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Physiology

Physiological integration of connected balsam poplar ramets

Profile image of Francine TremblayFrancine Tremblay

2016, Tree physiology

https://doi.org/10.1093/TREEPHYS/TPV142
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10 pages

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Abstract

Clonal integration between ramets can be an ecological advantage of clonal plant species in environments where resources are patchily distributed. We investigated physiological integration among Populus balsamifera L. ramets under drought stress in order to demonstrate water sharing between connected ramets. Pairs of connected ramets were grown in separate pots in the greenhouse where half of ramets had the parental root connection severed and half were left intact. Drought stress was applied to one ramet, and growth, specific leaf area (SLA), net photosynthesis, stomatal conductance, leaf water potential and carbon isotopic composition (δ(13)C) were measured after an 8-week growing period. Droughted ramets connected to watered ramets were able to maintain high gas exchange activity and water potential, similar to watered ramets. Leaf water potential and SLA results showed that the root connection was more beneficial for proximal compared with distal ramets. The parental root connec...

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  • Tree Physiology
  • Forestry Sciences
  • Plant Leaves
  • Stress Physiological

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

    Folia Geobotanica, 2017

    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, bidirectional 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.

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    Fructan dynamics in the underground organs of Chresta exsucca (Asteraceae), a dry season flowering species
    CINARA ABRAAO

    Acta Botanica Brasilica, 2017

    Climatic seasonality has an infl uence on the phenology of native Cerrado plants. Herbs and subshrubs tend to fl ower in the rainy season, although some species of these habits fl ower in the dry season. Reserve carbohydrates, stored in the underground organs, are used to support phases of high energy-demand, but also may protect plants from damage during periods of environmental limitation. In this study we evaluated variation in fructan levels in the underground organs of fi eld-grown plants of Chresta exsucca among diff erent phenological phases. Chresta exsucca fl owers in the dry season and possesses a diff use underground system, which stores inulin-type fructans. Resprouting was continual during the sampling period. Oligosaccharide content was always higher than polysaccharide content, except during senescence, the only phase with an oligosaccharide: polysaccharide ratio < 1. Fructan accumulation occurred during vegetative growth until fl owering. Fructan mobilization was prominent during resprouting until the beginning of vegetative growth. Fructans stored in the underground organs of C. exsucca serve to fulfi ll the energetic demands of development and maintenance of this complex structure. In this way, fructans are essential to the persistence of this species in the environment of the Cerrado by ensuring reproduction in harsh conditions, such as drought.

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    Cooperative root graft networks benefit mangrove trees under stress
    Jorge Lopez-Portillo

    Communications biology, 2021

    The occurrence of natural root grafts, the union of roots of the same or different trees, is common and shared across tree species. However, their significance for forest ecology remains little understood. While early research suggested negative effects of root grafting with the risk of pathogen transmission, recent evidence supports the hypothesis that it is an adaptive strategy that reduces stress by facilitating resource exchange. Here, by analysing mangrove root graft networks in a non-destructive way at stand level, we show further evidence of cooperation-associated benefits of root grafting. Grafted trees were found to dominate the upper canopy of the forest, and as the probability of grafting and the frequency of grafted groups increased with a higher environmental stress, the mean number of trees within grafted groups decreased. While trees do not actively 'choose' neighbours to graft to, our findings point to the existence of underlying mechanisms that regulate 'optimal group size' selection related to resource use within cooperating networks. This work calls for further studies to better understand tree interactions (i.e. network hydraulic redistribution) and their consequences for individual tree and forest stand resilience.

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