title: Drought-induced shoot dieback starts with massive root xylem embolism and variable depletion of nonstructural carbohydrates in seedlings of two tree species.
abstract: Combining hydraulic- and carbon-related measurements helps to understand drought-induced plant mortality. Here, we investigated the role that plant respiration (R) plays in determining carbon budgets under drought. We measured the hydraulic conductivity of stems and roots, and gas exchange and nonstructural carbohydrate (NSC) concentrations of leaves, stems and roots of seedlings of two resprouting species exposed to drought or well-watered conditions: Ulmus minor (riparian tree) and Quercus ilex (dryland tree). With increasing water stress (occurring more rapidly in larger U. minor), declines in leaf, stem and root R were less pronounced than that in leaf net photosynthetic CO2uptake (Pn). Daytime whole-plant carbon gain was negative below -4 and -6 MPa midday xylem water potential in U. minor and Q. ilex, respectively. Relative to controls, seedlings exhibiting shoot dieback suffered c. 80% loss of hydraulic conductivity in both species, and reductions in NSC concentrations in U. minor. Higher drought-induced depletion of NSC reserves in U. minor was related to higher plant R, faster stomatal closure, and premature leaf-shedding. Differences in drought resistance relied on the ability to maintain hydraulic conductivity during drought, rather than tolerating conductivity loss. Root hydraulic failure elicited shoot dieback and precluded resprouting without root NSC reserves being apparently limiting for R.
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.
authors: Jesús
authors: J
authors: Rodríguez-Calcerrada
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.
authors: Meng
authors: M
authors: Li
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.|Hawkesbury Institute for the Environment, UWS, Science Road, Richmond, 2753, NSW, Australia.
authors: Rosana
authors: R
authors: López
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.|Hawkesbury Institute for the Environment, UWS, Science Road, Richmond, 2753, NSW, Australia.
authors: Francisco Javier
authors: FJ
authors: Cano
authors: Institute of Dendrology, Polish Academy of Sciences, Kórnik, 62-035, Poland.
authors: Jacek
authors: J
authors: Oleksyn
authors: ARC Centre of Excellence in Plant Energy Biology, Division of Plant Sciences, Research School of Biology, The Australian National University, Building 134, Canberra, ACT, 2601, Australia.
authors: Owen K
authors: OK
authors: Atkin
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.
authors: Pilar
authors: P
authors: Pita
authors: Department of Forest Ecology and Genetics, Forest Research Centre, INIA, Avda. A Coruña km 7.5, 28040, Madrid, Spain.
authors: Ismael
authors: I
authors: Aranda
authors: Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain.
authors: Luis
authors: L
authors: Gil
mesh_terms: D002241:Carbohydrates / Q000737:chemistry*; D002244:Carbon / Q000378:metabolism; D019069:Cell Respiration; D055864:Droughts; D005740:Gases / Q000378:metabolism; D018517:Plant Roots / Q000502:physiology*; D018520:Plant Shoots / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D029963:Quercus / Q000502:physiology; D036226:Seedlings / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D013045:Species Specificity; D013227:Steam; D014197:Trees / Q000502:physiology*; D034403:Ulmus / Q000502:physiology; D014867:Water; D052584:Xylem / Q000502:physiology*
chemical_list: D002241:Carbohydrates; D005740:Gases; D013227:Steam; D014867:Water; D002244:Carbon
keywords: carbon starvation; cavitation; die-off; forest decline; phloem failure; plant mortality; stem growth