Study On The Seed Physiological Characteristics And Photosynthetic Physiological Characteristics Of Rare And Endangered Species Stewartia Sinensis

Stewartia sinensis is a perennial deciduous small tree of the family Camellia Theaceae,which is the main representative plant of the genus Stewartia.Most of the genus species are endangered plants.In order to understand the endangered cause of this species,the photosynthetic characteristics,chlorophyll fluorescence characteristics and leaf morphological indexes and relative chlorophyll content of Stewartia sinensis populations under different natural conditions were analyzed.At the same time,under the controlled conditions,the research on artificial sowing and propagation of Stewartia sinensis seeds was carried out.The results are as follows:1.There were significant differences in the morphological indexes of length,width,thickness and 1000-grain weight of the two different provenances(P<0.05).It shows that there is a certain genetic variability between the seeds of Stewartia sinensis from different provenances.The shape of Stewartia sinensis seed is small,which is beneficial to obtain more niche in the interspecific competition.Stewartia sinensis seed has good water absorption and air permeability.The viability of sealed storage seeds in glass bottles is higher than that in flower pots.After low temperature stratification,the seeds partially germinated,indicating that Stewartia sinensis seeds have dormancy,and the seed coat permeability is not the main factor affecting seed dormancy.500mg·L-1 of gibberellin soaked in two storage methods of Stewartia sinensis seeds,the shortest germination time and the highest germination rate in glass bottles.2.Using Li-6400 portable photosynthetic tester,the light response process of three different diameters of Stewartia sinensis under the canopy of the community can be determined.The order of net photosynthetic rate(P_n)changes is:matured tree>seedling>medium tree.The light compensation point and light saturation point of the three kinds of diameter Stewartia sinensis did not change much,indicating that Stewartia sinensis has a small light ecological width.The measured data is fitted with four kinds of mathematical models.It is found that the non-orthogonal hyperbolic model has the highest fitting accuracy for LCP,and the right-angle hyperbolic modified model has the highest fitting accuracy for LSP.3.The diurnal process changes of photosynthetic reaction were determined.It was found that the daily photosynthetic rate of Stewartia sinensis saplings showed a“double peak”curve,reaching the first peak at 12:00 and the second peak at 16:00,with obvious“noon break”phenomenon.The main factor for analyzing the"noon break"is the stomatal limitation factor;Stewartia sinensis is a narrow“single peak left”curve,the main hole is limited by 10:00-16:00 and the non-stomatal is limited Effects of the action.after 16:00.4.The leaf morphological indexes of different diameter grades were significantly different.The leaf length,leaf width and specific leaf area of the leaf morphological indexes of medium trees were significantly higher than saplings and matured trees(P<0.05),indicating that the Stewartia sinensis would change their leaf morphology.To adapt to the low light environment under the forest.5.The chlorophyll fluorescence intensity of saplings was the highest,and the high temperature and strong light stress was the highest.,With the weakening of ambient light intensity,Stewartia sinensis are weakened by increasing the density of the reaction center,the maximum photochemical efficiency after dark reaction,the electron transfer efficiency and the performance index,reducing the quantum ratio of the electron transfer quantum yield and heat dissipation,and the specific activity parameters.6.The relative chlorophyll content of the leaves of the Stewartia sinensis was determined by the comparison of different parts of the tree,medium tree and sapling:leaf tip<leaf<leaf base.It indicated that the relative chlorophyll content of the leaves was related to the maturity of the leaves.In low light conditions,leaves increase chlorophyll content and enhance their ability to capture light energy.