Offspring Ramets Research Articles

Erratum to: Exploitation of patchy soil water resources by the clonal vine Ficus tikoua in karst habitats of southwestern China

The karst habitats of southwestern China are characterized by a highly heterogeneous distribution of water resources. We hypothesized that the clonal integration between connected ramets of the clonal vine Ficus tikoua was an important adaptive strategy to the patchy distribution of water resources in these habitats. We grew ramet pairs (each consisting of a parent and an offspring ramet) in both homogeneously and heterogeneously watered conditions. The offspring ramets were well-watered, whereas their connected parent ramets were randomly assigned to four water treatments: well-watered, mild water stress, moderate water stress, and severe water stress. Increasing water stress decreased leaf water potential, relative water content, net assimilation rate, maximum quantum yield of PSII (F v/F m), and biomass of the parent ramets. Subjecting the parents to water stress significantly increased root biomass and root mass ratio (RMR) of their offspring ramets. Exploitation of plentiful water resources through the increased adventitious roots connected to another soil patch permitted the complete restoration of water relations and photosynthetic capacity of offspring ramets after an initial depression. Water relations and gas exchange of the parents were not affected by the water supply to their connected offspring ramets, suggesting that offspring ramets hardly exported water to the stressed parents. However, net assimilation rate and proline content of the offspring ramets increased when they were connected to water-stressed parents. The compensatory photosynthetic responses of offspring ramets connected to stressed parents revealed an increasing trend as the experiment progressed. Morphological and physiological plasticity of F. tikoua in response to heterogeneous water resources allow them to adapt to karst habitats and be suitable candidates for vegetation restoration projects.

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.

Effects of Elevated CO2 on Growth and Nutrient Uptake of Eichhornia crassipe Under Four Different Nutrient Levels

Although the climate change effects on plants have been a focus for more than two decades, such effects on aquatic species remain largely unknown. To evaluate the potential effects of elevated CO2 on growth and nutrient uptake of Eichhornia crassipe Solms (commonly known as water hyacinth, the world’s most significant invasive aquatic weed), plants were grown at two CO2 concentrations (380 and 800 ppm) combined with four nutrient levels (oligo-, meso-, eu-, and hypertrophic) for 2 months. Overall, elevated CO2 consistently enhanced plant growth at all nutrient levels, indicating more infestations of water hyacinth in future natural eutrophic waters. Moreover, the enhancement extent varied among nutrient availabilities, being more in eu- and hypertrophic levels and less in meso- and oligotrophic levels. Furthermore, the CO2 enrichment-deduced assimilation was allocated more to plant roots than shoots which would improve the nutrient absorption capacity and mostly transferred to offspring ramets rather than maintained at the mother ramet which would benefit the vegetative reproduction. Finally, under elevated CO2, although the nitrogen (N) and phosphorus (P) contents of E. crassipe slightly decreased which might mean increased difficulties in preventing its infestation by reducing N and/or P in eutrophic waters, the total N and P accumulation increased suggesting higher bioremediation efficiency of using water hyacinth for water eutrophication.

Nitrate reduction in ramets of a clonal plant Eichhornia crassipes responding to nitrate availability during clonal growth stage

Effect of nitrate availability on nitrate reduction was examined in inter-connected ramets of invasive clonal plant Eichhornia crassipes grown with two nitrate supply regimes during different clonal growth stage. Increase of nitrate availability accelerated nitrate reductase activity (NRA) in parent and offspring ramets of E. crassipes, and there was greatly different pattern in inter-connected ramets during clonal growth stage. Leaf NRA was lower in offspring than that in parent ramets in phase 1, while significantly higher leaf NRA in offspring ramets was detected during phase 2. The results indicated NRA in inter-connected ramets of E. crassipes was highly dependent on nitrate availability and growth stage.

Ephemeral clonal integration in Calathea marantifolia (Marantaceae): Evidence of diminished integration over time

A major advantage of clonal growth forms is the intergenerational transfer of resources through vascular connections (clonal integration). Connections linking ramets can be persistent or ephemeral. For species with ephemeral connections, whether the extent of clonal integration changes over time is unclear. To address this issue, we tracked water movement using an isotopic label and assessed the demographic performance of parent and offspring ramets over time in a severing experiment. Our study system was the understory herb Calathea marantifolia, which has parent ramets that produce vegetative bulbils (clonal offspring) that pass through distinct pre- and post-rooting stages. Little water was transported between parents and offspring, and the direction of movement was primarily from parent to pre-rooting offspring. Anatomical observations of inter-ramet connections showed that vascular bundles were twice as abundant in parent stems compared to inter-ramet connections. Severing inter-ramet connections reduced the growth of offspring ramets but not parents. Survival of pre-rooting offspring was reduced by 10% due to severing, but post-rooting offspring were not affected. Our results suggest that offspring ramets of C. marantifolia are weaned from their parent as they progress from pre- to post-rooting stages.

Effects of inoculation with native arbuscular mycorrhizal fungi on clonal growth of Potentilla reptans and Fragaria moschata (Rosaceae)

Many clonal plants live in symbiosis with ubiquitous arbuscular mycorrhizal (AM) fungi, however, little is known about their interaction with respect to clonal reproduction and resource acquisition. The effects of arbuscular mycorrhiza on the growth and intraclonal integration between ramets of two stoloniferous species were studied experimentally in a nutritionally homogenous soil environment. Two species coexisting at the same field site, Potentilla reptans and Fragaria moschata, were selected as model plants for the study. Pairs of their ramets were grown in neighbouring pots with each ramet rooted separately. Four inoculation treatments were established: (1) both mother and daughter ramets remained non-inoculated, (2) both ramets were inoculated with a mixture of three native AM fungi from the site of plant origin, (3) only mother or (4) daughter ramet was inoculated. The stolons connecting the ramets were either left intact or were disrupted. Despite the consistent increase in phosphorus concentrations in inoculated plants, a negative growth response of both plant species to inoculation with AM fungi was observed and inoculated ramets produced fewer stolons and fewer offspring ramets and had lower total shoot dry weights as compared to non-inoculated ones. A difference in the extent of the negative mycorrhizal growth response was recorded between mother and daughter ramets of P. reptans, with daughter ramets being more susceptible. Due to AM effect on ramet performance, and thereby on the source-sink relationship, inoculation also significantly influenced biomass allocation within clonal fragments. Physiological integration between mother and daughter ramets was observed when their root systems were heterogeneous in terms of AM colonization. These results hence indicate the potential of mycorrhizal fungi to impact clonal growth traits of stoloniferous plant species, with possible consequences for their population dynamics.

Integration in the clonal plant Eriophorum angustifolium: an experiment with a three-member-clonal system in a patchy environment

A clonal plant in heterogeneous environments is usually expected to profit from resource exchange via a clonal network where ramets placed in contrasting environments can specialise so to acquire the most abundant resources. An experiment was designed using the three member clonal system of Eriophorum angustifolium, which consisted of one parent ramet growing in a resource poor environment and two offspring: one was limited in growth by nutrients while the other was light limited; the contrast in availability of limited resources between the offspring ramets was high, medium or none, with the system either connected or severed. The total resource availability was the same in all treatments. We proposed four possible scenarios for the system: offspring ramets will share resources via the deficient parent ramet, and the whole clone will profit from the contrasting environment (scenario 1); offspring ramets will support exclusively the parent ramet, and the whole clone will profit from a homogeneous environment (scenario 2); offspring ramets will stop the export of the limiting resource to the parent ramet, with split and connected treatments not differing (scenario 3); and offspring ramets will exhaust the carbon stored in the biomass of the parental ramet; offspring ramet will profit from connection (scenario 4). In the experiment, the limiting resources were sent to the strongest sink (scenario 2). The parent ramet growing in a deficient environment received the highest support in the treatment where both offspring ramets were growing in the same conditions (no-contrast treatment). Production of new shoots, but not biomass of whole clone, was supported in a homogenous environment. The experiment revealed that multiple stresses might prohibit free exchange of limiting resources via the clonal network and supports the idea that experimental studies on more complex clones are essential for understanding the costs and benefits of clonal growth.

Clonal splitters and integrators in harsh environments of the Trans-Himalaya

Individuals of clonal plants consist of physically and physiologically connected ramets. In splitters, they are integrated for a time shorter than ramet generation time (i.e. the time it takes to produce the first offspring ramet), whereas in integrators connections between ramets persist for a longer time. It has been predicted that integrators should prevail in stressful environments, such as habitats poor in nutrients, whereas splitters are expected to dominate in benign habitats, such as fertile areas with a moderate climate. I tested these predictions in four dry mountain areas of the Trans-Himalaya, in high altitudes subjected to multiple stresses. In accordance with the expectations I found that clonal plants with integrated ramets reach higher mean and maximum altitudes than splitters. Integrators were over-represented in nutrient-poor habitats, such as dry semi-deserts, sandy steppes and in subnival habitats, whereas splitters preferentially colonised mesic habitats, saline sites and wetlands. While there was no difference in the representation of splitters and integrators in habitats with an unstable surface, such as screes, dunes and water bodies, fully integrated clonal plants preferred very stable environments, such as banks of streams covered by closed-canopy vegetation. Most relationships between clonal integration and environmental factors were explainable by the phylogenetic relationship between the species, only the significant preference of splitters for shaded environments persisted in phylogenetically corrected analysis. The results indicate that clonal integration belongs to a set of evolutionarily conservative plant traits, usually shared by related species. Consequently, the adaptive value of clonal integration in individual habitats remains questionable.

Responses of the clonal Fragaria vesca to microtopographic heterogeneity under different water and light conditions

Vegetative multiplication allows clonal systems to spread horizontally and to establish (descendents) ramets in sites of contrasting resource status. Stolon or rhizome connections between ramets permit the transport of resources within the clone. As a result of such physiological integration, clones can act as cooperative systems, enabling buffering of any differences in resource supply among ramets due to local heterogeneity. This study tests the hypothesis that parent ramets of Fragaria vesca L. enhance their photosynthetic activity when connected to shaded or drought-stressed offspring ramets as result of the assimilate demand from those ramets. The study also investigated the extent to which small-scale topographic heterogeneity (i.e. offspring ramets at higher or lower level than parents) may influence the physiological integration, in terms of photosynthetic efficiencies, biomass and production of new ramets. Results showed that the photosynthetic efficiencies of parent ramets were increased in response to the assimilate demand made by drought-stressed offspring ramets, especially under shade conditions. We attribute this response to a mechanism of feed-back regulation in line with the source–sink hypothesis. We also found that offspring ramets at a raised topographic position with respect to parents showed a significant decline in the production of new ramets and a reduction in total biomass relative to offspring at a lower level or the same level. We conclude that microtopographic aspects of environmental heterogeneity may involve additional costs for ramet establishment of ramets.

Small-scale Heterogeneity in Soil Quality Influences Photosynthetic Efficiency and Habitat Selection in a Clonal Plant

In clonal plants, internode connections allow translocation of photosynthates, water, nutrients and other substances among ramets. Clonal plants form large systems that are likely to experience small-scale spatial heterogeneity. Physiological and morphological responses of Fragaria vesca to small-scale heterogeneity in soil quality were investigated, together with how such heterogeneity influences the placement of ramets. As a result of their own activities plants may modify the suitability of their habitats over time. However, most experiments on habitat selection by clonal plants have not generally considered time as an important variable. In the present study, how the foraging behaviour of clonal plants may change over time was also investigated. In a complex of environments with different heterogeneity, plant performance was determined in terms of biomass, ramet production and photosynthetic activity. To identify habitat selection, the number of ramets produced and patch where they rooted were monitored. Parent ramets in heterogeneous environments showed significantly higher maximum and effective quantum yields of photosystem II than parents in homogeneous environments. Parents in heterogeneous environments also showed significantly higher investment in photosynthetic biomass and stolon/total biomass, produced longer stolons, and had higher mean leaf size than parents in homogeneous environments. Total biomass and number of offspring ramets were similar in both environments. However, plants in homogeneous environments showed random allocation of offspring ramets to surrounding patches, whereas plants in heterogeneous environments showed preferential allocation of offspring to higher-quality patches. The results suggest that F. vesca employs physiological and morphological strategies to enable efficient resource foraging in heterogeneous environments and demonstrate the benefits of physiological integration in terms of photosynthetic efficiency. The findings indicate that short-term responses cannot be directly extrapolated to the longer term principally because preferential colonization of high-quality patches means that these patches eventually show reduced quality. This highlights the importance of considering the time factor in experiments examining responses of clonal plants to heterogeneity.

Habitat selection in spatially heterogeneous environments: a test of foraging behaviour in the clonal submerged macrophyte Vallisneria spiralis

Summary1. To test whether clonal macrophytes can select favourable habitats in heterogeneous environments, clonal fragments of the stoloniferous submerged macrophyte Vallisneria spiralis were subjected to conditions in which light intensity and substratum nutrients were patchily distributed. The allocation of biomass accumulation and ramet production of clones to the different patches was examined.2. The proportion of both biomass and ramet number of clones allocated to rich patches was significantly higher than in poor patches. The greatest values of both clone and leaf biomass were produced in the heterogeneous light treatment, in which clones originally grew from light‐rich to light‐poor patches, while clones produced the most offspring ramets in the treatments with heterogeneous substratum nutrients. Similarly, root biomass had the highest values in nutrient‐rich patches when clones grew from nutrient‐rich to nutrient‐poor patches.3. The quality of patches in which parent ramets established significantly influenced the foraging pattern. When previously established in rich patches, a higher proportion of biomass was allocated to rich patches, whereas a higher proportion of ramet number was allocated to rich patches when previously established in poor patches.4. Results demonstrate that the clonal macrophyte V. spiralis can exhibit foraging in submerged heterogeneous environments: when established under resource‐rich conditions V. spiralis remained in favourable patches, whereas if established in adverse conditions it could escape by allocating more ramets to favourable patches.

Development, photosynthetic activity and habitat selection of the clonal plant Fragaria vesca growing in copper-polluted soil.

The ability of clonal systems to spread by ramet production may expose the clone to spatial heterogeneity. This study explored the physiological and morphological responses in the clonal plant Fragaria vesca L. growing in homogeneous (Cu-contaminated or uncontaminated) or in heterogeneous environments with patches of contrasting quality (Cu-contaminated or uncontaminated). We also investigated the potential of this species to selectively establish ramets within a heterogeneous environment. In heterogeneous environments, plants expanded ramets randomly, but selectively established ramets in the favourable patches. We discuss whether the selective establishment of ramets is a consequence of direct suppression of plant growth due to copper toxicity. The assimilate demand from offspring ramets in unfavourable environments increased the chlorophyll content and photosynthetic efficiency of parents by a feedback regulation process. Integration ameliorated the effects of copper on the photochemical efficiency of the offspring ramets. We did not observe integration costs, in terms of total biomass, for parents supporting ramets in Cu-contaminated environments, although we did detect costs in terms of ramet production. Parents with offspring ramets in Cu-contaminated environments produced 25 times more reproductive biomass than parents with offspring ramets in uncontaminated environments. We interpret this as a strategy for escaping from stressful environments. In this study, we extend the concept of physiological integration in clonal plants to include photochemical responses.

Presence of Developing Ramets of Fragaria vesca L. Increases Photochemical Efficiency in Parent Ramets

Clonal plants may translocate photosynthates, water, and nutrients from established (source) ramets to developing (sink) ramets. The sink/source hypothesis states that photosynthesis may be regulated, at least in part, by the balance between source and sink tissues. We investigated the influence of physiological integration on photosynthetic efficiencies to test predictions based on the sink/source hypothesis that photosynthetic efficiencies in parent ramets may be increased by the assimilate demand made by connected offspring ramets. We grew parent ramets of Fragaria vesca connected to four, one, or no offspring ramets. They were grown in well‐watered or drought‐stress conditions. All parent ramets survived at the end of the experiment, regardless of the number of offspring ramets they supported or the moisture conditions in which these were growing. However, the survivorship of offspring ramets was higher for well‐watered and connected ramets than for drought‐stressed and disconnected ramets. In parent ...

Timing of disturbance changes the balance between growth and survival of parent and offspring ramets in the clonal forest understory herb Uvularia perfoliata

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

Infection of Trientalis europaea by the systemic smut fungus Urocystis trientalis: disease incidence, transmission and effects on performance of host ramets

Summary 1 The effects of fungus infection on a natural population of the pseudoannual plant Trientalis europaea were followed for 4 years. 2 The incidence of the disease was low, showed little temporal variation during the period of study and was not affected by ramet size. Disease reduced flowering, fruiting, stolon length and the number and size of daughter tubers, all of which were positively correlated with ramet size. The year–disease interaction was not significant, except for flowering, suggesting little variation in the aggressiveness of the pathogen. 3 Disease reduced survival of ramets to the end of the growing season, although the effect varied with ramet size, and decreased tuber survival both by reduction of tuber size and by reduction of the overwintering ability of tubers of a given size. 4 For two of the three annual transitions the size of the offspring ramets was affected negatively by infection in the previous year. 5 Disease transmission occurred along the stolons of only 31% of the diseased ramets. The probability of disease being shown in the following year decreased with stolon length. 6 Although disease had a detrimental effect on ramet fitness, the low level of incidence and the stability of the clone dynamics in simulation models suggest only a minor role of the disease in population regulation in this species.

Modeling Investments in Seeds, Clonal Offspring, and Translocation in a Clonal Plant

Clonal plants that can switch facultatively between sexual and asexual reproduction may respond plastically to the environment. We constructed a dynamic state variable model to examine how the measure of fitness, ramet and genet mortality, and the assimilation rates of a parent and its clonal offspring influence behavioral investments in ramet growth, clonal offspring, seeds, and continued resource translocation to clonal offspring after establishment. The model leads to predictions that ramet and genet mortality rates and/or the fitness payoff from producing seeds must be high for seed production to capture a proportion of reproductive investments. If seed production occurs as a result of high ramet or genet mortality rates, then results indicate that it is better to produce seeds early in the season, regardless of ramet size. In contrast, if seed production is favored as a result of its large contribution to fitness, then it is predicted to depend on ramet size more than on time. While the total amount of biomass directed to reproduction is predicted to increase with a ramet’s own productivity, the proportion of this biomass invested clonally or sexually depends on the resource environment encountered by that ramet’s clonal offspring; more productive surroundings favor investment in clonal offspring that forage locally, reduce the risk of genet mortality, and increase the expectation for future seed production by the genet. The model we present also suggests that a higher rate of translocation to support clonal offspring benefits a genet when the parent and offspring ramets have contrasting productivities. In addition, the model also leads to the predictions that translocation is more advantageous when the currency of fitness selects for increases in ramet size more than ramet number and when the probability of mortality is correlated among ramets.

MODELING INVESTMENTS IN SEEDS, CLONAL OFFSPRING, AND TRANSLOCATION IN A CLONAL PLANT

Clonal plants that can switch facultatively between sexual and asexual re- production may respond plastically to the environment. We constructed a dynamic state variable model to examine how the measure of fitness, ramet and genet mortality, and the assimilation rates of a parent and its clonal offspring influence behavioral investments in ramet growth, clonal offspring, seeds, and continued resource translocation to clonal off- spring after establishment. The model leads to predictions that ramet and genet mortality rates and/or the fitness payoff from producing seeds must be high for seed production to capture a proportion of reproductive investments. If seed production occurs as a result of high ramet or genet mortality rates, then results indicate that it is better to produce seeds early in the season, regardless of ramet size. In contrast, if seed production is favored as a result of its large contribution to fitness, then it is predicted to depend on ramet size more than on time. While the total amount of biomass directed to reproduction is predicted to increase with a ramet's own productivity, the proportion of this biomass invested clonally or sexually depends on the resource environment encountered by that ramet's clonal offspring; more productive surroundings favor investment in clonal offspring that forage locally, reduce the risk of genet mortality, and increase the expectation for future seed production by the genet. The model we present also suggests that a higher rate of translocation to support clonal offspring benefits a genet when the parent and offspring ramets have contrasting produc- tivities. In addition, the model also leads to the predictions that translocation is more advantageous when the currency of fitness selects for increases in ramet size more than ramet number and when the probability of mortality is correlated among ramets.

Circular arrangement of Stipagrostis ciliata clumps in the Negev, Israel and near Gokaeb, Namibia

Circles of tufts or tuft remnants of the perennial grass Stipagrostis ciliata were found in sandy soils in desert areas of Israel and Namibia. It is suggested that such a circular pattern is due to vegetative propagation of this and other species by means of horizontal rhizomes. The central part of the older specimens dies and detached offspring ramets develop in the periphery of the genet. Other species with similar arrangement of ramets are Stipagrostis obtusa, Asphodelus ramosus (Litiaceae), and Cyperus macrorrhizus (Cyperaceae). The shrubby dicotyledones Calligonum comosum and Artemisia monosperma, which also produce circles of clumps, are capable of reproducing vegetatively by means of adventive roots and new branches, which are the extension of buried branches in the periphery of the genet.

Advantages of Clonal Growth in Heterogeneous Habitats: An Experiment with Potentilla Simplex

1 The ability to share resources between modules (ramets) is considered to be a benefit of the clonal growth habit. This type of physiological integration may buffer the entire clone against locally adverse conditions resulting from the patchy distribution of resources. The hypothesis that physiological integration is most advantageous in a heterogeneous habitat was tested using the clonal, perennial species Potentilla simplex (Rosaceae). 2 Five artificial habitat types differing in nutrient status were constructed in the glasshouse and the performance of intact and disconnected clones (clones in which all ramets were severed from each other following the establishment of roots) growing in them was compared. The habitat types ranged from homogeneously poor via three levels of spatial heterogeneity in nutrient supply to homogeneously rich. 3 Intact clones growing in the heterogeneous habitats weighed significantly more than their disconnected counterparts, supporting the hypothesis. The benefits of resource sharing were enhanced with increasing patchiness of the habitat. No differences in biomass between intact and disconnected clones appeared in the homogeneous settings. 4 Parent ramets supported their offspring at a large cost in biomass to themselves, but the offspring ramets benefited from clonal integration irrespective of the quality of the patches they occupied. 5 Across all habitats, intact stolons elongated more than the severed ones. This increased mobility of intact clones implies that clonal integration may allow this species to escape from unfavourable patches. The enhanced performance of connected ramets rooted in rich patches shows that clonal integration also enables clones to exploit resource-rich microhabitats, thereby maximising foraging ability and resource acquisition, particularly when resources are distributed in patches. 6 The cumulative effects of parent and offspring biomass and offspring ramet number appear to explain the trend in performance of intact and disconnected clones observed in the homogeneous and heterogeneous habitats.

TRANSPORT OF CARBON AMONG CONNECTED RAMETS OF EICHHORNIA CRASSIPES (PONTEDERIACEAE) AT NORMAL AND HIGH LEVELS OF CO2

The floating, stoloniferous plant, Eichhornia crassipes, has high rates of productivity and rapidly invades new sites. Because the transport of carbon among connected ramets is known to increase the growth of clonal plants, we asked whether there is intraclonal carbon transport in E. crassipes. Because net photosynthesis of E. crassipes is significantly higher at high levels of atmospheric CO2, we also asked if high CO2 can change patterns of carbon transport in ways that might modify clonal growth. We exposed individual ramets within groups of connected ramets to 14CO2 for 15–45 min and measured the distribution of 14C in the group after 4 days of growth at 350, 700, 1,400, or 2,800 μ1 1−‐1 CO2. At 350 μ1 1−‐1 CO2, a parent ramet exported approximately 10% of the 14C that it assimilated to its first rooted offspring ramet. The offspring exported a similar percentage of the l4C it assimilated toward the parent; two‐thirds of this 14C was retained by the parent, and one‐third moved into new offspring of the parent. In all ramets, imported carbon moved into leaves as well as roots. At the higher levels of CO2, the percentage of assimilated carbon exported from a parent ramet to the leaf blades of its first offspring was lower by half. High CO2 had little other effect on carbon transport. E. crassipes maintains bidirectional transport of carbon between ramets even under uniform and favorable environmental conditions and when external CO2 levels are very high.