Morphological Study On Chinese Fir Seed

As the exclusive and refined tree of south China,Cunninghamia lanceolata has such features as fast growing,straight wooden texture and fine structure.For its wide distribution and long history of cultivation,Chinese fir is of great economic value.Yet,the Chinese fir ovules may suffer the emergence of abortion due to various factors in the development process.Therefore,this thesis aims at revealing the morphological changes in its development of growth and abortion of Chinese fir ovules.The author selected the fine and consistent female fir ovules,collected the seeds every 5-6 days from late April and observed the whole process of its development.The results confirmed the morphological characteristic of ovule female gametophyte abortion and the fertility of embryo abortion of Chinese fir,which adds the research blank of female gametophyte abortion in early studies.The observation also demonstrates the differences in terms of occurrence,the mode of abortion,internal structure and material change of female gamete abortion and embryo abortion.Detailed finding are presented below:(1)The external morphology of the ovules showed that the embryo ovule of female gametophyte abortion in micropylar end part turned black,and then gradually become black from the top of the ovule,and embryo abortion ovule in the micropylar end is gray brown,while the middle lower part is darker and finally the whole part turned dark brown.As for the prototypical characteristics,the middle part in the female gametophyte showed a shrinkage depression while embryo abortion showed a more severe atrophy of the micropylar end.(2)Female gametophyte abortion occurred in early May when the nucellar tissue began to form the internal structure of the female gametophyte.While the embryo abortion first appeared in the middle of June,and most of the embryo abortion occurred during the embryonic development stage of embryo differentiation.(3)The female gametophyte abortion ovule was as the same as the normal ovules in the same developmental period,and the nucellar pollen inside could germinate,and the pollen tube could continue to extend to the ovule inside.(4)The most significant feature of Chinese fir ovule with female gametophyte abortion was the weak and thin internal nucellus,which failed to form a female gametophyte and couldn’t perform the fertilization activities.Embryo abortion was mainly characterized by the abnormal growth of endosperm cells which occupied the area that should be left to the embryo,and endosperm cells that continued to collapse were eventually disappeared,thus it could not provide adequate nutrition and sufficient development space for embryos,as a result,it caused the embryo dry,leaving only embryonic marks.(5)Astringent matter first appeared in the micropylar end of the ovule in female gametophyte abortion,then it spread downward.For embryo abortion of ovule,astringent matter first appeared in the bottom of the ovule,then spread to the top.(6)For the eventually formed ovules of female gamete abortion,its internal structure was mainly the core tissue and filling material of astringent matter.While for the final ovules of the fir seed that occurred embryonic abortion,its internal part was mainly granular astringent granular fillers.