Foliar water uptake enables embolism removal in excised twigs of Avicennia marina

Abstract

Embolism refilling is thought to require relaxation of xylem tension, and it is unclear whether and how tall trees or plants growing in arid or saline soils recover from embolism. We tested whether foliar water uptake could enable embolism refilling in dehydrated twigs of the grey mangrove (Avicennia marina).Four dehydrated twigs were imaged by laboratory-based micro-computed tomography before and after wetting leaves.Emboli were observed in dehydrated stems and leaves. Embolism decreased with increasing distance from the cut end of stems, suggesting that stem emboli were caused by cutting. A significant (P = 0.026) c. 80% reduction in the embolised area was observed in leaves between the start and the end of the experiment (29 AE 10 h after wetting). Embolus diameter was unaffected by wetting.Embolism refilling occurred slowly, in stems embolised by cutting and leaves embolised by cutting and/or dehydration. The lack of response of embolus diameter to wetting suggests that capillarity was not the main mechanism for refilling. Results show that excised twigs of A. marina are able to recover from embolism by absorption of atmospheric water and call for studies under natural conditions.

Ghosts of dry seasons past: Legacy of severe drought enhances mangrove salinity tolerance through coordinated cellular osmotic and elastic adjustments

“…Limitations of decreasing TSM and increasing WS deficits might be offset by foliar water uptake as suggested by Nguyen, Meir, Sack, et al (2017). Indeed, widespread capacity for foliar water uptake occurs in mangroves (Bryant, Fuenzalida, Zavafer, et al, 2021; Hayes et al, 2020) including A. corniculatum (Schaepdryver et al, 2022), enabling recovery of leaf hydraulic conductance (Fuenzalida et al, 2019), embolism repair (Fuenzalida et al, 2022), protection of stem hydraulic function (Coopman et al, 2021) and long‐term benefits to turgor‐dependent growth (Schreel et al, 2019; Steppe et al, 2018). However, greater reliance on atmospheric water may result in greater vulnerability to drought conditions that lead to increased estuarine salinity, while drier atmospheric conditions would also reduce the occurrence of foliar uptake of atmospheric water.…”

Bark water uptake through lenticels increases stem hydration and contributes to stem swelling

“…Therefore, BWU measured here would fill 31% of that hydration deficit. FWU in A. marina can increase ψ above those achievable through the roots (Coopman et al, 2021; Nguyen, Meir, Sack, et al, 2017), drive turgor‐driven growth spurts (Schreel et al, 2019; Steppe et al, 2018), repair embolism (Fuenzalida, Blacker, et al, 2022), and sustain high rates of leaf transpiration for more than 120 min in high salinity environments (Nguyen, Meir, Sack, et al, 2017). Therefore, BWU co‐occurring with FWU could immediately improve hydration where demand for water is greatest (Mason Earles et al, 2016).…”

“…Therefore, to achieve hydration greater than that of ψ salinity , FWU or BWU is required. Indeed, a diversity of pathways for FWU has been found in many species of mangrove (e.g., Bryant et al, 2021; Fuenzalida, Blacker, et al, 2022; Hayes et al, 2020; Schaepdryver et al, 2022) demonstrating widespread capacity for top‐down rehydration.…”

“…A. marina is the most widely distributed mangrove globally (Morrisey et al, 2010), capable of tolerating hypersaline conditions up to twice that of seawater (Reef et al, 2012). FWU in A. marina demonstrates capacity for top‐down rehydration (Coopman et al, 2021; Fuenzalida, Blacker, et al, 2022; Nguyen, Meir, Sack, et al, 2017; Schreel et al, 2019; Steppe et al, 2018); however, capacity for BWU remains untested. We tested the following hypotheses: …”

Leaf traits and fog harvest potential in xerophytic plants

“…New research questions arise from the data evaluated for leaf traits, such as whether water captured from fog can enter the leaf interior to be used in physiological processes, such as photosynthesis, or to maintain water relations and avoid/ recover cavitation (Guzmán-Delgado et al 2018, Coopman et al 2021, Fuenzalida et al 2023. Further research should explore even more detailed traits on the leaf surface, such as trichomes, cuticular waxes, and hydathodes, which could be responsible for processes such as water retention, hydrophobicity, and water resistance to flow.…”