Studies On The Morphological And Photosynthetic Physiological Characteristics Of The Endemic And Rare Plant Cinnamomum Chago

Cinnamomum chago B.S.Sun et H.L.Zhao is a species of the genus Cinnamomum belongs to the family Lauraceae.This species mainly distributed in the Lancang river upstream tributary mountain in Yunlong and Yangbi county in Yunnan province.It exhibited a very limited distribution and there were no saplings under the adult trees.In the present-study,we observed and compared the morphological anatomy of C.chago and its allied species to reveal the taxonomic position of C.chago and provide the basis for the classification of Cinnamomum.Through shading treatment,we discussed the ecological adaptability of C.chago seedlings to light based on the chlorophyll fluorescence parameters,photosynthetic characteristics and morphological anatomy.Our results provided an important scientific reference for the introduction and cultivation of C.chago.The main findings are as follows:C.chago can be clearly distinguished from its pinnate leaf veins without three veins from base of leaf.The morphological feature of C.chago,opposite leaves to subopposite leaves,no glandular fossa,opposite single flower in branch knot of inflorescence axis,anthers oblong,pollen surface with triangular spinule and the base of the spinule with cushion bumps and cushion bumps without granulation,were similar to Sect.Cinnamomum.Corresponding feature in Sect.Camphora include leaves alternate,vein axils with glandular fossa,2-3 flowers in branch knot of inflorescence axis,anthers short round,cushion bumps with granulation;The staminodes of C.chago without petiole is similar to Sect.Camphora.The stem's primary structure of C,chago and its allied species consists of epidermis,cortex,phloem,xylem and pith.They are secretory cells in the cortex and sclerified parenchyma cells in the pith in all species except C.chago.The leaves of C.chago and its allied species were typical bifacial leaf.In this study,the thickness of the upper epidermal cells is large in the leaves of Sect.Camphora,with 1-2 layers of palisade cells,while the thickness of the upper epidermal cells were small in the leaves of C.chago,Sect.Cinnamomum,with 2 layers of palisade cells.There were oblong and round secretory cells in leaves of C.chago,Sect.Camphora,and oblong secretory cells were only distributed in palisade tissue,while there was no significant difference in distribution area between oval and round secretory cells in Sect.Cinnamomum.The sponge tissues of C.chago were closely,compared with its allied species,the ratio of palisade tissue/sponge tissues is highest in C.chago,which may be related to its long-term adaptation to cold and dry environment.The polygons upper epidermal cells with straight anticlinal wall of C.chago are similar to Sect.Camphora.The C.chago,irregular lower epidermal cells with beaded anticlinal wall,stomatal with non-upset beaded anticlinal wall and only one subsidiary trapped in epidermal cells were similar to Sect.Cinnamomum.Stomata with upset and straight anticlinal wall and two subsidiary were at the same level as epidermal cells.With the increase of shading rate,photosynthetic pigment and SLA increased while LDCM decreased.The results indicated that the light trapping ability of C.chago was increased under low light condition,which reflected the adaptability of C.chago to low light environment.The qP,ETR,?PS II and NPQ of C.chago achieved significant differences between the various treatment.The highest qP,ETR and ?PS ? under the 50%shade rate and the minimum NPQ under 75%shade rate indicated moderate shading can improve the photosynthetic capacity of PSII system and reduce the heat dissipation.The highest NPQ,Fo,the lowest Fv/FO and Ik in full light indicated the photosynthetic system of C.chago's leaves might be inhibited.Moderate shading can increase the Pmax,Gs,Tr and Pn of C.chago's seedlings and increase the carbon assimilation efficiency.The LCP,LSP,Rd,leaf thickness,cuticle thickness,palisade tissue thickness,palisade cell aspect ratio and stomatal density decreased with the increased of shading rate indicated C.chago has certain adaptability to low light environment.In summary,the combined characteristics(Sect.Camphora and Sect.Cinnamomum)of C.chago revealed its primitive classification status.These characteristics,including the leaf vein,inflorescence,anther shape,staminodes,secretory cells,epidermal thickness,epidermal cell morphology and stomatal characteristics were steady difference between the two sections of Cinnamomum.Seedlings of C.chago have a certain adaptability to low-light environment and moderate shading can improve its photosynthetic efficiency.thus,it is speculated that shading under the forest is not the reason restricting the growth of seedlings of C.chago.