High‐resolution computed tomography reveals dynamics of desiccation and rehydration in fern petioles of a desiccation‐tolerant fern

Abstract

Summary Desiccation‐tolerant (DT) plants can dry past −100 MPa and subsequently recover function upon rehydration. Vascular DT plants face the unique challenges of desiccating and rehydrating complex tissues without causing structural damage. However, these dynamics have not been studied in intact DT plants. We used high resolution micro‐computed tomography (microCT), light microscopy, and fluorescence microscopy to characterize the dynamics of tissue desiccation and rehydration in petioles (stipes) of intact DT ferns. During desiccation, xylem conduits in stipes embolized before cellular dehydration of living tissues within the vascular cylinder. During resurrection, the chlorenchyma and phloem within the stipe vascular cylinder rehydrated before xylem refilling. We identified unique stipe traits that may facilitate desiccation and resurrection of the vascular system, including xylem conduits containing pectin (which may confer flexibility and wettability); chloroplasts within the vascular cylinder; and an endodermal layer impregnated with hydrophobic substances that impede apoplastic leakage while facilitating the upward flow of water within the vascular cylinder. Resurrection ferns are a novel system for studying extreme dehydration recovery and embolism repair in the petioles of intact plants. The unique anatomical traits identified here may contribute to the spatial and temporal dynamics of water movement observed during desiccation and resurrection.

Drought‐induced lacuna formation in the stem causes hydraulic conductance to decline before xylem embolism in Selaginella

“…Here we demonstrate that considerable (up to 80%) reductions in K shoot in two Selaginella species precede embolism formation. Visualization of the internal anatomy of the stem by micro-CT revealed that, similar to desiccation-tolerant ferns (Holmlund et al, 2019), a physical separation between the cortex and the vascular cylinder occurred when Ψ declines in Selaginella. Unlike in desiccation-tolerant ferns, the large, air- filled lacuna in Selaginellaforms at high Ψ before embolism formation and is the result of water loss and cell collapse in the cortex, not from the vascular tissue collapsing within the vascular cylinder.…”

Primary tissues may affect estimates of cavitation resistance in ferns

“…Most ferns are not well adapted to water deficit, but studies have indicated that variation in species drought tolerance is consistent with habitat and species life history strategy (Watkins et al, 2010;Burns et al, 2016;Holmlund et al, 2016Holmlund et al, , 2019Holmlund et al, , 2020. Drought tolerance in plants is linked to cavitation resistance, that is the degree to which the xylem is susceptible to dysfunction by air entry.…”

Tracking the Biological Incorporation of Exogenous Molecules into Cellulose Fibers with Non‐Radioactive Iodinated Glucose

“…[19] Also, these compounds have been utilized for the spatial, in-vivo, dynamic visualization of water movement in roots [20] or conductive conduits (xylem) during tissue desiccation/rehydration, embolism resistance [21] and repair. [22] Interestingly, the combination of CT and non-radioactive, metabolizing iodinated glucose 2-deoxy-2-iodo-D-glucose (DIG) for exploring sugar transport and accumulation in smaller plants still remains largely unexplored.…”