Shifting effects of physiological integration on performance of a clonal plant during submergence and de-submergence

Background and Aims

Submergence and de-submergence are common phenomena encountered by riparian plants due to water level fluctuations, but little is known about the role of physiological integration in clonal plants (resource sharing between interconnected ramets) in their adaptation to such events. Using Alternanthera philoxeroides (alligator weed) as an example, this study tested the hypotheses that physiological integration will improve growth and photosynthetic capacity of submerged ramets during submergence and will promote their recovery following de-submergence.

Methods

Connected clones of A. philoxeroides, each consisting of two ramet systems and a stolon internode connecting them, were grown under control (both ramet systems untreated), half-submerged (one ramet system submerged and the other not submerged), fully submerged (both ramet systems submerged), half-shaded (one ramet system shaded and the other not shaded) and full-shaded (both ramet systems shaded) conditions for 30 d and then de-submerged/de-shaded for 20 d. The submerged plants were also shaded to very low light intensities, mimicking typical conditions in turbid floodwater.

Key Results

After 30 d of submergence, connections between submerged and non-submerged ramets significantly increased growth and carbohydrate accumulation of the submerged ramets, but decreased the growth of the non-submerged ramets. After 20 d of de-submergence, connections did not significantly affect the growth of either de-submerged or non-submerged ramets, but de-submerged ramets had high soluble sugar concentrations, suggesting high metabolic activities. The shift from significant effects of integration on both submerged and non-submerged ramets during the submergence period to little effect during the de-submergence period was due to the quick recovery of growth and photosynthesis. The effects of physiological integration were not found to be any stronger under submergence/de-submergence than under shading/de-shading.

Conclusions

The results indicate that it is not just the beneficial effects of physiological integration that are crucial to the survival of riparian clonal plants during periods of submergence, but also the ability to recover growth and photosynthesis rapidly after de-submergence, which thus allows them to spread.     

Effect of physiological integration in self/non-self genotype recognition on the clonal invader Carpobrotus edulis

Aims Biological invasions represent one of the most important threats to the conservation of biodiversity; however, the mechanisms underlying successful invaders remain unsolved. Many of the most aggressive invaders show clonal growth, and capacity for clonal integration has been pointed out recently as an important trait explaining the success of invasive plants. We aim to determine the role of physiological integration in the capacity for self/non-self genotype recognition in the clonal invader Carpobrotus edulis and the implications of this capacity for the expansion of this aggressive invader.Methods We used connected and severed ramets of identical or different genotype and we determined the capacity for self/non-self recognition by comparing changes in biomass partitioning to avoid competition for resources between pairs of ramets.Important findings Physiological integration allowed self/non-self genotype recognition in the invader C. edulis. Results showed a significant effect of physiological integration on the biomass allocated to roots by genetically identical ramets: older ramets specialize in acquisition of soil-based resources and younger ramets specialize in lateral expansion. This specialization could be considered a form of division of labour, which reduce intra-genotype competition. This is the first evidence that division of labour could be interpreted as a form of self/non-self recognition between genetically identical ramets. Capacity for self/non-self discrimination could contribute to increase the colonization capacity of the aggressive invader C. edulis. This is the first study showing an association between self/non-self recognition and invasiveness in a clonal plant.     

Differences in physiological integration between invasive and noninvasive introduced clonal species of Carpobrotus

AimsClonal growth is associated with invasiveness in introduced plant species, but few studies have compared invasive and noninvasive introduced clonal species to investigate which clonal traits may underlie invasiveness. To test the hypothesis that greater capacity to increase clonal growthviaphysiological integration of connected ramets increases invasiveness in clonal plants, we compared the effects of severing connections on accumulation of mass in the two species of the creeping, succulent, perennial, herbaceous genusCarpobrotusthat have been introduced on sand dunes along the Pacific Coast of northern California, the highly invasive speciesCarpobrotus edulisand the co-occurring, noninvasive speciesCarpobrotus chilensis.     

植物克隆整合生态效应及潜在应用

克隆植物因特殊的克隆整合和空间拓展特性,在异质生境下展示出较高的生态适应性及适合度,这是其广泛存在于各类生态系统的一个重要原因。目前对克隆整合在个体或种群水平的生态学效应已有较深认识,而对群落及生态系统的影响及作用机制则明显关注不足。前期研究表明,克隆整合对土壤理化性质、根际微生物及个体竞争力均有显著影响,从而有利于克隆植物的成功入侵、生境修复及植被重建等。对群落及生态系统水平的克隆整合生态学效应的研究进行归纳和总结,分析了克隆整合对植物群落结构和生产力、根际微生物和土壤动物、生态系统碳固持、养分循环等的影响;阐释了克隆整合及空间拓展特性对退化生态系统的修复及作用机制,并指出今后克隆整合的研究应同时考虑微观(根际过程)和宏观(群落及生态系统)层次的效应以及短期与长期的效应。可将克隆整合与植物-土壤反馈等其他生态过程相联系,综合探究克隆整合的生态学意义。     

Genetic Allee effects on performance, plasticity and developmental stability in a clonal plant

Negative effects of small population size on fitness, so-called Allee effects, may threaten population persistence even in intact habitat remnants. We studied genotypes of 14 isolated populations of the clonal plant Ranunculus reptans, for which molecular genetic (RAPD-) variability is higher for large than for small populations. In a competition-free greenhouse environment vegetative offspring of genotypes from large populations produced more rosettes and flowers, indicating higher fitness. Within-genotype coefficients of variation in performance traits, indicating developmental instability, were lower for genotypes from populations with higher RAPD-variability. In competition with a taller grass, we found relative reduction in leaf length less pronounced for plants from large populations, suggesting higher adaptive plasticity. Our experimental study of a plant with predominantly vegetative reproduction suggests, that negative genetic effects of recent habitat fragmentation, which so far rather were expected in plants with frequent sexual reproduction, are more severe and more common than previously acknowledged.     

Effects of physiological integration on defense strategies against herbivory by the clonal plant Alternanthera philoxeroides

Aims The plant–herbivore interaction is one of the most fundamental interactions in nature. Plants are sessile organisms, and consequently rely on particular strategies to avoid or reduce the negative impact of herbivory. Here, we aimed to determine the defense strategies against insect herbivores in the creeping invasive plantAlternanthera philoxeroides.     

两种践踏胁迫下克隆整合对入侵植物空心莲子草生长的影响

研究了两种践踏胁迫下克隆整合对入侵植物空心莲子草生长的影响.结果表明:(1)切断分株间的匍匐茎连接,会降低先端分株的生物量、分株数、总匍匐茎长度和总叶片数,但会显著增强基端分株的生物量.(2)对先端分株的践踏胁迫会显著降低先端分株叶片的叶绿素相对含量,对基端分株的践踏胁迫会显著降低基端分株的生物量和总匍匐茎长度.(3)对于基端分株的分株数、总匍匐茎长度和总叶片数来说,当进行基端分株践踏胁迫时,匍匐茎连接对其影响不大,而当进行先端分株践踏胁迫时,则明显对其不利.(4)对于整个克隆片段,践踏胁迫的差异和匍匐茎是否切断对其生长没有显著影响.     

Similarity in the effects of different seed cryoconservation conditions on plant growth and development

Morphological traits of 35 wild plant species were studied after freezing the seeds using quick or programmed two-stage freezing to ?196°C and nondeep freezing to ?10°C. The seeds were stored frozen for 1 month. The seeds of all studied species had low moisture content. Field and laboratory germination rates, leaf growth, the number and length of shoots, the number of generative organs, and variation of all these traits were studied. It was demonstrated that the traits changed in the same directions independently of the freezing conditions, except for laboratory germination rate for some species. The changes were determined by the species-specific plant characteristics rather than by the freezing mode.     

Evidence for the presence of plant growth regulators in commercial seaweed products

Although seaweeds and various seaweed products have been utilized in agricultural practices for many years, the precise mechanism by which they elicit their beneficial growth responses is still not fully understood. The amount of mineral nutrients in commercial preparations cannot account for the magnitude of the responses. Some other factor, such as the presence of endogenous plant growth regulators is, therefore, thought to be involved. This paper reviews the literature supporting evidence for the occurrence of plant hormones in commercial seaweed preparations.abbreviations SWC seaweed concentrate - PGR plant growth regulator - GC-MS gas chromatography/mass spectrometry - ¹H-NMR proton nuclear magnetic resonance - HPLC high performance liquid chromatography     

Effects of salinity and clonal integration on the amphibiousplant Paspalum paspaloides: growth,photosynthesis and tissue ion regulation

Aims Clonal integration can increase performance of clonal plants suffering from environmental stress, and clonal plants in many wetlands commonly face stress of flooding accompanied by salinity. However, few studies have tested roles of clonal integration in amphibious plants expanding from terrestrial to aquatic saline habitats.     

莲草直胸跳甲取食对空心莲子草和莲子草克隆整合的影响

很多外来入侵植物都具有克隆生长习性,探究克隆整合特性与外来克隆植物入侵性间的关系对阐明其生态适应性及入侵机制具有重要的意义。本研究以入侵植物空心莲子草及其本地同属种莲子草为研究对象,比较在生防昆虫莲草直胸跳甲的取食下,克隆整合对两种植物先端分株、基端分株及整个克隆片段生长和生物量分配的影响。结果表明: 在莲草直胸跳甲取食下,有克隆整合的空心莲子草先端分株的叶片数、茎长、分株数及整个克隆片段的地径均显著高于无克隆整合植株,其基端分株及整个克隆片段的地下生物量和总生物量相较于无克隆整合植株分别降低了78.2%、60.9%和48.7%、37.2%;有克隆整合的莲子草先端分株的地径及整个克隆片段的叶片数与无克隆整合植株相比显著增加,其基端分株数显著降低了21.7%,而其先端分株、基端分株及整个克隆片段的生物量均无显著差异。耗益分析表明,在莲草直胸跳甲取食下,空心莲子草先端分株的分株数与生物量及莲子草先端分株的分株数均能通过克隆整合显著受益,而两种植物基端的分株数、生物量的耗益则不受克隆整合处理的影响。这些结果表明,克隆整合虽能在一定程度缓解莲草直胸跳甲对于两种植物先端分株的取食压力,且空心莲子草的克隆整合作用要强于莲子草,但在整个克隆片段水平上,两种植物并不能通过克隆整合显著获益。     

Effects of clonal integration on allelopathy of invasive plant Wedelia trilobata under heterogeneous light conditions

异质光照条件下克隆整合对入侵植物南美蟛蜞菊化感作用的影响 植物入侵已成为全球生态系统最严重的威胁之一。当具有克隆生长能力的入侵植物入侵或定殖到新的生境时,它们相互连接的分株可能受到异质光照的影响。在异质光照条件下,克隆整合对入侵植物化感作用的影响尚不清楚。为研究异质光照条件下克隆整合对入侵植物南美蟛蜞菊(Wedelia trilobata) 化感作用的影响,采用两个连续分株的克隆片段进行了盆栽试验。较老的分株暴露在全光下,而年轻的分株则受到20%的全光照。同时,每个克隆片段的年轻分株与目标植株(一个番茄苗)在盆栽中相邻生长。南美蟛蜞菊的两个连续分株之间的匍匐茎设置切断和不切断两种处理。另外,两株番茄幼苗 (一株作为目标植株)在盆栽中相邻生长作为对照。研究结果表明,当与目标植物相邻生长的南美蟛蜞菊分株之间的匍匐茎保持完整时,目标植株的生物量积累、叶片叶绿素和氮含量、叶绿素荧光参数和净光合速率及其根长和活性相较于匍匐茎切断处理显著降低。异质光照条件下连续两个分株之间碳水化合物的运输或共享可以增强20%全光处理下年轻分株的化感作用。克隆整合在异质光照条件下对具有克隆生长能力的入侵植物的入侵或定殖具有重要意义。     

Effects of clonal integration,nutrients and cadmium on growth of the aquatic macrophyte Pistia stratiotes

许多湿地同时遭受养分和有毒金属的污染,其植被多数为克隆植物。我们假设,富养化和克隆整合可以通过增加植物的生长来提高对有毒金属污染的植物修复能力,即使在毒性胁迫环境下也是如此。为验证此假说,我们将常见、广布的匍匐茎漂浮植物大薸(Pistia stratiotes L.)的单个分株种植在两种不同的养分条件下和两种镉污染处理(无镉或含0.6 mg L⁻¹ 的镉)中42天。通过保持或切断母株与其后代分株之间的连接来维持或阻止克隆整合,并通过保留或移除切断后的后代分株来控制克隆内竞争的有无。由于高养分条件下克隆后代分株的数量增加了一倍,因此镉处理下大薸的生物量在高养分条件下几乎是在低养分条件下的两倍。切断匍匐茎连接对整个克隆(母株和后代分株的总和)的生物量没有影响。切断连接后去除后代分株对镉污染下母株的生物量没有显著的影响,但却显著增加了无镉污染下母株的生物量。这些研究结果支持富养化可以提高水生植物对有毒金属污染的修复能力这一假说,但并不支持克隆整合有利于植物修复的假说。因此,水生植物(如大薸)可能有助于对同时遭受有毒金属和养分污染的湿地进行修复,但克隆片段化对植物的这种修复能力可能没有显著影响。     

Spatial models of foraging in clonal plant species

Ramets of some clonal plant species alter their internode lengths or their frequency of lateral branching in response to their immediate microenvironment. Such “plant foraging” responses are thought to allow clones to concentrate in favorable portions of their environment. Despite widespread interest among ecologists in plant foraging, few realistic models have been developed to examine conditions under which plant foraging responses are likely to provide clones with ecological benefit. In this paper, we develop spatially explicit, stochastic simulation models to examine consequences of both empirical and hypothetical plant foraging responses. We construct a hierarchical series of models in which we incorporate effects of resource heterogeneity on spacer lengths, angles of growth, and lateral branch production. We also vary the number, size, and arrangement of patches, and the presence or absence of ramet mortality. Simulations based on hypothetical data demonstrated the potential importance of shortening spacer lengths in favorable habitat. In these simulations, ramet crowding increased significantly, implying a potential cost to plant foraging responses whose magnitude is large enough to cause ramets to concentrate in favorable patches. Models calibrated with empirical data suggest that when clonal plants were able to concentrate in favorable habitat, this was usually caused by increased daughter ramet production in the favorable habitat. Variation in clonal growth angles had little impact on the ability of ramets or clones to locate favorable patches, but did increase the ability of clones to remain in favorable patches once found. Alterations in the number and size of patches strongly influenced the effectiveness of the foraging response. The spatial arrangement of patches also was important: clumped distributions of patches decreased the success with which plants located favorable patches, especially at the genet level and when the number of patches was low. Finally, when ramet mortality varied with patch quality, there was an increase in the percentage of ramets located in favorable patches; differential ramet mortality also lessened the impact of other effects, such as the decreased success of clones when patches are clumped. Overall, our models indicate that the effectiveness of plant foraging responses is variable and is likely to depend on a suite of environmental conditions.     

Effect of plant growth regulators on in vitro fiber development from unfertilized and fertilized Egyptian cotton ovules

Unfertilized and fertilized ovules of Gossypium barbadense Giza 45 (extra long staple variety) were used to study the effect of plant growth substances (auxins, gibberellins and cytokinins) on in vitro fiber initiation and development. Kinetin, alone did not increase total fiber unit (TFU) of unfertilized ovules, while an increase in TFU value occurred when a constant level of IAA and GA₃ were used either separately or in combination in the liquid medium. GA₃ used alone, produced a higher TFU value than that produced by IAA, whilst, IAA with a constant level of GA₃ (5 M) produced the highest value of TFU. GA₃ with a constant level of IAA (5 M) produced a lower TFU value. Kinetin reduced the stimulatory effect of IAA and GA₃ on TFU value when used in combination with either substance. In fertilized ovules, the highest level of TFU was reached when IAA, with a constant level of GA₃, was added to the medium, whilst its lowest level was obtained when IAA was used alone. Estimation of in vitro fiber production, as well as the effect of growth substances used in different concentrations on in vitro fiber initiation and development from unfertilized and fertilized ovules of Egyptian cotton varieties Gossypium barbadense Giza 45 are discussed.     

植物生长调节剂对银柴胡细胞生长特性的影响

利用细胞悬浮培养技术,研究不同激素对银柴胡细胞生长特性及过氧化氢酶和硝酸还原酶活性的影响。结果表明,第4种激素配比的培养液M₄(MS+6-BA 1.0 mg·L^-1+2,4-D 1.0 mg·L^-1+NAA 1.0 mg·L^-1)的细胞鲜重、干重,细胞数目均明显高于其他处理;M₄处理可有效增强银柴胡细胞硝酸还原酶的活性,提高氮素利用率;M₂(MS+6-BA 1.0mg·L^-1+NAA0.5 mg·L^-1)处理有利于增强银柴胡细胞过氧化氢酶活性。     

No consistent legacy effects of invasion by giant goldenrod (Solidago gigantea) via soil biota on native plant growth

Aims Changes in soil microbial communities after occupation by invasive alien plants can represent legacy effects of invasion that may limit recolonization and establishment of native plant species in soils previously occupied by the invader. In this study, for three sites in southern Germany, we investigated whether invasion by giant goldenrod (Solidago gigantea) leads to changes in soil biota that result in reduced growth of native plants compared with neighbouring uninvaded soils.Methods We grew four native plant species as a community and treated those plants with soil solutions from invaded or uninvaded soils that were sterilized, or live, with live solutions containing different fractions of the soil biota using a decreasing sieve mesh-size approach. We measured aboveground biomass of the plants in the communities after a 10-week growth period.Main Findings Across all three sites and regardless of invasion, communities treated with <20 μm soil biota or sterilized soil solutions had significantly greater biomass than communities treated with the complete soil biota solution. This indicates that soil biota>20 μm are more pathogenic to the native plants than smaller organisms in these soils. Across all three sites, there was only a non-significant tendency for the native community biomass to differ among soil solution types, depending on whether or not the soil was invaded. Only one site showed significant differences in community biomass among soil solution types, depending on whether or not the soil was invaded; community biomass was significantly lower when treated with the complete soil biota solution than with soil biota <20 μm or sterilized soil solutions, but only for the invaded soil. Our findings suggest that efforts to restore native communities on soils previously invaded by Solidago gigantea are unlikely to be hindered by changes in soil microbial community composition as a result of previous invasion.     

Importance of clonal plants and plant species diversity in the Northeast China Transect

In plant communities, the internal (genet-level) control mechanisms on a spatio-temporal scale of clonal plants impose strong constraints on spatial pattern as well as on competitive relations and, thus, species coexistence. Therefore, the presence of clonal species within a plant community affects spatio-temporal dynamics and plant species diversity. We examined the distribution of plants with different clonal growth forms in the Northeast China Transect (NECT) and correlated plant species diversity with the importance of clonal plants, and the importance of phalanx and guerilla clonal plants. Phalanx clonal plants were more abundant in western communities where the altitude was higher and both the soil nitrogen contents and precipitation were relatively low. Whereas guerilla clonal plants were more abundant in the middle of the NECT where the precipitation, mean annual temperature and photosynthetically active radiation were relatively high. In the relatively productive temperate typical steppe, plant species diversity was negatively correlated with the importance of phalanx clonal plants and positively correlated with the importance of guerilla clonal plants. In relatively unproductive temperate desert steppe, plant species diversity was positively correlated with the importance of both phalanx and guerilla clonal plants.     

植物氮形态利用策略及对外来植物入侵性的影响

氮是影响外来植物入侵性的重要因素之一, 但相关研究多关注土壤氮水平的效应, 较少考虑氮形态的作用。为从土壤氮形态利用的角度阐释外来植物的入侵机制, 本文在植物氮形态利用策略分析的基础上, 综述了外来植物氮形态利用的偏好性及其对入侵性的影响。植物的氮形态利用策略有偏好性和可塑性两种, 这可能与植物对土壤氮形态特性的长期适应有关; 植物不仅可以对土壤氮形态做出响应, 而且还能改造土壤氮形态, 并对改变后的土壤氮形态做出反馈响应。很多外来植物入侵硝态氮占优势的干扰生境, 偏好硝态氮的外来植物与本地植物竞争硝态氮; 而偏好铵态氮的外来植物通过抑制土壤硝化作用, 营造铵态氮环境, 促进自身生长, 同时抑制偏好硝态氮的本地植物生长。然而, 植物氮形态利用策略不是一成不变的, 而是受多种生物和非生物因素共同作用影响的复杂过程, 今后应加强多因素交互作用对外来入侵植物氮形态利用策略的影响及机制研究, 更好地揭示氮形态利用策略, 尤其是氮形态利用的可塑性与外来植物入侵性的关系。