2) address synergistic effects of multiple environmental stresses; 3) predict C and N allocation based on different global change scenarios; 4) quantify the threshold for change in C and N allocation in response to global change; and 5) strengthen knowledge of the key role of C and N allocation in agricultural and forest productivity and conservation of natural ecosystems.

    WANG Chang-Quan, ZHAO Ji-Qiang, CHEN Min, WANG Bao-Shan
    Chin J Plant Ecol. 2007, 31 (4):  748-752.  doi:10.17521/cjpe.2007.0095
    Abstract ( 2729 )   Full Text ( 4 )   PDF (199KB) ( 1724 )   Save
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    Aims Betalains are an important class of water-soluble pigments that comprise the red-violet betacyanins and the yellow betaxanthins and accumulate in most families of the Caryophyllales and some higher fungi. However, little is known about the regulation of betalain bio-synthesis by environmental factors in higher plants. Our objective is to explore the mechanism and the biological role of betacyanin accumulation induced by dark in leaves of the C3 halophyte Suaeda salsa.
    Methods Seeds of S. salsa were cultured in 24 h dark and 14 h light/10 h dark, and watered with 0, 0.2% and 1.0% H2O2 nutrient solution. Seedlings were harvested three days later and assayed for betacyanin content, H2O2 content, activity of catalase (CAT) and superoxide dismutase (SOD) in leaves.
    Important findings Darkness significantly enhanced H2O2 content, betacyanin content, activity of SOD and CAT in S. salsa leaves. Application of different concentrations of H2O2 to the culture solution increased H2O2 content, betacyanin content, activity of SOD and CAT compared to the dark treatment. Betacyanin content and H2O2 content in S. salsa leaves were closely related. Moreover, the scavenging superoxide ($\mathop{{O}}_{2}^{{\mathop{}-{\ •}^{-}}}$) ability of the betacyanins from S. salsa leaves in vitro was lower than that of vitamin C, while the scavenging hydroxyl radical (·OH) ability of the betacyains was much higher than that of vitamin C. These results suggest that betacyanin accumulation in S. salsa leaves grown in dark is possibly induced via reactive oxygen species (ROS) such as H2O2 and that betacyanin is involved in alleviating damage caused by oxidative stress due to its high ROS scavenging ability.

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