Responses of Akebia trifoliate leaf anatomical structure and photosynthetic characteristic to drought stress

ObjectiveThe anatomical structure and photosynthetic characteristics of leaves of Akebia trifoliate were observed and measured under drought stress to provide references for selecting suitable plants for ecological restoration in karst rocky desertification area in southwest China.MethodA. trifoliate,a karst adaptable specie,was taken as material. Through pot experiment and continuous drought stress,seeding leaf anatomical structures were observed by conventional paraffin section,and changes of photosynthetic physiological characteristics were analyzed by measuring photosynthetic parameters with Li-6400. The changes of anatomical structures and photosynthetic characters and the correlation between the two were analyzed.ResultWith soil relative water content(SRWC)decreasing,the thickness of seeding leaf thinned, water content decreased and palisade tissues shortened in the structural features of the leaves of A. trifoliate. Chlorophyll content(Chlt),photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)decreased,water use efficiency (WUE)increased. Most of the anatomical and photosynthetic indicators showed significant difference when SRWC de-creased to 29%(P<0.05). The results of principal component analysis showed that the load values of four principal compo-nents in the characteristic values of leaf anatomy greater than 1.000 varied greatly,with a contribution rate of 88.195%. The main indicators were palisade tissue,lower epidermis,xylem,and spongy tissue. Among these photosynthetic index eigenvalues of leaves which were larger than 1.000,Gs and Chlt were two main components with large differences in load values,with a contribution rate of 83.277%. The correlation analysis showed that there was significant positive correlation between SRWC and leaf water content(LWC),Chlt,Pn,Gs,Ci,Tr,Ls,leaf thickness,palisade tissue thickness and xylem thickness in leaf anatomy(P<0.01,the same below). There was extremely significant negative correlation between WUE and leaf structure loose degree(SR).ConclusionBy changing the structure characteristics,reducing photosynthesis and increasing water use efficiency under drought stress,seedlings of A. trifoliate can adapt to the karst environment in south-west China where drought take place frequently. SRWC of 29% can be regarded as the starting point of drought stress of A. trifoliate seedlings. Palisade tissue,spongy tissue,xylem and G s can be used as reference indexes for the screening of drought-tolerant varieties of A. trifoliate.