Losing half the conductive area hardly impacts the water status of mature trees

Dietrich, Lars; Hoch, Günter; Kahmen, Ansgar; Körner, Christian

doi:10.1038/s41598-018-33465-0

Cited by 49 publications

(39 citation statements)

References 40 publications

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“…The activation of more conduits under higher pressure gradients observed here substantiates the hypothesis that more conduits could be employed to overcome flow reductions due to damage, clogging and/or gel release. Results from staining experiments further corroborate the redundancy of the xylem conductive system for normal or low flows (Korner, 2019), as supported by a recent study showing that a tree stem may be cut in half with minimal effect on the canopy water relations (Dietrich, Hoch, Kahmen, & Körner, 2018).…”

Section: Resultssupporting

confidence: 72%

Persistent decay of fresh xylem hydraulic conductivity varies with pressure gradient and marks plant responses to injury

Bonetti

Breitenstein

Fatichi

et al. 2020

Plant Cell & Environment

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Defining plant hydraulic traits is central to the quantification of ecohydrological processes ranging from land‐atmosphere interactions, to tree mortality and water‐carbon budgets. A key plant trait is the xylem specific hydraulic conductivity (Kx), that describes the plant's vascular system capacity to transport water. While xylem's vessels and tracheids are dead upon maturity, the xylem is neither inert nor deadwood, various components of the sapwood and surrounding tissue remaining alive and functional. Moreover, the established definition of Kx assumes linear relations between water flux and pressure gradient by tacitly considering the xylem as a “passive conduit”. Here, we re‐examine this notion of an inert xylem by systematically characterizing xylem flow in several woody plants using Kx measurements under constant and cyclic pressure gradients. Results show a temporal and pressure gradient dependence of Kx. Additionally, microscopic features in “living branches” are irreversibly modified upon drying of the xylem, thus differentiating the macroscopic definition of Kx for living and dead xylem. The findings highlight the picture of the xylem as a complex and delicate conductive system whose hydraulic behaviour transcends a passive gradient‐based flow. The study sheds new light on xylem conceptualization, conductivity measurement protocols, in situ long‐distance water transport and ecosystem modelling.

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Section: Resultssupporting

confidence: 72%

Persistent decay of fresh xylem hydraulic conductivity varies with pressure gradient and marks plant responses to injury

Bonetti

Breitenstein

Fatichi

et al. 2020

Plant Cell & Environment

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show abstract

“…Plants may maintain transpiration and ‘safe’ water potentials even with only parts of their conductive area (Dietrich, Hoch, Kahmen, & Körner, ), and only a portion of their root system hydrated, potentially explaining why we did not find a difference in Ψ PD between the SRP and MP. Furthermore, redistributing water within their root system and releasing it into the soil can be beneficial to the plant (Prieto et al, ; Ryel et al, ).…”

Section: Discussionmentioning

confidence: 80%

Water potential gradient, root conduit size and root xylem hydraulic conductivity determine the extent of hydraulic redistribution in temperate trees

et al. 2020

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Hydraulic redistribution (HR) of soil water through plant roots is widely described; however its extent, especially in temperate trees, remains unclear. Here, we quantified HR of five temperate tree species. We hypothesized that both, HR within a plant and into the soil increase with higher water‐potential gradients, larger root conduit diameters and root‐xylem hydraulic conductivities as HR driving factors. Saplings of conifer (Picea abies, Pseudotsuga menziesii), diffuse‐porous (Acer pseudoplatanus) and ring‐porous species (Castanea sativa, Quercus robur) were planted in split‐root systems, where one plant had its roots split between two pots with different water‐potential gradients (0.23–4.20 MPa). We quantified HR via deuterium labelling. Species redistributed 0.39 ± 0.14 ml of water overnight (0.08 ± 0.01 ml/g root mass). Higher pre‐dawn water‐potential gradients, hydraulic conductivities and larger conduits significantly increased HR quantity. Hydraulic conductivity was the most important driving factor on HR amounts, within the plants (0.03 ± 0.01 ml/g) and into the soil (0.06 ± 0.01 ml/g). Additional factors as soil‐root contact should be considered, especially when calculating water transfer into the soil. Nevertheless, trees maintaining high‐xylem hydraulic conductivity showed higher HR amounts, potentially making them valuable ‘silvicultural tools’ to improve plant water status. A free Plain Language Summary can be found within the Supporting Information of this article.

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“…These thresholds are defined based upon observational (Adams et al ., 2017) and experimental studies showing drought‐induced mortality to be correlated with between 50% (Brodribb & Cochard, 2009) and 88% (Urli et al ., 2013) loss of water transport function due to cavitation. Although this mode of mortality is described as ‘hydraulic failure’, it is clear this range of stem xylem damage is insufficient to cause accelerated tissue dehydration leading to organ death (Dietrich et al ., 2018). Assuming that the causal connection found here in tomato leaves between leaf cavitation and tissue death provides a general explanation for drought damage caused by hydraulic failure, then xylem thresholds for leaf death would be expected to be much closer to 100% damage to the xylem supply network upstream of the mesophyll tissue.…”

Section: Discussionmentioning

confidence: 99%

Linking xylem network failure with leaf tissue death

et al. 2021

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Summary Global warming is expected to dramatically accelerate forest mortality as temperature and drought intensity increase. Predicting the magnitude of this impact urgently requires an understanding of the process connecting atmospheric drying to plant tissue damage. Recent episodes of forest mortality worldwide have been widely attributed to dry conditions causing acute damage to plant vascular systems. Under this scenario vascular embolisms produced by water stress are thought to cause plant death, yet this hypothetical trajectory has never been empirically demonstrated. Here we provide foundational evidence connecting failure in the vascular network of leaves with tissue damage caused during water stress. We observe a catastrophic sequence initiated by water column breakage under tension in leaf veins which severs local leaf tissue water supply, immediately causing acute cellular dehydration and irreversible damage. By highlighting the primacy of vascular network failure in the death of leaves exposed to drought or evaporative stress our results provide a strong mechanistic foundation upon which models of plant damage in response to dehydration can be confidently structured.

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Losing half the conductive area hardly impacts the water status of mature trees

Cited by 49 publications

References 40 publications

Persistent decay of fresh xylem hydraulic conductivity varies with pressure gradient and marks plant responses to injury

Persistent decay of fresh xylem hydraulic conductivity varies with pressure gradient and marks plant responses to injury

Water potential gradient, root conduit size and root xylem hydraulic conductivity determine the extent of hydraulic redistribution in temperate trees

Linking xylem network failure with leaf tissue death

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