The rates of starch depletion and hydraulic failure both play a role in drought-induced seedling mortality

• Published in: Annals of forest science. Vol. 81; no. 1; p. 27
• Main Authors: Trueba, Santiago, Muñoz, Noelia González, Burlett, Régis, Lamarque, Laurent J., Gibon, Yves, Gimeno, Teresa E., Kaisermann, Aurore, Benard, Camille, Lemaire, Cédric, Torres-Ruiz, Jose M., Wingate, Lisa, Delzon, Sylvain
• Format: Journal Article
• Language: English
• Published: London BioMed Central 02.08.2024; Springer Nature (since 2011)/EDP Science (until 2010); BMC
• Subjects: Biomedical and Life Sciences; drought; Ecology, environment; Embolism vulnerability; Environment; Forestry; Forestry Management; forests; Fructose; hydraulic conductivity; Hydraulic safety margin; Life Sciences; Light environment; mortality; Nonstructural carbohydrates; Research Paper; seedlings; species; starch; Sucrose; sugars; Tree Biology; tree mortality; tree physiology; trees; water stress; Wood Science & Technology; xylem; Hydraulic safety margin; Light environment; Embolism vulnerability; Sucrose; Nonstructural carbohydrates; Fructose; Ecophysiology
• ISSN: 1297-966X; 1286-4560; 1297-966X
• DOI: 10.1186/s13595-024-01246-7

Key message The elapsed times to deplete starch concentrations and to reach a null hydraulic safety margin were related to tree seedling mortality under experimental drought. Starch concentration showed an accelerated decline across all species during the early stages of dehydration, while the concentrations of soluble sugars and total nonstructural carbohydrates remained stable. Concomitant carbohydrate depletion and hydraulic failure drive seedling mortality under drought. Context Current upsurges of drought events are provoking impacts on tree physiology, resulting in forest mortality. Hydraulic dysfunction and nonstructural carbohydrate (NSC) depletion have been posited as the main mechanisms leading to plant mortality under drought. Aims This study explores the dynamics of the two mortality-inducing processes during drought stress using an experimental approach with 12 evergreen tree species. Methods Seedlings were subjected to drought until 100% mortality was observed. Midday (Ψ MD ) and predawn (Ψ PD ) water potentials, xylem pressure leading to a 50% loss of hydraulic conductivity (Ψ 50 ), along with NSC concentrations in different organs (leaves, stems, and roots) were measured regularly during drought. Results Total NSC concentrations and soluble sugar pools did not decline during drought. However, starch pools showed strong reductions early during drought stress as Ψ PD decreased, and the time leading to starch depletion emerged as a strong mortality predictor. Ψ 50 alone did not provide an accurate estimate of mortality, while the elapsed time to reach a null hydraulic safety margin (Ψ MD —Ψ 50  = 0) was related to seedling mortality. Conclusion Adopting a dynamic approach by estimating the times to consume both starch reserves and hydraulic safety margins is highly relevant to improve predictions of tree mortality under the current context of increasing global drought.