Study On Anatomical Characteristics And Ecological Characteristics Of The Wild Plant With Extremely Small Population Cystoathyrium Chinense

Cystoathyrium chinense is a national I level protected plant,only distributed in the area from Yuanyangyan to Tuanniuping,Erlang Mountain,Tianquan County,Sichuan Province.It is rare and in an extremely endangered state.This study takes the naturally distributed C.chinense as the research object,studying its population structure,morphological characteristics,anatomical structure and photosynthesis,in order to understand the endangered system of C.chinenses and provide theoretical support for the protection and recovery of the population.The main research results are as follows.(1)The important value and niche breadth of C.chinense are relatively large.The important value of the right bank population is 26.62,and that of the left bank population is35.77;the niche breadth of the right bank population is 0.80,and that of the left bank population is 0.84,indicating a strong adaptive capacity to environment of this species.At the same time,the niche similarity ratio and niche overlap index of C.chinense and other species are large,and there is strong competition among the populations.(2)There are different age structures in the two populations of C.chinense.The proportions of the right bank population in each age stage are 58.2%for the young age,27.6%for the middle age and 14.2%for the old age,and it belongs to an increasing type.The proportions of the left bank population are 26.2%for the young age,54.8%for the middle age and 19.0%for the old age,which belongs to a recession type.(3)The spatial distribution characteristics of the two populations of C.chinense.are significantly different.The distribution pattern of the right bank population is cluster distribution,while that of the left bank population is between cluster distribution and random distribution.The survival curves of both the populations are in line with the survival curve of Deevey-II type,and the population dynamic characteristics are characterized by a decrease in the early stage,stability in the middle stage and a decline in the later stage.(4)There is a remarkable correlation between the age of C.chinense plant and the various traits of its part above ground.The morphological indicators such as leaf length and blade log number obviously increase with age.The results show that the method of judging the age of C.chinense by the number of petiole residues is feasible.(5)With stomata only in the lower epidermis,the upper and lower epidermal cells of C.chinense are irregularly shaped,and the vertical wall is deep-wavy.The anatomical structure of the leaf is simple,consisting of upper epidermis,lower epidermis,and mesophyll tissue.There is no differentiation of palisade tissue and sponge tissue.The base of the petiole has two split central pillars,arranged in an"eight(in Chinese)"shape.The vascular bundles are all perianal,and the two ends of the xylem have obvious hooks,which are typical"hippocampus".(6)There is a new propagation method for C.chinense--bulblets propagation.The propagules grow on the leaf veins at the tip of the feather blades,similar to the sporangia,with smooth appearance of water droplets.They appear and grow together with the sporangia in mid-May,maturing in the end of August.Most of the bulblets fall off before the leaves turn yellow,and only a few bulblets do not fall off and even grow roots on the leaves.(7)The diurnal variation of net photosynthetic rate(Pn)of C.chinense shows a"single peak"curve,and the peak appears at 10:00.The daily variation of intercellular CO₂concentration(Ci)shows a"V"curve,and the valley value appears at 10:00.The diurnal variations of stomatal conductance(Gs)and transpiration rate(Tr)show a"W"curve,and the peaks appear at 8:00,12:00 and 18:00,with 12:00 being the highest.(8)The maximum net photosynthetic rate of C.chinense is 1.96±0.5?mol·m^-2·s^-1,and the apparent quantum efficiency(AQY)is 0.055±0.008,which is lower than other ferns in the same habitat.The light saturation point is 693.66±16.37?mol·m^-2·s^-1,the light compensation point 6.98±1.06?mol·m^-2·s^-1,and the light adaptation interval is narrow.The results show that the photosynthetic ability of C.chinense is weak,and in a humid and weak-light environment,C.chinense does not have any competitive advantages.To sum up,the main reasons for C.chinense endangerment are high competition among species,low photosynthetic capacity,special habitat.In order to protect the plants and habitats of C.chinense better,it is suggested that the locations of C.chinense should be included in the Labahe Nature Reserve to strengthen local protection,growth monitoring and management protection.At the same time,we should deepen the study of artificial propagation of C.chinense,especially the propagation of bulbils to expand quantity of the population.