| The karst soil with carbonate rock as background has two main characteristics of aridity and high calcium.Handeliodendron bodinieri（Levl.）Rehd is a unique plant in this area and has high medicinal development value.However,the mechanism of H.bodinieri adaptation to arid and high calcium soil is scarce.In order to reveal the characteristics of the effect of exogenous calcium on the resistance of H.bodinieri to drought resistance,in this paper,annual seedlings were used as experimental materials,and 10%PEG-6000 was used to simulate moderate drought,and the effects of different concentrations of exogenous calcium on the physiological and biochemical indexes of H.bodinieri seedlings under drought stress were studied.The research results are as follows:（1）Drought stress resulted in a significant decrease in seedling height,ground diameter and above-ground biomass of H.bodinieri seedlings,a significant increase in underground biomass and root-to-root ratio,and the addition of exogenous calcium significantly increased its seedling height,ground diameter,above-ground biomass,Underground biomass and root-to-root ratio maintain their growth status.（2）Drought stress significantly reduced the net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance（Gs）,water use efficiency（WUE）of the leaves of H.bodinieri seedlings,initial fluorescence（Fo）and non-photochemical quenching coefficient（q P）significantly increased,as well as maximum fluorescence（Fm）,primary light energy conversion efficiency（Fv/Fm）,potential activity of PSⅡ（Fv/Fo）,electron transfer rate（ETR）,PSⅡphotochemical quantum efficiency（ΦPSII）,and The photochemical quenching coefficient（q N）was significantly reduced,and the treatment of different concentrations of exogenous calcium significantly increased the leaf Pn,Tr,Gs,WUE,Fm,Fv/Fm,Fv/Fo,ETR,ΦPSII,and q N,reduced Fo and q P of H.bodinieri seedlings under drought stress.Increased its photosynthetic capacity.（3）Drought stress significantly reduced the relative water content（RWC）and water potential（WP）of the leaves of H.bodinieri seedlings.Exogenous calcium at different concentrations significantly increased RWC and WP and improved their water status.（4）Drought stress increased the content of soluble sugar,free proline and betaine in H.bodinieri seedlings,and treatment with different concentrations of exogenous calcium further promoted the accumulation of osmotic adjustment substances.（5）Drought stress increased the production rate of H2O2 and O2-and the content of MDA in the H.bodinieri seedlings,increased the activities of SOD,POD,and CAT,and inhibited the activities of APX,GPX,and GR.Exogenous calcium treatment significantly reduced the H2O2and O2-production rate and MDA content of H.bodinieri under drought stress,increased the activities of SOD,POD,CAT,APX,GPX and GR,and reduced drought-induced oxidative stress.（6）Principal component analysis found that exogenous calcium improves the drought resistance of H.bodinieri seedlings under drought stress mainly by improving its water status,photosynthetic capacity and antioxidant system.Through membership function analysis,it was found that 10 mmol·L-1Ca Cl2 treatment had the best effect on improving the drought resistance of H.bodinieri under drought stress.To sum up,exogenous calcium mainly improves the drought resistance of H.bodinieri seedlings under drought stress by improving the water status,photosynthetic capacity and antioxidant system,and ultimately maintains the growth status of H.bodinieri under drought conditions,of which 10 mmol·L-1Ca Cl2 treatment has the best effect.This paper reveals the adaptation mechanism of H.bodinieri under drought and high calcium karst habitat from a physiological and biochemical point of view,provides a scientific basis for the screening of suitable tree species in the process of vegetation restoration in karst areas.At the same time,provides drought-resistant breeding and cultivation of H.bodinieri and theoretical guidance for management and medicinal value development. |
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