Study On Responses Of Leaf Functional Traits Of Three Medicinal Plants To Water And Nutrients In Karst Area

In the humid karst area of southwest China,because of unreasonable exploitation conditions,vegetation destruction,soil erosion,rocky desertification are serious,resulting in gradually exposed rocks,and the habitat is characterized by soil shortage,less water and discontinuous soil,etc.Land productivity is declining and people are living in poverty.In this paper,three common medicinal plants in Guizhou were used to study the response of medicinal plants to the characteristics of the rocky desertification area.The purpose of this study was to screen out the medicinal plants adapted to the rocky desertification area for the restoration of vegetation and realize the win-win of ecology and economy.Herbaceous plants can cover the ground to prevent the deterioration of rocky desertification in a short period of time.Most vines can use the limited soil and water resources,growth space and light resources of rocky desertification karst mountains,which are ideal plant materials for ecological reconstruction of rocky desertification mountain areas.In this study,common herbaceous plants Imperata Cylindrica,Pueraria lobata and Akebia trifoliata in karst area were studied.Through simulating the characteristics of rocky desertification habitat,pot experiment was carried out in a ventilated greenhouse.Water control experiment（the control group was set up as CK（1d）,Drought time was repeated for 3,4,6,and 8d cycles,and there were 5 groups of experiments with 6 replicates in each group）and N,P addition experiment（Control group N0P0,N1P1,N1P2,N1P3,N2P1,N2P2,N2P3,N3P1,N3P2,N3P3,10 experiments in total,6 replicates in each group）were set up.Respectively from three kinds of morphological characters of plant leaves,anatomical characters,photosynthetic physiological character and leaf C,N,P,K changes in several aspects to study different moisture and nutrient response,dealing with three kinds of plant leaves traits in order to provide reference basis for the heterogeneity of karst stony desert habitat vegetation restoration.The results are as follows:（1）Relationship between Water treatment and Anatomical functional characteristics ofleaves:with the extension of drought stress time（3,4,6,and 8d）,the thickness of the cuticle of three plants increased as follows:the thickness of the cuticle of the leaves of Festuca arundinacea was 2.15 to 3.82μm,Akebia trifoliata was 1.90 to 3.63μm,Pueraria lobata was 1.15 to 1.98μm.the thickness of the sponge tissue（54.56 to 34.63μm;31.88to 37.58μm）and palisade tissue（69.26 to 41.77μm;38.07 to 28.54μm）of Akebia trifoliata and Pueraria lobata decreased with the prolongation of the drought time.The palisade tissue and the sponge tissue were compact from loosely,which were all adaptable changes to the drought.（2）Water use efficiency:with the extension of drought stress time,the water use efficiency of Imperata cylindrica(1.67 mmol·mol^-1?6.87 mmol·mol^-1)and Akebia trifoliata(2.67 mmol·mol^-1?7.09 mmol·mol^-1)increased,but the water use efficiency of Pueraria lobata(3.38 mmol·mol^-1?1.28 mmol·mol^-1)was opposite,and the water efficiency was higher under the condition of sufficient water.（3）The distribution of three medicinal plants in suitable areas:according to the wilting time and soil wilting coefficient of the three species in summer,Akebia trifoliata can be planted in the whole province because of its highest drought tolerance,followed by the drought tolerance of Imperata cylindrica except for the east and southeast of Zunyi.It can be planted in the northwest of Guiyang.The drought tolerance of Pueraria lobata is the worst,except the Middle,East and south of Luodian,southwest of Panxian,Liupanshui,and northwest of Bijie,which are most suitable for distribution in southwestern Guizhou Province,Qiandongnan,Kaili,Majiang,Danzhai,Lei Shan,Taijiang,and Qianxi,Bijie.Through the comprehensive evaluation of drought tolerance,the drought tolerance of three kinds of plants was obtained:Akebia trifoliata>Imperata cylindrica>Pueraria lobata.Therefore,Akebia trifoliata can be planted in areas with relatively poor water conditions,while Pueraria lobata needs to be planted in areas with better water conditions.The Imperata cylindrica is in the middle.（4）From the effects of N,P and N,P interactions on the leaf traits of three plants,the effect of P addition was minimal,and the effect of N addition was the greatest.The interaction effects of N and P were greater than P addition,but the effect was not good.So in the karst area,it is not considered to add P to plants.The effect of N,P addition on morphological characters,photosynthetic characters and leaf element contents of Akebia trifoliata was the least,and the effect on Pueraria lobata was the biggest,and it was more sensitive to the addition of N,P,which indicated that the sensitivity of Akebia trifoliata to environmental factors was relatively weak.It can better adapt to the environment,followed by Imperata cylindrica,Pueraria lobata adaptation to the environment is the weakest.（5）The responses of the three plants to N addition are as follows:Akebia trifoliata>Imperata cylindrica>Pueraria lobata,but they are not sensitive to P response.The N content of the soil used in our experiment is 1.22±0.12 g/kg,in similar soil environment,the highest comprehensive mass of Imperata cylindrica and Pueraria lobata at the middle N level（150 mg/kg）was the most suitable for plant addition,the effects of various traits were the best and the comprehensive quality was the highest.Because of shallow soil layer,high gravel content,barren soil nutrient,water shortage and light shortage in karst rocky desertification area,the growth of plants is restricted.According to the changes and responses of leaves of three plants to water and nutrient,Akebia trifoliata could be considered as a better restoration plant of rocky desertification,followed by Imperata cylindrica,and the worst was Pueraria lobata.It is of great theoretical and practical significance to develop suitable and high water use efficiency screening in rocky desertification area.