Tracheid buckling buys time, foliar water uptake pays it back: Coordination of leaf structure and function in tall redwood trees

Authors: CHIN, ALANA - University Of California, Davis; GUZMAN-DELGADO, PAULA - University Of California, Davis; SILLETT, STEPHEN - Humboldt State University; KERHOULAS, LUCY - Humboldt State University; AMBROSE, ANTHONY - University Of California; McElrone, Andrew; ZWIENIECKI, MACIEJ - University Of California, Davis

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2022
Publication Date: 6/23/2022
Citation: Chin, A., Guzman-Delgado, P., Sillett, S.C., Kerhoulas, L., Ambrose, A., McElrone, A.J., Zwieniecki, M. 2022. Tracheid buckling buys time, foliar water uptake pays it back: Coordination of leaf structure and function in tall redwood trees. Plant Cell and Environment. 45(9):2607-2616. https://doi.org/10.1111/pce.14381.
DOI: https://doi.org/10.1111/pce.14381

Interpretive Summary:

Technical Abstract: The crowns of tall redwoods (Sequoia sempervirens (D.Don) Endl.) extend from full sun to deep shade (< 10 % light) as far as 88 m beneath the treetop, with highly plastic leaves capable of acclimating their structure and physiology to a wide spectrum of ecological conditions. While leaves in full sun develop in a constantly demanding environment, below the upper crown, leaves must tolerate variability caused by sunflecks, penetrating shafts of direct light capable of raising leaf temperatures by as much as 20°C in one minute. Such a temperature fluctuation can increase the vapor pressure deficit (VPD) by ~ 1-2 kPa, instantaneously increasing transpirational demand and hydraulic tension, if stomata fail to regulate water loss. Here we show that transfusion tracheids in redwood leaves reduce their volume due to buckling, suppling water to sustain rapid increases in evaporation, thus providing a time safety-margin sufficient for leaves to reduce stomatal conductance, and a ‘stop-point’ for the transmission of tension. The capacity of transfusion tracheids to release water appears to decrease with height, while peak variation in release capacity in the middle crown where microclimate is most variable. Absorption of water through leaf surfaces restores collapsed and air-filled transfusion tracheids, allowing for repetitive cycles of buckling to support leaf survival in the variable deep-crown environment.