Measuring Method Selection Of Photosynthesis In Vitro And Photosynthetic Eco-physiological Characteristics Of 6 Kinds Of Rare And Endangered Plants In Qinling Mountains

Qinling mountains are the intersectional area of many floras,where many rare and endangered plants distribute.Photosynthesis has an important influence on plant growth and interspecific competition.Nitrogen tradeoff within photosynthetic apparatus would change photosynthetic capacity of plants.The further study of photosynthetic characteristics and photosynthetic nitrogen allocation strategies of rare and endangered plants in Qinling mountains is beneficial to analyze the endangered mechanism of rare and endangered plants in Qinling mountains.Therefore,this study carried out the following three aspects of work:???Measuring method comparison of photosynthesis in vitro: Aiming at the problem that the value in vitro was sometimes lower than the value in situ after beveling method was used to measure photosynthesis,5 in-vitro methods?beveling,cracking,splitting,girdling,and immersing in salicylic acid solution?for preparing detached tree branches were evaluated to develop a more applicable method for in vitro determination of photosynthesis with 10 common tree species as experimental materials,in-situ photosynthetic measurement as the control.The study could provide a feasible way for the further study of photosynthetic eco-physiological characteristics of tall tree species in mountain area.???Photosynthetic characteristics and photosynthetic nitrogen allocation strategies:Photosynthetic characteristics and photosynthetic nitrogen allocation strategies of Psathyrostachys huashanica,Fagopyrum dibotrys,Cercidiphyllum japonicum,Euptelea pleiospermum,Acer miaotaiense and Tapiscia sinensis were compared with those of their widespread companion species or widespread relative species respectively in order to determine whether there was difference in the photosynthetic characteristics and photosynthetic nitrogen allocation strategy between rare and endangered plants and their control plants,then to explore the possible endangerment and scarcity mechanism of plants from the perspective of photosynthetic nitrogen allocation.???Adaptability study to light environment: Using Tapiscia sinensis,Euptelea pleiospermum and Psathyrostachys huashanica as experimental materials,4treatments were set up: full illumination,light shading,moderate shading and heavy shading.The photosynthetic eco-physiological characteristics of Tapiscia sinensis,Euptelea pleiospermum and Psathyrostachys huashanica under different shading conditions were studied to further clarify their endangered mechanism from the perspective of light environment changing.The main conclusions of this study were as follows:?1?Cracking method was more feasible for in-vitro photosynthesis measurement of trees.After cracking,water absorption area of detached branches increased,the external force of cracking branches would also increase the scouring action of water on colloid fluid remarkably.So cracking proved better among the 5 methods evaluated.This study provides technical support for the accurate measurement of plant functional traits and offers a feasible approach for the further study of photosynthetic eco-physiological characteristics of tall trees in Qinling mountains.?2?Photosynthetic characteristics of Cercidiphyllum japonicum,Euptelea pleiospermum and Acer miaotaiense are different with the photosynthetic characteristics of their widespread species.The available light intensity range,resource utilization capacity(P_max,V_cmax,J_max)as well as resource utilization efficiency?PNUE?of the 3 kinds of plants were lower than those of their comparing plants whether they were saplings or adult trees.?3?Relative defects in nitrogen allocation strategy of Cercidiphyllum japonicum,Euptelea pleiospermum and Acer miaotaiense were important reasons for their endangerment and scarcity.The allocated proportion and quantity of nitrogen in bioenergetic and carboxylation of Cercidiphyllum japonicum,Euptelea pleiospermum and Acer miaotaiense were less than those of their comparing species,the rare and endangered plants allocated less leaf N to photosynthetic apparatus in both sapling stage and adult stage.Relative defects in nitrogen allocation restricted the conversion and utilization of light energy,which made the rare and endangered plants be in arelatively disadvantageous position in the community competition This was an important possible reason for the scarcity of Cercidiphyllum japonicum,Euptelea pleiospermum and Acer miaotaiense.?4?The comparative results of photosynthetic nitrogen allocation strategies also showed differences in different growth stages.In sapling stage,the photosynthetic nitrogen allocation strategy of Tapiscia sinensis showed relative disadvantage?the allocated quantities of nitrogen in bioenergetic and carboxylation less than its comparing specie?;in adult stage,the photosynthetic nitrogen allocation strategy of Tapiscia sinensis had a certain comparative advantages.The relative disadvantage of photosynthetic characteristics and photosynthetic nitrogen allocation of Tapiscia sinensis saplings made Tapiscia sinensis be in a relatively disadvantageous position in community competition,which was an important possible reason for the poor natural regeneration of Tapiscia sinensis.?5?Photosynthetic nitrogen allocation was not the key of the endangered plants,Psathyrostachys huashanica and Fagopyrum dibotrys.There was a certain homoplasy in internal allocation strategy of photosynthetic nitrogen between Psathyrostachys huashanica and Agropyron cristatum.Compared with thereference plant,the photosynthetic nitrogen allocation strategy of Fagopyrum dibotrys has relative advantages.?6?Light conditions could affect photosynthetic nitrogen allocation strategies of rare and endangered plants.With illumination decreasing,Tapiscia sinensis,Euptelea pleiospermum and Psathyrostachys huashanica would gradually increase the fraction of the total leaf nitrogen allocated to light-harvesting components in order to obtain more light energy.Under suitable light conditions,photosynthetic nitrogen allocation strategies of Tapiscia sinensis,Euptelea pleiospermum and Psathyrostachys huashanica would be optimized.Under light shading?shading 25%?,photosynthetic nitrogen allocation strategy of Tapiscia sinensis performed well.Under moderate shading?shading 50%?.the photosynthetic nitrogen allocation strategy of Euptelea pleiospermum was better.Under full illumination,photosynthetic nitrogen allocation of Psathyrostachys huashanica had significant quantitative advantage?p<0.05?.Afterthe optimization and adjustment of photosynthetic nitrogen distribution strategies of rare and endangered plants,the resource utilization capacity and the resource utilization efficiency of plants were further improved,leading to more biomass accumulation finally.On the basis of optimizing the measurement of in-vitro photosynthesis of trees,the endangerment mechanism of 6 rare and endangered plants in Qinling Mountains was explored through the study of photosynthetic eco-physiological characteristics,which provided a strong support for the scientific protection of rare and endangered plants and biodiversity in Qinling area.By studying the photosynthetic eco-physiological characteristics of rare and endangered plants in different light environments,the specific needs of Tapiscia sinensis,Euptelea pleiospermum and Psathyrostachys huashanica for light environment were clarified,which provided technical support for the ex situ conservation and artificial breeding of rare and endangered plants.