Clonal Fragments Research Articles

Developmentally-programmed division of labour in the clonal invader Carpobrotus edulis

Invasive species are one of the main causes for the loss of global biodiversity. However, the mechanisms that explain the success of invasive species remain unsolved. Clonal growth has been pointed out as an attribute that could contribute to the invasiveness of plants, however little research has been conducted to determine the importance of clonal traits in successful invaders. One of the most interesting attributes related to clonal growth is the capacity for division of labour. In this experiment we investigated the capacity for division of labour in the aggressive invader Carpobrotus edulis, and how clonal integration can contribute to the expansion of this species. Division of labour was determined by studying the degree of morphological and physiological specialization of individual ramets to a specific activity: acquisition of soil or aboveground resources and aboveground expansion. Our results showed that there is division of labour in the clonal fragments, with older ramets increasing the biomass allocated to roots (specialization in the uptake of belowground resources) and younger ramets increasing the chlorophyll content and aboveground biomass (specialization in the uptake of aboveground resources). Physiological integration allows division of labour, and as consequence the overall performance of the clonal fragment was enhanced, with connected clonal fragments showing a higher total biomass than severed clonal fragments. Division of labour increased the aboveground growth of apical ramets of C. edulis, and therefore could contribute to an effective colonization of the surrounding area by this aggressive invader. Our study is the first exploring the role of division of labour in the expansion of an invader, and supports the idea that clonal traits could increase the invasiveness of plant species.

异质性光照下匍匐茎草本狗牙根克隆整合的耗益

In a pot experiment,the clonal ramets of Cynodon dactylon,the stolon herbaceous plant,were treated with heterogeneous lighting. Shade stress was carried out on the distal ramets( younger ramets) to three different degrees,and the stolons between the proximal ramets and distal ramets of each pair were treated in an intact or severed manner. The results show that in moderate shade stress,the stolons severed significantly decreased the biomass and net photosynthetic rate( Pn) of distal ramets,and that in serious shade stress,the stolons severed significantly reduced the number of ramets,the number of leaves,biomass,net photosynthetic rate( Pn),the maximal quantm yield of the photosystemⅡ( Fv / Fm)and the effective quantum yield of PSⅡ( ФPSⅡ) of the distal ramets,and that clonal integration alleviated the negative effects of shade stress on the growth of distal ramets. In moderate shade stress,the stolons being intact significantly increased the net photosynthetic rate( Pn) of proximal ramets. In the serious shade stress,the stolons being intact effectively improved the maximal quantm yield of the photosystem Ⅱ( Fv / Fm) and the effective quantum yield of PS Ⅱ( ФPSⅡ) of the proximal ramets. Thus,clonal integration drove the photosynthetic rate of the unstressed proximal ramets to compensatory increase. In contrast to the treatment of the stolons severed,clonal integration would significantly reduce the biomass of the unstressed ramets,but result in no significant change of the whole clonal fragments when the distal ramets were treated with serious shade stress. Therefore,when the distal ramets suffer from serious shade stress,Cynodon dactylon,the stolon herbaceous plant,may take a risk-spreading strategy to reduce the death of genets,which is of vital importance to maintain the fitness of the genets of clonal plants in heterogeneous environments.

Effects of fragmentation on the survival and growth of the invasive, clonal plant Alternanthera philoxeroides

The capacity of small clonal fragments to survive and grow is a major factor in the spread of clonal plants, especially aquatic species. This study of the introduced, invasive, amphibious, stoloniferous herb Alternanthera philoxeroides in China tested the effects of fragment size, of loss of the stolon apex, and of the original position of a fragment within a clone before fragmentation on the survival and growth of fragments in a greenhouse experiment. The stolon internodes of plants consisting of one stolon with 5 ramets were severed in all 16 possible patterns, generating fragments of 1–5 ramets. These 16 fragmentation treatments were crossed with removal of the stolon apex. Fragmentation and apex removal did not affect total growth of plants, but more highly fragmented plants produced smaller, more numerous ramets. The survival of fragments consisting of one original ramet was about 85%, compared to 100% survival of fragments with 5 original ramets. Fragments consisting of the youngest ramets along the original stolon grew more than fragments of the same size that consisted of older ramets. These effects of fragmentation on growth provide new evidence for clonal integration of the rate at which connected ramets produce new ramets and novel evidence that fragments produced from different portions of clones have different potential for spread. They further suggest that detachment of small groups of distal ramets along stolons in the field might be very effective in spreading the species and that a trade-off between the number and the size of new ramets produced by fragments may represent an adaptive, plastic response to disturbance. Results do not recommend intentional fragmentation of clones as a means of controlling the rate of growth of this invasive species but suggest that incidental fragmentation may not increase its growth in mass, although it may increase its rate of spread.

The effects of rooting frequency and position of rooted ramets on plasticity and yield in a clonal species: an experimental study with Glechoma hederacea

AbstractClonal plants produce numerous ramets that can be distributed over a considerable area. Resources are translocated between ramets, especially when they occupy microsites of different quality, or places where leaves or roots cannot be deployed. It is common for a proportion of the ramets of clones and clonal fragments to lack roots. We conducted a greenhouse study using clonal fragments of Glechoma hederacea to examine the effects of differences in the number and position of rooted ramets on yield and plasticity of clonal fragments. We hypothesized that (1) mass of roots and root mass ratio would increase as the number of rooted ramets decreased, (2) plasticity in rooted ramets would buffer the clonal fragment against reduction in yield as the number of rooted ramets declined, (3) ramet plasticity in response to the absence of rooting, and the beneficial effects of this plasticity, would be greater when older ramets were rooted. The same yield was achieved in clonal fragments with only one out of four ramets rooted as in clonal fragments with all four of their ramets rooted, regardless of whether rooting was confined to older or younger ramets. Plasticity in biomass allocated to roots was greater in older rooted ramets succeeded by unrooted ramets than in younger rooted ramets preceded by unrooted ramets. Modular plasticity, involving both direct responses to local conditions, and indirect responses to the conditions experienced by connected modules, buffered performance against variation in rooting ability, enabling clonal fragments to maintain their yield and lateral expansion even when a high proportion of their ramets lacked roots.

Burial depth and stolon internode length independently affect survival of small clonal fragments.

Disturbance can fragment plant clones into different sizes and unstabilize soils to different degrees, so that clonal fragments of different sizes can be buried in soils at different depths. As a short-term storage organ, solon internode may help fragmented clones of stoloniferous plants to withstand deeper burial in soils. We address (1) whether burial in soils decreases survival and growth of small clonal fragments, and (2) whether increasing internode length increases survival and growth of small fragments under burial. We conducted an experiment with the stoloniferous, invasive herb Alternanthera philoxeroides, in which single-node fragments with stolon internode of 0, 2, 4 and 8 cm were buried in soils at 0, 2, 4 and 8 cm depth, respectively. Increasing burial depth significantly reduced survival of the A. philoxeroides plants and increased root to shoot ratio and total stolon length, but did not change growth measures. Increasing internode length significantly increased survival and growth measures, but there was no interaction effect with burial depth on any traits measured. These results indicate that reserves stored in stolon internodes can contribute to the fitness of the A. philoxeroides plants subject to disturbance. Although burial reduced the regeneration capacity of the A. philoxeroides plants, the species may maintain the fitness by changing biomass allocation and stolon length once it survived the burial. Such responses may play an important role for A. philoxeroides in establishment and invasiveness in frequently disturbed habitats.

Physical connection decreases benefits of clonal integration in Alternanthera philoxeroides under three warming scenarios

Physical connection between ramets usually allows clonal plants to perform better but can have the opposite effects in some cases. Clonal integration and the effects of climate warming have been extensively studied, but to date little is known about how climate warming affects the benefits of clonal integration. We conducted a field experiment in which Alternanthera philoxeroides segments with connected and severed stolons were subject to four climate regimes (ambient, day warming, night warming and daily warming), and measured final biomass, number of ramets and total length of stolons. Across the three warming treatments, temperature rise suppressed growth of clonal fragments with connected stolons but increased growth of fragments with severed stolons; temperature rise affected the biomass of distal ramets but not proximal ramets, and had similar effects on the numbers of proximal and distal ramets. When the three warming treatments were considered separately, they had contrasting consequences for the benefits of clonal integration. Specifically, when fragments were exposed to day and night warming, physical connection evened out the advantages of clonal integration that occur under ambient conditions; when fragments were exposed to daily warming, physical connection led to smaller clonal plants. These findings suggest that physical connection between ramets may be disadvantageous to overall performance of A.philoxeroides fragments under climate warming, and also indicate that the net consequences of daily warming outweigh those of day or night warming.

Effects of stolon severing on the expansion ofAlternanthera philoxeroidesfrom terrestrial to contaminated aquatic habitats

AbstractFew studies have examined the effects of clonal integration (translocation of resources between interconnected ramets) during the expansion of amphibious clonal plants from terrestrial to aquatic habitats. We conducted a greenhouse experiment to simulate the expansion of plants from terrestrial to contaminated aquatic habitats in the amphibious stoloniferous herbAlternanthera philoxeroides(alligator weed). The proximal ramets (i.e. relatively old) of clonal fragments grown in uncontaminated soils were connected to (allowing clonal integration) or disconnected from (preventing clonal integration) distal ramets (i.e. relatively young) grown either in uncontaminated water (control, no CuSO4) or in four copper‐contaminated water treatments containing 31.25, 62.5, 125 and 250 mg/L CuSO4, respectively. When a stolon connection was severed, all distal ramets grown in the contaminated water died. When the stolon connection was intact, however, the survival rate of the distal ramets was 85–100% when they were grown at the three lower levels of contamination and 43.75% at the highest level. Moreover, the survival rate and growth of the distal ramets grown in the three lower levels of contamination treatments did not differ from those in the control (uncontaminated water). These results suggest that clonal integration could greatly improve the survival and growth of alligator weed subjected to moderate levels of copper stress. Although clonal integration could also increase the survival rate of the connected distal ramets subjected to the highest level of copper stress (250 mg/L CuSO4) compared with that of disconnected distal ramets, the survival rate and growth measures were still significantly lower than those in the control. This suggests that clonal integration plays a limited role in the survival and growth of alligator weed when it is subjected to severe stress by high levels of copper contamination.

Physiological integration helps a clonal macrophyte spread into competitive environments and coexist with other species

Physiological integration may help clonal macrophytes invade or escape from existing communities. No studies have tested the above hypothesis in aquatic plants. In an outdoor pond experiment, we subjected clonal fragments of the submerged macrophyte Vallisneria spiralis L. to heterogeneous environments in which V. spiralis spread from bare habitats towards vegetated habitats occupied by Myriophyllum spicatum L. or V. spiralis spread from vegetated habitats towards bare habitats. V. spiralis stolons between ramets in bare habitats and in vegetated habitats were either intact or severed. We investigated the habitat selection of V. spiralis by examining the allocation of biomass and ramets to heterogeneous habitats during its vegetative spread phase. Results showed that the stolon connection had different effects on the habitat selection of V. spiralis with regard to invasion and escape. When V. spiralis spread from bare to vegetated habitats, in comparison to severing the stolon, the stolon connection eventually facilitated a 49% increase in biomass and a 27% increase in number of ramets allocated to vegetated habitats. However, when V. spiralis spread from vegetated to bare habitats, biomass and ramets allocated to bare habitats were not significantly changed by the stolon connection (only a 5% increase in biomass and a 6% increase in number of ramets). These results indicate that clonal integration facilitated V. spiralis not to escape from but invade into vegetated habitats. The study provides evidence that physiological integration is important for survival and tolerance of ramets in competitively stressful environments and can help clonal macrophytes coexist with other species.

Salinity stress modulates habitat selection in the clonal plant Aeluropus sinensis subjected to crude oil deposition1,2

Environmental stresses and disturbances are common in terrestrial ecosystems. Clonal integration and foraging behavior are often, but not always, beneficial for clonal plants grown in heterogeneous stressful environments. In this study, clonal fragments of the clonal perennial herb, Aeluropus sinensis (Debeaux) Tzvel (Poaceae), were grown with stolons connected or severed at five salinity levels (0, 50, 100, 200, and 400 mmol L−1 NaCl). In each clonal fragment, the apical ramet was exposed to crude oil on the sediment surface while the basal ramet was not. We proposed three possible scenarios: growth of the apical ramet subjected to crude oil would be (1) enhanced, (2) limited, or (3) not affected by clonal integration. Results supported scenario (2). Responses to crude oil differed between plants grown at low and high salinity levels. For A. sinensis, at high salinity levels, clonal integration promoted habitat selection by decreasing biomass of apical parts to escape the oil polluted habitats and increasing clonal growth of basal parts to select the unpolluted habitats, while at low salinity levels, connection did not influence growth of the basal or apical parts. Salinity modulates the behavior of a clonal plant subjected to heterogeneous crude oil contamination, at least in A. sinensis.

Phenotypic plasticity in response to soil moisture availability in the clonal plant <I>Eremosparton songoricum</I> (Litv.) Vass.

Eremosparton songoricum (Litv.) Vass is a dwarf clonal shrubby legume developed on the windward slopes of mobile or semi-fixed sand dunes of Central Asia. It is assumed that E. songoricum must possess a high degree of phenotypic plasticity for such a heterogeneous habitat. The variations of E. songoricum plants growing in two typical microhabitats (the upper slope and the lower slope of semi-mobile dune) were investigated. The morphological characteristics and the biomass allocation patterns were measured and compared at the clonal fragment level. Compared with the clonal fragment on the lower slope of dune, the clonal fragment on the upper slope of the dune (a) declined in total biomass and ramet height, (b) increased the length of rhizomes and the number of roots, (c) increased the degree of asym- metry, and (d) heightened allocation to the belowground biomass. Our results confirmed the hypothesis of high phenotypic adjustment capacity of E. songoricum to habitat moisture availability. Phenotypic plasticity of E. songoricum contributed to reduce the damage risk, led to an environmentally induced specialization in function of resources exploitation, resulted in its persistence in heterogeneous environments and was adaptive in sand dune environment.

Spatial patterns in defoliation and the expression of clonal traits in grazed meadows

Clonal plant species dominate meadow vegetation where grazing can generate spatial heterogeneity at different scales and can select for species that express particular sets of clonal traits. This in situ study aimed to characterize fine-grained spatial patterns of defoliation (<1 m) induced by contrasting cattle grazing intensities and to link these spatial patterns with the abundance of species-specific clonal traits. Using correlogams and synthetic spatio-temporal indices, the heterogeneity of vegetation height and leaf damage was monitored along a cattle grazing gradient. Species were identified and their clonal traits retrieved from the database CLO-PLA3. Under moderate grazing, fine-grained spatial patterns of defoliation were not stable over time. Defoliation was heterogeneous during the first months of the grazing season and then became homogeneous. Intensive grazing generated homogeneous defoliation, regardless of the date. In the study meadow, grazing gave rise to communities containing a greater abundance of annual species. However, clonal traits assumed to enable clonal fragments to benefit from heterogeneity do not seem advantageous. Increasing grazing intensity promoted species with clonal traits expected to minimize costs associated with clonality (aboveground clonal growth forms, short-distance lateral spread, and (or) short-lived connections). Ungrazed conditions favoured species with clonal traits associated with a high competitive ability.

Effects of Orientation on Survival and Growth of Small Fragments of the Invasive, Clonal Plant Alternanthera philoxeroides

BackgroundThe ability of small clonal fragments to establish and grow after disturbance is an important ecological advantage of clonal growth in plants and a major factor in the invasiveness of some introduced, clonal species. We hypothesized that orientation in the horizontal position (typical for stoloniferous plants) can increase the survival and growth of dispersed clonal fragments, and that this effect of orientation can be stronger when fragments are smaller and thus have fewer reserves to support initial growth.Methodology/Principal FindingsTo test these hypotheses, we compared performance of single-node pieces of stolon fragments of Alternanthera philoxeroides planted at angles of 0, 45 or 90° away from the horizontal position, with either the distal or the proximal end of the fragment up and with either 1 or 3 cm of stolon left attached both distal and proximal to the ramet. As expected, survival and growth were greatest when fragments were positioned horizontally. Contrary to expectations, some of these effects of orientation were stronger when attached stolons were longer. Orientation had smaller effects than stolon length on the performance of fragments; survival of fragments was about 60% with shorter stolons and 90% with longer stolons.Conclusions/SignificanceResults supported the hypothesis that orientation can affect establishment of small clonal fragments, suggested that effects of orientation can be stronger in larger rather than smaller fragments, and indicated that orientation may have less effect on establishment than amount of stored resources.

Favorable fragmentation: river reservoirs can impede downstream expansion of riparian weeds

River valleys represent biologically rich corridors characterized by natural disturbances that create moist and barren sites suitable for colonization by native riparian plants, and also by weeds. Dams and reservoirs interrupt the longitudinal corridors and we hypothesized that this could restrict downstream weed expansion. To consider this "reservoir impediment" hypothesis we assessed the occurrences and abundances of weeds along a 315-km river valley corridor that commenced with an unimpounded reach of the Snake River and extended through Brownlee, Oxbow, and Hells Canyon reservoirs and dams, and downstream along the Snake River. Sampling along 206 belt transects with 3610 quadrats revealed 16 noxious and four invasive weed species. Ten weeds were upland plants, with Canada thistle (Cirsium arvense) restricted to the upstream reaches, where field morning glory (Convolvulus arvensis) was also more common. In contrast, St. John's wort (Hypericum perforatum) was more abundant below the dams, and medusahead wildrye (Taeniatherum caput-medusae) occurred primarily along the reservoirs. All seven riparian species were abundant in the upstream zones but sparse or absent below the dams. This pattern was observed for the facultative riparian species, poison hemlock (Conium maculatum) and perennial pepperweed (Lepidium latifolium), the obligate riparian, yellow nut sedge (Cyperus esculentus), the invasive perennial, reed canary grass (Phalaris arundinacea), and three invasive riparian trees, Russian olive (Elaeagnus angustifolia), false indigo (Amorpha fruticosa), and tamarisk (Tamarix spp.). The hydrophyte purple loosestrife (Lythrum salicaria) was also restricted to the upstream zone. These longitudinal patterns indicate that the reservoirs have impeded the downstream expansion of riparian weeds, and this may especially result from the repetitive draw-down and refilling of Brownlee Reservoir that imposes a lethal combination of drought and flood stress. The dams and reservoirs may also interrupt hydrochory, the downstream flow of seeds and clonal fragments. We thus conclude that with some operational patterns, dams and reservoirs can impede the downstream expansion of riparian weeds.

Do spatial patterns of clonal fragments and architectural responses to defoliation depend on the structural blue-print? An experimental test with two rhizomatous Cyperaceae

Clonal architecture is involved in performance of clonal fragments, as it determines spatial distribution of ramets. It is expected to rely on the species-specific expression of several architectural traits (structural blue-print). However, in contrasting environments, realized clonal architectures may differ, due to phenotypic plasticity. In this paper, we compared clonal architectures between two rhizomatous ecologically close Cyperaceae (Carex divisa and Eleocharis palustris) in non-defoliated and defoliated conditions. Two questions were addressed. (1) How much do the structural blue-print and resulting colonization and occupation of space differ between both species? (2) Does the structural blue-print constrain plastic responses of clonal architecture to defoliation? Traits related to performance, spatial pattern, architecture and biomass allocation of clonal fragments were monitored through an original non-destructive mapping method. In non-defoliated conditions, both species showed similar biomass but contrasting architectures and patterns of biomass allocation to rhizomes that resulted in different spatial patterns. The rhizome network of C. divisa, which consisted in only two primary rhizomes but several branches, was involved in resource storage rather than in spatial colonization. Conversely, E. palustris produced on average six primary rhizomes that grew in the whole horizontal plane, maximizing both occupation and colonization of space. These differences in structural constraints coupled with allometric relationships, resulted in differential responses to defoliation. In C. divisa, the costs associated to defoliation caused a decrease in branching, limiting the area occupied and number of ramets produced by clonal fragments, but increasing ramet density. Conversely, the weakly branched rhizome network of E. palustris was not affected by defoliation. Both spatial strategies (consolidation vs. colonization) are likely to provide ecological advantages allowing their coexistence in grazed meadows.

Influence of light and nitrate assimilation on the growth strategy in clonal weed Eichhornia crassipes

We studied as to how the inter-connected modular architecture of clonal Eichhornia crassipes allows nutrient to transfer from established ramets to developing ramets, and nitrate translocation within clonal system and how such a strategy may play an important role in successful establishment and expansion of this clonal plant. Using this stoloniferous E. crassipes as a model, we studied the effects of light and nitrate availability on growth and nitrate assimilation in inter-connected parent and offspring ramets. Our results showed that increase in light and nitrate availability significantly increased growth rate of the whole clonal fragments and reproduction of offspring ramets in E. crassipes. In addition, increases in nitrate reductase (NR) activity and glutamine synthetase (GS) activity were observed in both parent and offspring ramets with increase in light density and nitrate supply. We also found that nitrate translocation is greater in offspring ramets than in parent ramets under abundant light and nitrate environment in this fast-growing clonal plant. Consequently, majority of nitrate assimilation in offspring ramets is beneficial to the growth of whole clonal system, as indicated by a close correlation between nitrate assimilation in offspring ramets and RGR of whole clonal fragments. We strongly contend that nitrate translocation and assimilation within clone system is important for efficient utilization of nitrogen in alien clonal plant E. crassipes during establishment and expansion, and thus for increase in its invasiveness in natural water columns.

Clonal integration improves the tolerance of Carex praeclara to sand burial by compensatory response

A pot experiment was conducted to examine effects of clonal integration on response of rhizomatous sedge Carex praeclara to local sand burial at different depths. In the experiment, we used clonal fragment consisting of four successive ramets. The two proximal ramets (older) and their offspring, referred as the proximal part, remained unburied while the two distal ramets (younger) and their offspring, referred as the distal part, were either unburied (control) or buried by sand at depth of 7, 14 or 21 cm (sand burial treatment). The rhizomatous connection between the proximal and distal parts was either severed or intact. Severing rhizome dramatically decreased survival of the distal part with increasing sand burial depth. Severing rhizome and sand burial had negative effects on plant performance such as biomass accumulation, number of ramets and number of leaves in the distal part. A cost-benefit analysis based on performance measures showed that the proximal part supported its interconnected distal part and did not incur any costs from this resource export. When connected to the distal part subject to sand burial, the photosynthetic efficiency of the proximal part was enhanced with increasing sand burial depth. The results suggest that the compensatory response (such as photosynthetic and photochemical traits) promoted by the mechanism of source-sink feedback regulation might ameliorate negative effects of sand burial on survival and growth of C. praeclara. Clonal integration, which is one of the functionally important consequences of clonal growth, contributes significantly to the species to withstand local sand burial and successfully inhabit in a desertified alpine habitat, Northwest Sichuan plateau, China.

Clonal integration supports the expansion from terrestrial to aquatic environments of the amphibious stoloniferous herb Alternanthera philoxeroides

Effects of clonal integration on land plants have been extensively studied, but little is known about the role in amphibious plants that expand from terrestrial to aquatic conditions. We simulated expansion from terrestrial to aquatic habitats in the amphibious stoloniferous alien invasive alligator weed (Alternanthera philoxeroides) by growing basal ramets of clonal fragments in soils connected (allowing integration) or disconnected (preventing integration) to the apical ramets of the same fragments submerged in water to a depth of 0, 5, 10 or 15 cm. Clonal integration significantly increased growth and clonal reproduction of the apical ramets, but decreased both of these characteristics in basal ramets. Consequently, integration did not affect the performance of whole clonal fragments. We propose that alligator weed possesses a double-edged mechanism during population expansion: apical ramets in aquatic habitats can increase growth through connected basal parts in terrestrial habitats; however, once stolon connections with apical ramets are lost by external disturbance, the basal ramets in terrestrial habitats increase stolon and ramet production for rapid spreading. This may contribute greatly to the invasiveness of alligator weed and also make it very adaptable to habitats with heavy disturbance and/or highly heterogeneous resource supply.

Effects of physiological integration on the survival and growth of ramets and clonal fragments in the seagrass Syringodium filiforme

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 372:97-104 (2008) - DOI: https://doi.org/10.3354/meps07700 Effects of physiological integration on the survival and growth of ramets and clonal fragments in the seagrass Syringodium filiforme Arthur C. Schwarzschild1,*, Joseph C. Zieman2 1Department of Environmental Sciences, University of Virginia, Anheuser-Busch Coastal Research Center, PO Box 55, Cheriton, Virginia 23316, USA 2Department of Environmental Sciences, University of Virginia, PO Box 400123, Charlottesville, Virginia 22904, USA *Email: arthur@virginia.edu ABSTRACT: Mesocosm experiments examined the importance of clonal integration to the growth of Syringodium filiforme ramets (short shoots with their associated section of rhizome and roots) and clonal fragments. High mortality and reduced growth following isolation from parent clones indicated that young ramets are dependent on clonal integration for survival and growth. In contrast, older ramets survived isolation, grew, and branched forming a new rhizome apical meristem (RAM) and additional ramets. Similar results were obtained from an experiment examining the survival and growth of clonal fragments. Older fragments produced longer branches and more new ramets than did younger fragments during the same time period. Cutting the rhizome behind a ramet led to a decrease in ramet growth compared to cutting the rhizome in front of a ramet. These results indicate that S. filiforme RAMs and young ramets act as physiological sinks, drawing resources from and reducing the growth potential of older ramets. These results also suggest that restoration projects should utilize planting units comprised of older clonal fragments due to increased survival and growth potential. Using older portions of clones as planting units negates the need for an intact RAM, as these fragments are capable of producing multiple new growth axes. Finally, our results indicate that in order to gain an accurate picture of seagrass meadow health in disturbance prone environments, rhizome condition and ramet position relative to the RAM should be considered in addition to the standard measurements of ramet productivity. KEY WORDS: Clonal integration · Resource sharing · Ramet growth · Syringodium filiforme · Seagrass Full text in pdf format PreviousNextCite this article as: Schwarzschild AC, Zieman JC (2008) Effects of physiological integration on the survival and growth of ramets and clonal fragments in the seagrass Syringodium filiforme. Mar Ecol Prog Ser 372:97-104. https://doi.org/10.3354/meps07700 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 372. Online publication date: December 09, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Photosynthetic response of Fragaria orientalis in different water contrast clonal integration

AbstractThe capacity to exchange resources and non‐resource agents is one of the most outstanding features of clonal plants. Contrast between patches in a heterogeneous environment is the main external driving force behind integration effects. It was hypothesized, on the basis of the source–sink hypothesis, that assimilate demand from drought‐stressed ramets will result in enhancement of the photosynthesis of well‐watered ramets by a mechanism of feedback regulation, that the negative effect of drought on the photosynthesis of drought‐stressed ramets will be ameliorated by physiological integration, and that these effects will be enhanced by increasing contrast. A pot experiment was conducted with clonal fragments consisting of two interconnected ramets of Fragaria orientalis. In the experiment, both the connected and the disconnected clonal fragments were divided into three water contrast groups: (1) homogeneous (no contrast) group; (2) low‐contrast group; (3) high‐contrast group. The photosynthesis and stress tolerance of drought‐stressed ramets did not decrease under the support of well‐watered ramets when they were connected, allowing clones to maintain their performance in less favorable environments. But the photosynthesis and stress tolerance of drought‐stressed ramets decreased with increasing drought‐stress when stolons were disconnected. With a feedback regulation process, the photosynthesis of well‐watered ramets connected to drought‐stressed ramets was enhanced by the latter, which can compensate, at least partially, for the cost of maintaining the stressed ramets. Drought‐stressed ramets gained more benefits in a high‐contrast environment than in a lower‐contrast environment; this can enhance the survival of drought‐stressed ramets in unfavorable habitats, especially stressed patches that would otherwise be unexploitable by independent ramets. But photosynthesis of well‐watered ramets did not increase with increasing water availability contrast. It can be concluded that photosynthesis and stress tolerance of F. orientalis was affected by clonal integration and by contrasts of water availability.

Clonal growth strategies in simultaneously persistent and expanding Trifolium repens patches

Plants with clonal growth can generate patches dominated by a single species. In time, patches can change and may fragment, form a ring, dissolve or both persist and expand. For patches to maintain their original habitat and simultaneously increase in size, ramets or clonal fragments must both promote local persistence inside the patch and grow out of the patch into new habitats. This study analyses simultaneously expanding and persistent Trifolium patches in a nutrient-poor lawn that is frequently cut, and where the Trifolium is competitively superior to the grass species. Trifolium primary stolon growth strategies were analyzed in relation to their location (border, middle, and center) inside the patch, and according to patch size (small, medium, and large). It was hypothesized that different growth strategies inside a patch can explain both persistent and expanding patch of Trifolium, and that growth strategies were different between patch sizes. Primary Trifolium stolons had two different growth strategies inside and at the border of patches: (i) stolons at the border were long, grew fast, had few lateral stolons, and grew out of the patch, while (ii) stolons inside the patch were smaller, grew slowly, and had more lateral stolons and a wide range of growth directions. Growth strategies were not different between patch sizes. The directional growth and the high growth rate at the border will increase the patch size with time, while the growth strategy near the center consolidates the patch in space and time, by placing ramets inside the patch. Different growth strategies near the center and on the border result in Trifolium patches that are simultaneously persistent and on the increase. The results also indicate a division of labor among primary Trifolium stolons in a patch.