Comparison For Cytology Of Floral Buds From Various Diploidies Of Apples

Maluspwnila cv. Fuji (2n), Maluspionila cv. Jonagold (3n) and Malus xiaojinensis Cheng et Jiang (4n) of apple were used as the materials in the experiment.Floral buds of different differentiation stages were collected, and tissue structure, cell ultramicro structure and the content of genetic substances in different ploids of apples have been compared.The main results were as follows:This study showed that the differentiation processes of floral buds of different ploids in apples were almost the same, the basic structures of which didn't have obvious differences, but only the polyploid cells were comparatively gigantic and sparse in permutation. Through measuring the diameters of the cells and cytoblasts, it was found that whether in the initial differentiation stage or the sepal stage, the diameters of cells and cytoblasts of triploid Jonagold were obviously longer than those of the diploid ones; similarily, those of the tetraploid Xiaojinensis were obviously longer than those of the triploid and the diploid. The above facts proved that the dimensions of the cells and cytoblasts of the bud tissues had close relations with their ploidy.During the differentiation processes of floral buds,the changes of cell ultramicro structure were the same among the different ploids in apples,including the improvement of cell organelles,the changes of the number of all kinds of cell organelles and the accumulation of nutrition.The cell ultrastucture was compared among the floral buds of different ploids in apples in the same differentiational stages. Compared with the diploid, the polyploid had more cellular organs, especially mitochondria, plastids and golgies, moreover its endoplasmic reticulums and plasmodesma were well developed. Particularly, the mitochondrion cristae of the tetraploid were not abundant, some of which were hollow; the plastids of that were damaged in different degrees and stained lightly, whose lamellae were sparse; some stromata of that appeared netlike; the internal membranes of that were indistinct and with hollow; the heterochromatin in cytoblast area of that were relatively abundant and aggregated into blocks on the verge of the cytoblast membrane. But, the plastids of the triploid were congested with starch grains; the plastids, mitochondria, golgi bodies and endoplasmic reticulums of the triploid were abundant; the plasmodesma of that were more developed than that of the diploid; and the mitochondrion cristae of that were also relatively developed.The content of nucleic acids of the floral buds of the different ploids in apples were comparedduring the differentiation processes dynamic changes of nucleic acid of the floral buds of the ployploids in apples were almost the same as that of diploid. But at the same differentiational stage, the contents of DNA, RNA and the total nucleic acids were obviously improved in the foral buds of polyploids of apples.Compared with the diploid,the numerical value of RNA/DNA of floral buds of triploid was increased.but the extent of increasement was very small, whereas the numerical value of RNA/DNA of floral buds of tetraploid was decreased obviously.