Researches On Conservation Biology Of Aleuritopteris Squamosa

Aleuritopteris squamosa is a unique endangered plant in China with a narrow natural distribution.The response to water conditions in wild dry habitats shows a desiccation tolerance,and there is currently no research on the criminal crisis system of A.squamosa.In this paper,Pteris nervosa Thunb.,which is widely distributed in China and has different habitat conditions,was used as a control plant.The leaf morphological structure,photosynthetic physiological characteristics and photosynthesis response mechanism of drought and rewatering were studied.A comparative study was conducted to investigate the causes of the habitat limitations of A.squamosa and its crest crisis system,providing a scientific basis for conservation and resource utilization.The results show:(1)There were significant differences in the leaf traits and biomass accumulation and distribution of A.squamosa and P.nervosa.A.squamosa had larger leaf thickness,smaller leaf area and less leaf number per plant.The aboveground biomass and total biomass of A.squamosa were significantly less than that of P.nervosa,and the root-shoot ratio was significantly greater than that of P.nervosa.(2)There was no obvious differentiation of palisade tissue and sponge tissue in the cross-sectional anatomical structure of the leaves of A.squamosa and P.nervosa.The shape and arrangement of mesophyll cells of the two species were irregular,but the arrangement of A.squamosa "was closer,the leaf epidermis is thicker,the main vascular bundle of the leaf is smaller than P.nervosa,and the lower surface of A.squamosa has epidermal hair,which forms an adaptation to drought in the structure of the tissue.(3)The chlorophyll content of A.squamosa is higher than that of P.nervosa,and it has a large maximum net photosynthetic rate and a low light compensation point.It has strong shade tolerance and is more adaptable to the light environment.(4)Drought treatment significantly reduced the net photosynthetic rate of the two species.The photosynthetic rate of A.squamosa was close to 0 when the leaf water content decreased by about 45%,indicating a protective mechanism for early stop photosynthesis.After rewatering,the leaf water content,leaf water potential and gas exchange parameters of A.squamosa returned to the control level or close to the control level.The parameters of P.nervosa can not be restored.(5)During the drought and rewatering process,the photosynthetic apparatus of A.squamosa was relatively intact,and the chlorophyll fluorescence parameters Fv/Fm,Fv/Fo,Yield,ETR and qP did not change significantly.The chlorophyll fluorescence parameters of P.nervosa in the process of drought were significantly reduced,and could not be recovered after rehydration.Under a certain degree of drought stress,both species can dissipate excess light energy in time by increasing NPQ,but NPQ of P.nervosa decreased sharply under extreme drought and the photosynthetic apparatus was destroyed.Although the photosynthetic rate is high and the light adaptability is strong,A.squamosa has a small leaf area,a small number of leaves per plant,and a small total photosynthetic area,so the material accumulation is less.At the same time,its photosynthetic protection mechanism makes it sensitive to water changes,and stops photosynthesis earlier than P.nervosa.This is an ecological adaptation mechanism to the arid environment,which limits its habitat to arid areas.