Resource Translocation Research Articles

Strategies of resource sharing in clonal plants: A conceptual model and an example of contrasting strategies in two closely related species.

Clonal growth is widespread among herbaceous plants, and helps them to cope with environmental heterogeneity through resource integration via connecting clonal organs. Such integration is considered to balance heterogeneity by translocation of resources from rich to poor patches. However, such an 'equalisation' strategy is only one of several possible strategies. Under certain conditions, a strategy emphasising acropetal movement and exploration of new areas or a strategy of accumulating resources in older ramets may be preferred. The optimal strategy may be determined by environmental conditions, such as resource availability and level of light competition. We aimed to summarise possible translocation strategies in a conceptual analysis and to examine translocation in two species from different habitats. Resource translocation was compared between two closely related species from different habitats with contrasting productivity. The study examined the bidirectional translocation of carbon and nitrogen in pairs of mother and daughter ramets grown under light heterogeneity (one ramet shaded) at two developmental stages using stable-isotope labelling. At the early developmental stage, both species translocated resources toward daughters and the translocation was modified by shading. Later, the species of low-productivity habitats, Fragaria viridis, translocated carbon to shaded ramets (both mother and daughter), according to the 'equalisation' strategy. In contrast, the species of high-productivity habitats, Potentilla reptans, did not support shaded mother ramets. Nitrogen translocation remained mainly acropetal in both species. The two studied species exhibited different translocation strategies, which may be linked to the habitat conditions experienced by each species. The results indicate that we need to consider different possible strategies. We emphasise the importance of bidirectional tracing in translocation studies and the need for further studies to investigate the translocation patterns in species from contrasting habitats using a comparative approach.

Fungal organic acid uptake of mineral-derived K is dependent on distance from carbon hotspot.

Fungal species are foundational members of soil ecosystems with vital contributions that support interspecies resource translocation. The minute details of these biogeochemical processes are poorly investigated. Here, we addressed this knowledge gap by probing fungal growth in a novel mineral-doped soil micromodel platform using spatially-resolved imaging methodologies. We found that fungi uptake K from K-rich minerals using organic acids exuded in a distance-dependent manner from a carbon-rich hotspot. While identification of specific mechanisms within soil remains challenging, our findings demonstrate the significance of reduced complexity platforms such as the mineral-doped micromodel in probing biogeochemical processes. These findings provide visualization into hyphal uptake and transport of mineral-derived nutrients in a resource-limited environment.

Root grafts matter for inter-tree water exchange - a quantification of water translocation between root grafted mangrove trees using field data and model based indication.

Trees interconnected through functional root grafts can exchange resources, but the effect of exchange on trees remains under debate. A mechanistic understanding of resources exchange via functional root grafts will help understand their ecological implications for tree water exchange for individual trees, groups of trees, and forest stands. To identify the main patterns qualitatively describing the movement of sap between grafted trees, we reviewed available literature on root grafting in woody plants that focus on tree allometry and resource translocation via root grafts. We then extended the BETTINA model, which simulates mangrove (Avicennia germinans) tree growth on the individual tree scale, in order to synthesize the available empirical information. Using allometric data from a field study in mangrove stands, we simulated potential water exchange and analyzed movement patterns between grafted trees. In the simulations, relative water exchange ranged between -9.17 and 20.3 %, and was driven by gradients of water potential, i.e. differences in tree size and water availability. Moreover, the exchange of water through root grafts alters the water balance of trees and their feedback with the soil: grafted trees that receive water from their neighbors reduce their water uptake. Our individual-tree modelling study is a first theoretical attempt to quantify root graft-mediated water exchange between trees. Our findings indicate that functional root grafts represent a vector of hydraulic redistribution, helping to maintain the water balance of grafted trees. This non-invasive approach can serve as a fundament for designing empirical studies to better understand the role of grafted root interaction networks on a broader scale.

Heat stress effects on the reproductive physiology and yield of wheat

AbstractClimate change is adversely affecting wheat yields as the associated rising temperatures damage its reproductive physiology. Heat stress affects wheat at various stages of growth, but flowering and reproductive phases are the most sensitive to high temperatures as flower opening usually occurs in cooler environments. Heat stress at meiosis causes ovule and pollen sterility along with anther dehiscence. During pollen development, temperatures >30°C cause pollen abortion. At anthesis, heat stress limits resource translocation to developing grain, resulting in small grain and low yields. During grain development, heat stress shortens the grain‐filling duration and decreases starch and protein accumulation due to reduced activity of grain biosynthesis enzymes and impaired flag leaf assimilatory efficiency and stem reserve mobilization. The development of heat‐tolerant wheat genotypes through screening, selection and breeding using genetic engineering, exogenous application of osmoprotectants and agronomic approaches is a high priority. This review discusses the impact of heat stress on flower development and fertilization, grain development and reproductive failure in wheat and outlines strategies (i.e. breeding and selection, genetic engineering, molecular breeding and management) to improve heat tolerance in wheat.

Soil heterogeneity and earthworms independently promote growth of two bamboo species

Soils are commonly spatially heterogeneous and earthworms are widely distributed in terrestrial ecosystems. While both soil heterogeneity and earthworms can influence the performance of plants, whether they can interact to affect the growth of bamboo species has not been examined. In a greenhouse experiment, we planted two dwarf bamboo species, Sasa argenteosriata and Sasaella glabra, separately in a heterogeneous soil consisting of two different types of soil patches and in a homogeneous soil in which the two types of soil patches were evenly mixed. These soils were added with or without earthworms. Both S. argenteosriata and S. glabra grew more in the heterogeneous soil than in the homogeneous soil and in the soil with earthworms than in the soil without earthworms. Soil heterogeneity and earthworms did not interact to influence the performance of either bamboo species. Independent of the presence of earthworms, both bamboo species grew equally well in the two types of soil patches within the heterogeneous soil, indicating that the foraging behavior of bamboos is weak; this is likely because resource translocation between interconnected ramets located in different soil patches homogenized plant responses to different resource levels. These results indicate that a heterogeneous supply of nutrients may aid in the growth of bamboo species, and these actions should be integrated into the sustainable management of bamboo forests.

Capturing and Selecting Senescence Variation in Wheat.

Senescence is a highly quantitative trait, but in wheat the genetics underpinning senescence regulation remain relatively unknown. To select senescence variation and ultimately identify novel genetic regulators, accurate characterization of senescence phenotypes is essential. When investigating senescence, phenotyping efforts often focus on, or are limited to, the visual assessment of flag leaves. However, senescence is a whole-plant process, involving remobilization and translocation of resources into the developing grain. Furthermore, the temporal progression of senescence poses challenges regarding trait quantification and description, whereupon the different models and approaches applied result in varying definitions of apparently similar metrics. To gain a holistic understanding of senescence, we phenotyped flag leaf and peduncle senescence progression, alongside grain maturation. Reviewing the literature, we identified techniques commonly applied in quantification of senescence variation and developed simple methods to calculate descriptive and discriminatory metrics. To capture senescence dynamism, we developed the idea of calculating thermal time to different flag leaf senescence scores, for which between-year Spearman’s rank correlations of r ≥ 0.59, P < 4.7 × 10–5 (TT70), identify as an accurate phenotyping method. Following our experience of senescence trait genetic mapping, we recognized the need for singular metrics capable of discriminating senescence variation, identifying thermal time to flag leaf senescence score of 70 (TT70) and mean peduncle senescence (MeanPed) scores as most informative. Moreover, grain maturity assessments confirmed a previous association between our staygreen traits and grain fill extension, illustrating trait functionality. Here we review different senescence phenotyping approaches and share our experiences of phenotyping two independent recombinant inbred line (RIL) populations segregating for staygreen traits. Together, we direct readers toward senescence phenotyping methods we found most effective, encouraging their use when investigating and discriminating senescence variation of differing genetic bases, and aid trait selection and weighting in breeding and research programs alike.

Physiological Integration Increases Sexual Reproductive Performance of the Rhizomatous Grass Hierochloe glabra.

Clonal plants usually reproduce asexually through vegetative propagation and sexually by producing seeds. Physiological integration, the translocation of essential resources between ramets, usually improves vegetative reproduction. However, how physiological integration affects sexual reproduction has been less studied in clonal grasses. Here, we chose Hierochloe glabra, a major early spring forage of the eastern Eurasian steppe, and conducted a series of field experiments, including sampling reproductive ramets connected by tillering nodes to different numbers of vegetative ramets and 15N leaf labeling of ramet pairs at the seed-filling stage. In the natural populations of H. glabra, vegetative ramets were taller, had more and larger leaves, and greater biomass than reproductive ramets. Except for reproductive ramet biomass, sexual reproductive characteristics significantly increased with an increase in the number and biomass of vegetative ramets connected to tillering nodes. 15N labeling showed that vegetative ramets supplied nutrients to reproductive ramets through tillering nodes. Overall, our results indicate that significant differences in morphological characteristics and biomass allocation underlie resources translocation from vegetative ramets towards reproductive ramets. Physiological integration between different functional ramets can increase sexual reproductive performance, which will be beneficial to population persistence in H. glabra.

Clonal integration driven by source-sink relationships is constrained by rhizome branching architecture in a running bamboo species (Phyllostachys glauca): A 15N assessment in the field

Source-sink relationships and branching architecture are two determinants of clonal integration, but their joint effects on resource translocation are still unclear. Our aim was to elucidate the pattern and mechanism of resource translocation controlled by source-sink relationships and branching architecture. We conducted a 15N-tracing experiment in six plots of a running bamboo, Phyllostachys glauca, in the field. The immature ramets and mature ramets were defined as strong sinks and weak sinks according to their sink strength, and the territories of integrated ramets were classified into zero-barrier zones and barrier zones considering rhizome branching architecture. The translocation of 15N for all ramets showed a logarithmic pattern over time with a peak around the fifth week after labelling. Spatially, 15N was exported first to ramets in zero-barrier zones within three days and then to ramets in barrier zones within three weeks. Ramets in zero-barrier zones had a significantly higher translocation intensity (1653.2‰), speed (1.95 m/day) and amount (39.9 mg kg−1), and a shorter translocation time (three days) than ramets in barrier zones (61.3‰, 0.86 m/day, 2.3 mg kg−1 and 1.4 weeks, respectively). In zero-barrier zones, translocation intensity and amount in immature ramets were 6.7 and 3.4 times greater than those in mature ramets, respectively. In barrier zones, translocation traits (intensity, speed, time, amount) of immature ramets and mature ramets were similar. In addition, distance did not affect nitrogen translocation pattern or the effects of rhizome branching architecture and source-sink relationships on nitrogen translocation. The nitrogen translocation was mainly confined in zero-barrier zones by rhizome branching architecture, where source-sink relationships worked. In the clonal integration of P. glauca, source-sink relationships are the driving forces, while rhizome branching architecture acts as a flow restrictor. The results provide implications for spreading control and fertilizer applications on running bamboos.

Clonal integration enhances performance of an invasive grass

While many clonal plants are highly successful invaders, the contribution of clonal integration (i.e. the translocation of resources among ramets) to invasion is often unknown. We used model simulations to ask if clonal integration would facilitate photosynthate translocation, if the performance of daughter ramets might be enhanced by clonal integration, and if shaded ramets benefited relatively more from transferred photosynthate. Then, to test if photosynthate translocation augmented performance of emerging daughter ramets for a globally invasive grass (Imperata cylindrica), we combined a 13CO2 pulse‐chase experiment with a greenhouse experiment manipulating light levels and rhizome attachment. We found that acropetal photosynthate transfer occurred between all sampled parent–daughter ramet pairs and that this resource sharing led to higher biomass and tiller production when rhizomes between parent and daughter ramets were intact. We also found that the benefits of integration to recipient clones outweighed the costs to donors, since there was no reduction in parent plant performance due to sharing. Additionally, our data analyses show that photosynthate transfer was likely of greater benefit in overcoming growth constraints in shade than in full sun (posterior probability ~96.5%), a result that is further supported by our numerical simulations from a basic growth model. Thus, resource sharing among clonal plants may be a critical but underappreciated trait of invasive species. More generally, photosynthate transfer is a probable mechanism that explains why clonal integration can be particularly beneficial in heterogeneous resource environments.

Photoacclimation and Photoprotection of Juvenile Sporophytes of Macrocystis pyrifera (Laminariales, Phaeophyceae) Under High-light Conditions During Short-term Shallow-water Cultivation1.

This study was designed to understand better if and how juvenile sporophytes of Macrocystis pyrifera can photoacclimate to high-light conditions when transplanted from 10 to 3 meters over 7d. Acclimation of adult sporophytes to light regimes in the bathymetric gradient has been extensively documented. It primarily depends on photoacclimation and translocation of resources among blades. Among other physiological differences, juvenile sporophytes of M. pyrifera lack the structural complexity shown by adults. As such, juveniles may primarily depend on their photoacclimation capacities to maintain productivity and even avoid mortality under changing light regimes. However, little is known about how these mechanisms operate in young individuals. The capacity of sporophytes to photoacclimate was assessed by examining changes in their photosynthetic performance, pigment content, and bio-optical properties of the blade. Sporophytes nutritional status and oxidative damage were also determined. Results showed that juvenile sporophytes transplanted to shallow water were able to regulate light harvesting by reducing pigment concentration, and thus, absorptance and photosynthetic efficiency. Also, shallow-water sporophytes notably enhanced the dissipation of light energy as heat (NPQ) as a photoprotective mechanism. Generally, these adjustments allowed sporophytes to manage the absorption and utilization of light energy, hence reducing the potential for photo-oxidative damage. Furthermore, no substantial changes were found in the internal reserves (i.e., soluble carbohydrates and nitrogen) of these sporophytes. To our knowledge, these results are the first to provide robust evidence of photoprotective and photoacclimation strategies in juveniles of M. pyrifera, allowing them to restrict or avoid photodamage during shallow-water cultivation.

Variations in nutrient uptake, yield and nut quality of different pistachio cultivars grafted on Pistacia khinjuk rootstock

Nutrient accumulation in plant leaves provides empirical information about the uptake, translocation and utilization of available resources, which is ultimately reflected in yield. Several studies have reported that rootstock significantly affect nutrient uptake and yield in pistachio; however, little is known about the differences among cultivars of different origin grafted on the same rootstock. This study was conducted to assess the differences in nutrient uptake, yield and nut quality of different pistachio cultivars grafted on Pistacia khinjuk rootstock in Sanliurfa province, Turkey. An orchard with 14 different cultivars grafted on same rootstock was established in 1994 with 7 m × 5 m spacing. Leaf samples were collected at the beginning of fruit maturation and analyzed for N, P, K, Ca, Mg, Fe, Zn, Mn, and Cu contents. Yield and nut quality were evaluated at maturity. Significant differences were observed among cultivars for nutrient uptake, yield and nut quality. The highest N, P and K were accumulated by ‘Haciserifi’ cultivar, whereas the highest uptake of Ca, Mg and Cu was noted for ‘Mumtaz’ cultivar. Similarly, ‘Vahidi’ cultivar accumulated the highest amounts of Fe and Zn, whereas the highest accumulation of Mn was recorded for ‘Sel-15′ cultivar. The highest 100-fruit weight and yield were recorded for ‘Mumtaz’ cultivar. Similarly, the highest percentage of split nuts was recorded for ‘Sel-2′, ‘Sel-5′ and ‘Siirt’ cultivars, whereas the highest kernel ratio was noted for ‘Ohadi’ cultivar. Principal component analysis divided the cultivars in 3 groups. The cultivars in the first group had similar Cu, Mg, Ca, K accumulation, 100-fruit weight and yield, while the second group cultivars had similar accumulation of N, P, Zn and Fe. The third group had the cultivars with heterogenous accumulation of plant nutrients. It is concluded that nutrient accumulation, yield and quality of pistachio is not only influenced by rootstock; rather, grafted cultivars also significantly differ for nutrient uptake. Therefore, both rootstock and cultivars should be considered while establishing pistachio orchards for efficient utilization of available resources and better economic returns.

Nutrient addition does not increase the benefits of clonal integration in an invasive plant spreading from open patches into plant communities.

One benefit of clonal integration is that resource translocation between connected ramets enhances the growth of the ramets grown under stressful conditions, but whether such resource translocation reduces the performance of the ramets grown under favourable conditions has not produced consistent results. In this study, we tested the hypothesis that resource translocation to recipient ramets may reduce the performance of donor ramets when resources are limiting but not when resources are abundant. We grew Mikania micrantha stolon fragments (each consisting of two ramets, either connected or not connected) under spatially heterogeneous competition conditions such that the developmentally younger, distal ramets were grown in competition with a plant community and the developmentally older, proximal ramets were grown without competition. For half of the stolon fragments, slow-release fertiliser pellets were applied to both the distal and proximal ramets. Under both the low and increased soil nutrient conditions, the biomass, leaf number and stolon length of the distal ramets were higher, and those of the proximal ramets were lower when the stolon internode was intact than when it was severed. For the whole clone, the biomass, leaf number and stolon length did not differ between the two connection treatments. Connection did not change the biomass of the plant communities competing with distal ramets of M.micrantha. Although clonal integration may promote the invasion of M.micrantha into plant communities, resource translocation to recipient ramets of M.micrantha will induce a cost to the donor ramets, even when resources are relatively abundant.

Separating effects of clonal integration on plant growth during submergence and de-submergence

Responses to both submergence and de-submergence are important for evaluating flood tolerance of plants. Clonal integration (resource translocation between connected ramets within clones) has been shown to increase flood tolerance of amphibious clonal plants. However, no study has truly separated the effects of clonal integration during de-submergence from those during submergence. We grew 40 clonal fragments of the amphibious plant species Alternanthera philoxeroides, each consisting of two ramet systems, under half-submerged conditions (one ramet system submerged and the other un-submerged) for 30 d and then de-submerged for 20 d. To evaluate the effects of clonal integration during submergence, stolon connection between the two ramet systems was either severed or not on day 1, and 10 replicates of the fragments of each treatment were harvested on day 30. To evaluate the effects of clonal integration after de-submergence, the remaining 20 clonal fragments with connected stolons during submergence were de-submerged; half of them were subjected to stolon severing on day 31 and the remaining 10 fragments were not. All the 20 fragments for de-submergence were harvested on day 50. After 30 d of submergence, stolon connection between the submerged and the un-submerged ramets significantly increased growth, biomass allocation to roots and photosynthetic capacities of the submerged ramets, and also increased growth and photosynthetic capacities of the un-submerged ramets. Consequently, clonal integration significantly increased growth of the apical ramets, the basal ramets and the whole fragments. However, after 20 d of de-submergence, stolon connection did not significantly affect growth or photosynthetic capacities of either de-submerged or un-submerged ramets. The results suggest that clonal integration plays different roles during submergence and de-submergence. It increases performance of submerged ramets during submergence by translocation of photosynthates from un-submerged ramets, but plays little roles during de-submergence.

Implications of physiological integration of stolon interconnected plants for salinity management in soilless strawberry production

Abstract Salinity can be a greater problem in shallow soilless media than in field soils because of the small root zone volume that commonly occurs in such systems. Clonal integration (the capability of reciprocal resource translocation among interconnected plantlets through their shared stolon) can alleviate salinity injury in strawberry (Fragaria x ananassa ‘Albion’). Here we report the effect of clonal integration on leaf area, shoot and root dry biomass, net CO2 assimilation rate (AN), stomatal conductance (gs), intercellular CO2 (ci), transpiration (E), and instantaneous water use efficiency (WUE). Interconnected mother-daughter pairs of strawberry plants were grown in stirred solution culture under greenhouse conditions. Combinations with independent salinity levels on the mother and daughter side were imposed in a 4 × 3 complete randomized factorial design. Salinity levels of 1, 3, 6 and 9 dS m−1 were established by adding calcium chloride (CaCl2) and sodium chloride (NaCl) as needed to a 1 dS/m nutrient solution. Interconnected daughter plants grew in 0.2 CaSO4, or the 1 dS m−1 nutrient solution, or the same solution supplied to the mother plant. Values of all measured attributes decreased with salinity, with the exception of Ci, which increased at the highest salinity combination of mother and daughter plants. In contrasting salinity conditions, clonal integration ameliorated salt stress in mother plants through water transfer from daughter to mother plants. Interclonal resource translocation was mainly driven by the contrast in stress intensity between mother and daughter plants.

The direction of carbon and nitrogen fluxes between ramets in Agrostis stolonifera changes during ontogeny under simulated competition for light.

Resource sharing is universal among connected ramets of clonal plants and is driven both by the developmental status of the ramets and the resource gradients. Above-ground competition forms spatial light gradients, but the role of resource sharing in such competition is unclear. We examined translocation of resources between mother and daughter ramets of Agrostis stolonifera under light heterogeneity throughout ramet ontogeny. We labelled ramets with 13C and 15N to estimate the bidirectional translocation of resources at three developmental stages of the daughters. In addition, we compared the final biomass of integrated and severed ramets in order to estimate the effect of integration on growth. Young developing daughters were supported by carbon, whereas nitrogen was only translocated towards daughters at the beginning of rooting, regardless of the light conditions. Shading of mothers was a major determinant of resource translocation between developed ramets, with carbon being preferentially moved to daughters from shaded mothers while nitrogen translocation was limited from daughters to shaded mothers. Surprisingly, the absolute amounts of translocated resources did not decline during development. Growth of daughters was enhanced by integration regardless of the shading. Overall, A. stolonifera maximizes the resource translocation pattern in order to enable it to spread from unfavourable habitats, rather than compensating for light heterogeneity among ramets.

Clonal integration is beneficial for resource sharing in a creeping amphibian herb (Alteranthera philoxeroides)

Clonal integration facilitates the growth and reproduction of clonal plants by providing the ability to share resources among ramets in heterogeneous environments. The benefits of clonal integration for plant growth may depend on a contrast in resource availability and may encounter costs, especially when a young part of the clone is growing across a border between richer and poorer conditions than the old part. We studied a clonal amphibian plant growing across a border between an aquatic and a terrestrial ecosystem, which typically differ in the availability of resources. We asked whether the young part of the clone is supporting the old part with phosphorus and whether this support has costs. We performed an experiment with Alternanthera philoxeroides where plants grow from water to a terrestrial habitat. The terrestrial habitat had either a low or high phosphorus supply, and the connection between the old and young parts of the clone was either left intact or split. We determined that the young part of the clone growing in a terrestrial habitat supported the old part with phosphorus when growing on a substrate rich in phosphorus. We have found no cost of this resource translocation; on the contrary, whole clones increased not only their accumulation of phosphorus, but also of nitrogen. Our study shows how an amphibian plant may profit from heterogeneous habitats by resource sharing in a clonal network.

Clonal integration facilitates spread of Paspalum paspaloides from terrestrial to cadmium-contaminated aquatic habitats.

Cadmium (Cd) is a hazardous environmental pollutant with high toxicity to plants, which has been detected in many wetlands. Clonal integration (resource translocation) between connected ramets of clonal plants can increase their tolerance to stress. We hypothesised that clonal integration facilitates spread of amphibious clonal plants from terrestrial to Cd-contaminated aquatic habitats. The spread of an amphibious grass Paspalum paspaloides was simulated by growing basal older ramets in uncontaminated soil connected (allowing integration) or not connected (preventing integration) to apical younger ramets of the same fragments in Cd-contaminated water. Cd contamination of apical ramets of P.paspaloides markedly decreased growth and photosynthetic capacity of the apical ramets without connection to the basal ramets, but did not decrease these properties with connection. Cd contamination did not affect growth of the basal ramets without connection to the apical ramets, but Cd contamination of 4 and 12mg·l-1 significantly increased growth with connection. Consequently, clonal integration increased growth of the apical ramets, basal ramets and whole clones when the apical ramets were grown in Cd-contaminated water of 4 and 12mg·l-1 . Cd was detected in the basal ramets with connection to the apical ramets, suggesting Cd could be translocated due to clonal integration. Clonal integration, most likely through translocation of photosynthates, can support P.paspaloides to spread from terrestrial to Cd-contaminated aquatic habitats. Amphibious clonal plants with a high ability for clonal integration are particularly useful for re-vegetation of degraded aquatic habitats caused by Cd contamination.

Initial evidence for simultaneous, bi-directional sap flow in roots of interconnected aspen ramets (Populus tremuloides)

Approximately 40% of the world’s currently known plant species exhibit some form of clonality. Yet, little is known about the extent of clonal integration (e.g. the sharing and translocation of resources among ramets), especially in woody species. Aspen (Populus tremuloides Michx.), a widespread clonal tree species of high ecological value and conservation concern, is an excellent model species to study clonal integration. We used sap flow sensors on the root system of aspen located in the Fraser Experimental Forest (Colorado) to quantify water fluxes, assess directionality of flow and assess responses to a root severing experiment. Our results indicate simultaneous, bi-directional flow in roots with 3–4 times more flow in one direction. Flow towards ramets that were subjected to severing of roots (except the measured root) decreased considerably, and an increase in root flow ‘down the line’ towards connected, untreated ramets suggests complex interactions within the root system. Our results are intriguing and provide a first account of directionality of flow and distribution of water in an interconnected root system of a clonal tree species. Based on these findings, we formulate a set of further research questions and discuss methodology and experiments to test them.

Evidence for unexpected higher benefits of clonal integration in nutrient-rich conditions

Physiologically integrated clonal plants cope better with spatial heterogeneity due to their ability to share resources among ramets. According to theoretical predictions and experimental evidence, such benefits of resource sharing should increase with higher patch quality of an exporting ramet and lower patch quality of an importing ramet. This study investigated the effect of spatial heterogeneity in nutrient availability on benefits of clonal integration under plausible scenarios of clonal spread, in which more developed ramets give rise to new ones. Pairs of mother and daughter ramets of a stoloniferous grass, Agrostis stolonifera, were grown in various nutrient conditions. Disconnected pairs of ramets were used as controls. Results showed considerable benefits of integration for developmentally younger daughters and no costs for older mothers in all treatments. Surprisingly, benefits of integration were more pronounced in nutrient-rich daughters, and allocation to integrated daughters decreased with increasing nutrient level of mothers. In addition, integration in general increased root-to-shoot ratio of daughters. One possible explanation of the observed patterns may be prevailing translocation of photosynthates rather than nutrients. Daughters also responded to nutrients by changes in clonal architecture. Number of stolons increased, and maximum stolon length decreased in high nutrient levels. Integration increased maximum stolon length in small daughters. The architectural responses are generally in accord with the foraging behaviour concept. Overall, our results suggest that resource translocation within a clonal fragment need not be easily predictable from a gradient of resource availability.

Biomass loss reduces growth and resource translocation in giant kelp Macrocystis pyrifera

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 562:65-77 (2016) - DOI: https://doi.org/10.3354/meps11949 Biomass loss reduces growth and resource translocation in giant kelp Macrocystis pyrifera Michael D. Fox1,2,* 1Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA 2Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA *Corresponding author: fox@ucsd.edu ABSTRACT: The biomass dynamics of primary producers have important implications for the structure and function of ecosystems. Along the wave-swept coastline of central California, USA, biomass removal by wave action is a key driver in the primary productivity of giant kelp forests, yet the mechanisms of regrowth within giant kelp Macrocystis pyrifera are not well understood. To examine the physiological consequences of biomass loss on Macrocystis, a manipulative experiment was used to simulate biomass removal by wave action. Growth rates were measured as the number of new fronds produced through time, and the δ13C and δ15N values of juvenile fronds were used as a proxy for carbon and nitrogen translocation in support of growth. The experimental removal of biomass significantly constrained the growth of new fronds and, under extreme levels, led to mortality. The growth rate and isotopic composition of juvenile fronds on sporophytes with a portion of canopy biomass intact recovered to pre-disturbance values within 4 mo. In contrast, a reduction in growth rates as well as a permanent depletion in δ13C and δ15N values was observed when the canopy was completely removed and the magnitude scaled with biomass loss. These results suggest that the translocation of carbon and nitrogen to juvenile fronds from near-surface biomass is a critical process affecting growth in giant kelp. The spatial variability and physiological consequences of biomass loss among individuals may therefore play an important role in the biomass dynamics of giant kelp forests across multiple temporal and spatial scales. KEY WORDS: Stable isotopes · Carbon · Nitrogen · Resource allocation · Disturbance · Recovery Full text in pdf format Supplementary material PreviousNextCite this article as: Fox MD (2016) Biomass loss reduces growth and resource translocation in giant kelp Macrocystis pyrifera. Mar Ecol Prog Ser 562:65-77. https://doi.org/10.3354/meps11949 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 562. Online publication date: December 29, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.