J Integr Plant Biol. ›› 1962, Vol. 10 ›› Issue (4): -.

• Research Articles •    

Morphological and Cytological Observations of the Process of Fertilization of the Wheat

S. Y. Hu   

Abstract: The aim of this study was to follow the dynamics of nucleic acid and polysaccharide, as well as the distribution of mitochondria, based on the morphological observations in the development of the embryo sac and in the process of fertilization in the winter wheat, variety "Early premium". The following results are obtained: 1. The full equipment of the embryo sacegg aparatus, antipodal cells and polar nucleiis attained 6–5 days before flowering. From this time on the female elements and their nuclei gradually increase in size. Until at anthesis, the diameters of fully ma- tured female nuclei are about twice as large as those of newly formed elements. The mature egg cell is highly vacuolated, but it becomes unvacuolated and has dense cytoplasm after fertilization. 2. The fertilization process of wheat is of the premitotic type. 3. During the development of the embryo sac and fertilization, the female nuclei always give a clearly positive Feulgen reaction, which indicates the existence of DNA in their nuclei at any stage. In the mature egg, however, the fine DNA particles are scattered in the enlarged nucleus, that they are visible only with the aid of oil immersion objective. Methyl green-pyronin method also very clearly demonstrates the same condition. 4. The RNA content in the cytoplasm of the egg cell, demonstrated by the intensity of pyronin staining, shows a regularly variation during the development. In young egg cell, being in a juvenile condition, is rich in RNA. content, With the growth of the embryo sac the RNA content of the egg cell gradually shows a transient drop up to fertilization. After fertilization the egg cell is rich in RNA again and presents small pyroninphilic lumps in cytoplasm. These changes in RNA content is correlated with the vacuolation of cytoplasm and probably with physiological state of the egg cell. 5. Starch grains are always present in the cytoplasm of egg cell and zygote, as well as the central cytoplasm of embryo sac during the development of embryo sac and the process of fertilization. In synergids, starch grains have been found only in their early developmental stage, but in antipodal cells starch grains have not been found at any stage. This plastic substance in form of temporary starch grains is a reserve food for further development of the female element of embryo sac. 6. There are mitochondria in the mature male and female gametophyte. The distribution of the mitochondria in the embryo sac before and after fertilization shows no apparent change. In several-celled proembryo stage, the mitochondria of the antipodal cells gradually disappear. 7. The results of this observation support the conception that the embryo sac is a complete physiological system and all the elements of embryo sac contribute to sound development of the egg cell.

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