4种不同根型树种对干旱胁迫的生理响应差异OACHSSCD

Amid escalating incidences of severe drought episodes driven by global climate change,is essential for forest management and ecological rehabilitation,elucidating the hydraulic and physiological response mechanisms of arboreal species with varying root system architectures.This investigation utilized two-year-old seedlings of two deep-rooted taxa,Camphora officinarum and Quercus variabilis,alongside two shallow-rooted taxa,Cunninghamia lanceolata and Phyllostachys edulis-representative species of subtropical forest ecosystems.A controlled desiccation protocol simulating a 42-day progressive drought stress was applied,with systematic assessment of temporal variations in water potential,chlorophyll fluorescence parameters,osmolyte accumulation,and oxidative stress biomarkers.Key findings indicate that root system architecture underpined divergent drought resistance mechanisms.Deep-rooted species sustained more effective water uptake within constrained soil profiles through extended root systems and elevated root length density,thereby significantly delaying leaf desiccation and chlorophyll degradation.Camphora officinarum exhibited a 22.78％reduction in leaf relative water content(RWC)and an 8.32％decline in Soil and Plant Analyzer Development(SPAD)values,whereas Quercus variabilis showed decreases of 25.86％in RWC and 34.48％in SPAD.Conversely,shallow-rooted species experienced pronounced water and chlorophyll loss:Cunninghamia lanceolata RWC decreased by 70.43％with a 56.04％reduction in SPAD,and Phyllostachys edulis RWC declined by 60.43％.Deep-rooted species demonstrate synergistic drought resistance strategies,including enhanced non-photochemical quenching(NPQ)that mitigates photodamage and prolongs photosystemⅡ stability.During early drought stages,NPQ in Quercus variabilis increased by 170.10％,while Camphora officinarum maintained a rise by 35.38％.Concurrent osmolyte accumulation was observed,with soluble sugars in C.officinarum increasing 2.20-fold and proline in Quercus variabilis rising 46.46-fold,effectively regulating malondialdehyde(MDA)content reaching 211.72％of the initial in Camphora officinarum and decreasing to 52.17％in Quercus variabilis.Redundancy analysis identified soil moisture as a primary driver of these physiological adaptations.Vulnerability assessments revealed that reliance on depletable shallow soil water precipitates rapid deterioration of water status and photosynthetic apparatus,with transient activation of photoprotective mechanisms preceding collapse.Despite osmolyte surges-proline increasing 32.41-fold in Cunninghamia lanceolata and 153.17-fold in Phyllostachys edulis at day 28-severe membrane damage ensued,with MDA content reaching 168.99％and 238.19％of baseline,respectively,indicating physiological failure due to cumulative drought stress.Life-history strategies modulate the response pathways of species with analogous root system architecture:while both species are deep-rooted,Camphora officinarum(evergreen)emphasizes sustained leaf function and carbon assimilation,whereas Quercus variabilis(deciduous)employs programmed senescence to conserve resources for regeneration.In conclusion,root architecture critically influences physiological responses by optimizing water acquisition.Deep-rooted species exhibit superior drought resilience through integrated mechanisms of water conservation,photosystem protection,and osmotic regulation.These insights advocate for the prioritization of deep-rooted native species in ecological restoration efforts within subtropical monsoon regions to bolster forest resilience against extreme drought events.