| Sect.Ghrysantha belongs to Camellia of Theaceae.It has high ornamental value,health care and medicinal value and research value.It is a national key protected plant.Due to the serious human damage and environmental changes,the number of wild yellow camellia has decreased sharply,so it is urgent to protect and study it.The annual stems of of wild species(Nonggang Nature Reserve,Guangxi)and cultivated species(Nanning Golden Camellia Park,Guangxi)of Camellia chrysanthoides,C.impressinervis,C.limonia,C.longgangensis,C.perpetua and C.ptilosperma were used as experimental materials.The anatomical and structural characteristics of young stems of six wild and cultivated yellow camellia species were observed and analyzed by sectioning paraffin blocks,segregation and sectioning,iodine crystallization and X-ray diffraction,so as to provide some theoretical support for the classification,systematic evolution,introduction protection of yellow camellia.The main research results are as follows:(1)The cross-sectional anatomical structures of the annual stems of six kinds of yellow camellia are composed of epidermis,cortex,phloem,cambium,xylem and pith,and crystals appear in phloem and pith.The changes of environmental factors affect the structural characteristics of the six yellow camellia stems,especially the cortical thickness,xylem thickness,xylem rate and pulp rate,which can be used to evaluate the ecological adaptability of yellow camellia stems.(2)There are two types of vessel in the annual stems of six kinds of yellow camellia,the ladder shaped duct and the transition duct from ladder shaped to hole shaped.The end wall of the catheter is basically ladder shaped perforated plate,and a few have mesh ladder shaped mixed perforated plates,and the end wall is inclined.There were differences in the proportion and shape of the caudal end of the vessel molecule in the same kind of yellow camellia in two habitats.The patterns of grooves and holes on the side wall of the conduit are aligned.The wood fibers of six kinds of yellow camellia are fine spun hammer shaped.There is a strong correlation between vessel elements,morphological characteristics of wood fiber and habitat factors.Among them,the length,width,length width ratio of vessel,cavity diameter ratio and wall cavity ratio of wood fiber can represent the main information of vessel elements and wood fiber characteristics of young stem under two growth environments.(3)Based on the cluster analysis of various characters of the anatomical morphological structure of the young stem,the wild species of C.impressinervis,C.longgangensis and C.ptilosperma belong to one group,which shows that the three are closely related.This result shows that the morphological structure characters of the stem can be used as a reference for the classification of yellow camellia.The clustering results of wild species and cultivated species are different,which shows that the classification results based on stem morphological structure are affected by the environment.If cultivated species are used as classification research materials,they should be considered carefully.(4)The interspecific variation range of microfibril angle and crystallinity of xylem of young stem of wild yellow camellia is greater than that of cultivated species,indicating that wild species are greatly affected by the environment.The largest intraspecific variation of microfibril angle was C.chrysanthoides,while the largest intraspecific variation of crystallinity was C.limonia.(5)Although there are some differences in the adaptability of the morphological structure of the stems of six kinds of yellow camellia to the environment,combined with the data records and field observation,it is found that these kinds of yellow camellia have good adaptability to the environment,which is conducive to their introduction,cultivation and ex situ protection;It can also increase the population of yellow camellia by artificial cultivation methods such as cutting and tissue culture,protect germplasm resources. |
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