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PremiseThe young seedling life stage is critical for reforestation after disturbance and for species migration under climate change, yet little is known regarding their basic hydraulic function or vulnerability to drought. Here, we sought to characterize responses to desiccation including hydraulic vulnerability, xylem anatomical traits, and impacts on other stem tissues that contribute to hydraulic functioning. MethodsLarix occidentalis,Pseudotsuga menziesii, andPinus ponderosa(all ≤6 weeks old) were imaged using x‐ray computed microtomography during desiccation to assess seedling biomechanical responses with concurrently measured hydraulic conductivity (ks) and water potential (Ψ) to assess vulnerability to xylem embolism formation and other tissue damage. ResultsIn non‐stressed samples for all species, pith and cortical cells appeared circular and well hydrated, but they started to empty and deform with decreasingΨwhich resulted in cell tearing and eventual collapse. Despite the severity of this structural damage, the vascular cambium remained well hydrated even under the most severe drought. There were significant differences among species in vulnerability to xylem embolism formation, with 78% xylem embolism inL. occidentalisbyΨof −2.1 MPa, but only 47.7% and 62.1% inP. ponderosaandP. menziesiiat −4.27 and −6.73 MPa, respectively. ConclusionsLarix occidentalisseedlings appeared to be more susceptible to secondary xylem embolism compared to the other two species, but all three maintained hydration of the vascular cambium under severe stress, which could facilitate hydraulic recovery by regrowth of xylem when stress is relieved.
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The xylem of anisohydric Quercus alba L. is more vulnerable to embolism than isohydric codominants
Abstract The coordination of plant leaf water potential (ΨL) regulation and xylem vulnerability to embolism is fundamental for understanding the tradeoffs between carbon uptake and risk of hydraulic damage. There is a general consensus that trees with vulnerable xylem more conservatively regulate ΨLthan plants with resistant xylem. We evaluated if this paradigm applied to three important eastern US temperate tree species,Quercus albaL.,Acer saccharumMarsh. andLiriodendron tulipiferaL., by synthesizing 1600 ΨLobservations, 122 xylem embolism curves and xylem anatomical measurements across 10 forests spanning pronounced hydroclimatological gradients and ages. We found that, unexpectedly, the species with the most vulnerable xylem (Q. alba) regulated ΨLless strictly than the other species. This relationship was found across all sites, such that coordination among traits was largely unaffected by climate and stand age.Quercusspecies are perceived to be among the most drought tolerant temperate US forest species; however, our results suggest their relatively loose ΨLregulation in response to hydrologic stress occurs with a substantial hydraulic cost that may expose them to novel risks in a more drought‐prone future.
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- PAR ID:
- 10361760
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Plant, Cell & Environment
- Volume:
- 45
- Issue:
- 2
- ISSN:
- 0140-7791
- Page Range / eLocation ID:
- p. 329-346
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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