title: Recovery of Populus tremuloides seedlings following severe drought causing total leaf mortality and extreme stem embolism.
abstract: In contrast with other native Populus species in North America, Populus tremuloides (aspen) can successfully establish itself in drought-prone areas, yet no comprehensive analysis has been performed on the ability of seedlings to withstand and recover from a severe drought resulting in complete leaf mortality. Here, we subjected 4-month-old aspen seedlings grown in two contrasting soil media to a progressive drought until total leaf mortality, followed by a rewatering cycle. Stomatal conductance (g(s) ), photosynthesis and transpiration followed a sigmoid decline with declining fraction of extractable soil water values. Cessation of leaf expansion occurred close to the end of the linear-decrease phase, when g(s) was reduced by 95%. Leaf mortality started after g(s) reached the lowest values, which corresponded to a stem-xylem pressure potential (Ψ(xp)) of -2.0 MPa and a percent loss of stem hydraulic conductivity (PLC) of 50%. In plants with 50% leaf mortality, PLC values remained around 50%. Complete leaf mortality occurred at an average stem PLC of 90%, but all seedlings were able to resprout after 6-10 days of being rewatered. Plants decapitated at soil level before rewatering developed root suckers, while those left with a 4-cm stump or with their stems intact resprouted exclusively from axillary buds. Resprouting was accompanied by recovery of stem hydraulic conductivity, with PLC values around 30%. The percentage of resprouted buds was negatively correlated with the stem %PLC. Thus, the recovery of stem hydraulic conductivity appears as an important factor in the resprouting capacity of aspen seedlings following a severe drought.
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Xinong Road No. 26, Yangling, Shaanxi 712100, PR China.
authors.forename: Yanyuan
authors.initials: Y
authors.lastname: Lu
authors.forename: Maria Alejandra
authors.initials: MA
authors.lastname: Equiza
authors.forename: Xiping
authors.initials: X
authors.lastname: Deng
authors.forename: Melvin T
authors.initials: MT
authors.lastname: Tyree
mesh_terms: D055864:Droughts; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D032107:Populus / Q000502:physiology*; D013312:Stress, Physiological; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water