草菇單孢子菌絲細胞核之研究

Cytology of Monosporous Hyphae of Volvariella volvacea

由草菇單擔孢子芽生長之菌絲，其細胞內之細胞核是多核性；細胞核之大小形狀及細胞內之位置都不一致。細胞核的分裂軸與菌絲成不平或垂直方向；核分裂包括絲及無絲分裂兩種，細胞內有同時進行此兩程核分裂現象。細胞核分裂後隔膜並不立刻形成，故造成多核現象。細胞核經過菌絲隔膜，由一細胞轉移到另一細胞中；此種細胞核轉移現象初步證明草菇可能是同宗結合。

The hyphae of Volvariella volvacea (Bull. ex Fr.) Sing. used for cytological study were the subcultural mycelium of monosporous progeny. Only aerial hyphae were removed from a mycelial mat and they were stained. Vegetative hyhae of this fungus are filamentous and branching. Septum between adjacent cells is conspicuous. Vegetative hyphal cells are multinucleate. Number of nuclei per cell is various. Some cells have only 3 nuclei, but some may have nuclei as many as 31, the average is about 11 nuclei per cell. Nuclei are not evenly distributed in the cytoplasm. Two size of nuclei are present. One is larger and granular, and the other is smaller and homogenous. The interphase nuclei of mitosis are vary in diameter, about 1.68-2.98μ, either granular or homogenous. The prophase nuclei are larger in size, about 4.2μ in diameter. These nuclei are weak in stainability. Nuclear envolope does not break down during metaphase. The feature that the metaphase chromosomes arrange on the equator plane as in high plants was not observed. Spindle fibers were not obvious. Chromosome number count was impossible for the chromosomes were not distinctly separated. At anaphase, two sets of chromosomes have been completely separated. They lie on the opposite poles leaving a clear interzonal region in between. Telophase nuclei are visualized as two clusters of daughter chromosomes round up and nuclear membranes enclose the two daughter nuclei which are identical in size and shape. The process of amitosis is simple. Without chromosome condensation and rearrangement the nucleus increases in size and elongate. Then the two poles of nucleus starts to constrict and a furrow is formed at the midregion of the elongate nucleus. Eventually, the two image halves are more or less round up and two daughter nuclei are formed. In our materials, both mitosis and amitosis are found. Migrating nucleus is characterized by its unique shape. It consists of a swallen portion and a pointed end, just like a tadpole. The pointed end is the migrating front of the nucleus. The whole nucleus is granular. This provides evidence that the migrating nuclei are the mature interphase nuclei. Migrating nucleus passing from one cell to another through septal pore was observed. When wedged in the septal pore it is dumbbell-shaped which occurs simply as a result of constriction by the septum. The presence of migrating nuclei in the monosporus hyphae suggests the preliminary information that this fungus is homothallic. No centrioles were observed in the migrating nuclei in V. volvacea hyphae of our stained materials. Thus, the mechanism of nuclear motility is uncertain in this fungus.