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Shade‐induced reduction of stem nonstructural carbohydrates increases xylem vulnerability to embolism and impedes hydraulic recovery in Populus nigra
Author(s) -
Tomasella Martina,
Casolo Valentino,
Natale Sara,
Petruzzellis Francesco,
Kofler Werner,
Beikircher Barbara,
Mayr Stefan,
Nardini Andrea
Publication year - 2021
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.17384
Subject(s) - xylem , hydraulic conductivity , shading , biology , botany , bark (sound) , water transport , sugar , horticulture , environmental science , ecology , soil water , soil science , water flow , biochemistry , art , visual arts
Summary Nonstructural carbohydrates (NSCs) have been suggested to affect xylem transport under fluctuating water availability, but conclusive evidence is still lacking. We tested the effect of shade‐induced NSC depletion on xylem vulnerability to embolism and hydraulic recovery on Populus nigra saplings. Vulnerability was assessed in light‐exposed (L) and shaded (S) plants with the hydraulic method, and in vivo with the optical method and X‐ray micro‐computed tomography. Plants were stressed to 80% loss of hydraulic conductance (PLC) and re‐irrigated to check for possible recovery. We measured PLC, bark and wood NSC content, as well as xylem sap pH, surface tension ( γ sap ) and sugar concentration, before, during and after drought. Shading induced depletion of stem NSC (mainly starch) reserves. All methods converged in indicating higher xylem vulnerability in S than in L plants. This difference was not explained by xylem vessel and pit anatomy or by γ sap . Shading impeded sap acidification and sugar accumulation during drought in S plants and prevented hydraulic recovery, which was observed in L plants. Our results highlight the importance of stem NSCs to sustain xylem hydraulic functioning during drought and suggest that light and/or adequate stem NSC thresholds are required to trigger xylem sap chemical changes involved in embolism recovery.