Study On Hydraulic Characteristics Of Cunninghamia Lanceolata Seedlings And Their Response To Drought

Plant hydraulic imbalance is the key mechanism of drought-induced tree death.The uneven distribution of rainfall caused by rising global temperatures over the past 50 years will result in severe or worse damage to plants in most regions.The severe fluctuation of water conditions in the subtropical monsoon climate region exacerbates the death and succession of plants in the dry season.Therefore,it is a key step to study the mechanism of plant death to reveal the physiological response of trees to plant water stress.In this study,Cunninghamia lanceolata seedlings,a typical tree species in the subtropical monsoon climate area,were selected as experimental objects.Through indoor soil moisture control experiments,the hydraulic characteristics(including structural and functional traits)of seedlings and their responses to water stress were studied.The dynamic characteristics of physiological and ecological characters of leaves and stems of fir seedlings under water stress were analyzed,and the vulnerability curves of 1-year-old fir seedlings leaves and branches under different water conditions were drawn(SWC 31.4～19.7 m3/m3、19.7～12.5 m3/m3、12.5～10.5 m3/m3).To explore the internal rule of water transport and drought tolerance mechanism of seedlings.It provides data and theory support for sustainable development and management of seedlings plantation in subtropical monsoon climate area.The main results are as follows:(1)Under the condition of drought coercion,obtained analysis through the fusion fragility curve of the fir seedlings and branches of the fir seedlings and branches.At different drought stages,the P50 values of drought resistance corresponding to the vulnerability of the leaves and branches of embolism are different,that is,the middle stage of drought coercion(7-14d)The P50 value is the minimum,and the P50 values of the leaves and branches are-2.042MPa and-1.967MPa,followed by the late stages of drought coercion(14-21d),The early stress(0-7d)P50 value is the largest,and the P50 values of the leaves and branches are-1.466MPa and-1.628MPa,respectively.The lower the value of the P50 corresponding to the water potential,the smaller the vulnerability of its embolism,the stronger the drought resistance,and the stronger the anti-thrombosis ability.It shows that in the middle of the drought coercion(7-14d),the effective threshold(θc)of soil moisture is 19.7～12.5 m3/m3,and the fir seedlings have a drought resistance performance,and the branches are stronger than the leaves.(2)Through the correlation analysis of the correlation of the correlation of the correlation between the fir firing leaf ratio(KSL)and the lobe purse resistance(P50leaf),the water guide rate(Kss)and the stem wood part embolism(P50stem),and found the leaves of the leaves There is a significant negative correlation between KSL and P50leaf(R2=0.63,P<0.05),and there is a weak negative correlation between the branches Kss and P50Stem(R2=0.59,P<0.05),indicating that both slices and branches are both There is a weighing relationship between "hydropower efficiencyhydraulic safety".(3)According to correlation and redundant analysis,it is found that there is a certain connection between the structural traits and functional traits of the fir seedlings-branches.Among the contribution rate,the material content(LDMC)of dry leaves is 45.6%;followed by the leaf area(SLA),33.8%;the minimum contribution rate of the heavier(LMA)is 23%.In the contribution rate of branches functional comparison of edge material guide(Kss)and stem wood,the contribution rate of embolism(P50stem),the contribution rate of the catheter diameter(D)is 49.1%;followed by wood density(WD),and the contribution rate is the contribution rate is the contribution rate is the contribution rate is the contribution rate 33.7%;the contribution rate of stems of stems(TDMC)is the minimum,with 28.5%.Among them,the contribution rate of duct diameter to hydraulic structural patterns is the most prominent,indicating that fir can increase the water transmission efficiency by increasing the diameter of the catheter,thereby avoiding the decline in water potential and effectively reducing its potential embolism risk.(4)Because the leaves are more sensitive than the response of the branches,this article has further studied the pores(Gs)and steaming rate(Tr)of the blades.When SWC is lower than 20 m3/m3,Gs will quickly decrease with water coercion.Because Gs affects the size of the cymbal,the pores have the same trend of regulatory effects on photosynthesis and transpiration,and both Gs and Tr show a positive correlation.Growing at 19.7～12.5m3/m3,by regulating Gs to reduce SWC,to slow down the impact of water reduction and coercion on the adverse effects of plants.This series of changes is related to the limitation of the pores of the plant,indicating that the fir will turn off the pores by closing the pores,that is,the use of restrictions to reduce the photosynthetic effects to reduce the amount of water evaporation,so as to slow the water loss of the wood parts of the plant branches.Plants are favorable.In conclusion,this study reveals the close relationship between hydraulic structural and functional traits of leaves and branches of Cunninghamia lanceolata seedlings.Cunninghamia lanceolata leaves are more susceptible to the influence of water conditions than branches,and it is easier to mitigate the effects of drought by changing hydraulic characteristics and using the tradeoff and compensation relationship among various characters.It deepens our understanding of plant hydraulic characteristics and water transport characteristics,and enriches our cognition of various hydraulic systems.