Two models with a master circle and without the master circle for endoduplication and separation of mitochondrial(mt)DNA in higher plants are discussed. In these models, mitochondrial DNAs are actively synthesized in mitochondria in meristematic cells while during cell differentiation, mitochondria divide inabsence of DNA synthesis.Finally, in cells of differentiated tissues such as a root cap and an elongation zone, mitochondria contain a smaller amount of DNA than the genome size and their molecules in each mitochondrion are heterogeneous.

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During sporogenesis, the spore capsule of the bryophyte, Plagiomnium trichomanes, grows to about 4.0mm in length. A relation was observed between developmental stages of spores and spore capsule length on sporogenesis in this bryophyte.

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A tree shape could be considered to form through repetition of an elementary process, that is, branching. When the elementary process is geometrically defined, a tree-like shape is able to be constructed with the aid of digital computers. Some of the artificial trees are made under assumptions of branching geometries(Honda, 1971; Aono and Kunii, 1984; Okumura and Ogawa, 1986, 1988). These artificial trees, however, would not almost contribute to studies of plant morphology, taxonomy and evolution, because investigations of branching geometry of an actual tree are quite insufficient to identify individual species in computer simulations. A study of actual trees has been performed by defining simple bifurcated branch geometries through actual observation(Honda and Fisher, 1978; Honda, Fisher and Tomlinson, 1982). Furthermore, instead of the bifurcation, we have started studies of five-forking branching on the basis of the observation of branching style in Cornus kousa Buerg. ex Hance, keeping in mind of carrying out an advanced study including other species of Cornus, in future. Here, we describe the branching types of C. kousa in detail in Part I of the present paper. In the next paper, Part II will include unified geometrical models of these branch types, and computer simulations based on the models. Eight different branching types were recognized in elongation of new shoots from a winter bud of C. kousa(Figs. 3 and 4). Type A was found in orthotropic shoots and five-forked in monopodial branching. Types B, C, D1 and D2 were found in plagiotropic shoots forming sympodial branching. Type E did not produce an elongated shoot except for a short shoot. Types F1 and F2 appered in flower phase. Total length of annual elongation of shoots of eight types was in the order of their magnitude, A, B, C, F2, D2, D1, F1 and E. During the developmental process, different types played a major role respectively in the shoot formation of a tree at different age. A transition of the “gleading”types proceeded in the following order with an increase of age: A; A, B, C; D1, D2, F2; E, F1. The transition stage of branch types was also recognized among parts of a50-years-old tree. Types B and C were major in the branches at the lower part of the crown, types D1 and D2 were at the middle part, and Types E and F1 were at the upper part. The eight branch types were all found to keep consistently decussate phyllotaxis in shoot formation. Based on the observation of remaining shoots and scars of fallen leaves, a whole crown was reconstituted by connecting eight types of branching(Fig.7).

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Polyethylene glycol embedding is an useful method for immunofluorescence microscopy of plant tissues. The dehydration, infiltration and embedding of materials into the polyethylene glycol is easier than the procedures in the usual paraffin method. And the sectioning is easier than cryosectioning. Serial sections of 5-10μm thickness are obtained with a rotary microtome for various tissues of higher plants. This method is useful for immunofluorescence microscopy of microtubules. Microtubule arrangements in elate formation of Equisetum spore are observed by this method.

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An ordinary paraffin section method has been generally used for a variety of anatomical and histological studies of vascular plants. Recently, however, a semithin section method, which was originally developed for transmission electron microscopy, has been widely applied because of clearness of figures obtained. Materials embedded in Spurr's low-viscosity resin are cut at a thickness of 1-2μm, stained with toluidine blue 0, and observed under a light microscope. The procedures of the semithin section method I employed for a morphogenetic study of Selaginella rhizophores are reported here. Another section method using water-miscible methacrylate(Technovit 7100)is also useful for sectioning of relatively large materials. These methods were useful in recent anatomical studies of Selaginella rhizophores and leguminous seed coats.

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The new embedding resin, Technovit 7100 was applied for some cytochemical methods. The joint use of a 4'-6-diamino-2-phenylindole(DAPI)showed the existence of the small amount of DNA in the cytoplasm in the thin sections and some applications of these methods for research of the embryoiogy in higher plants were shown.

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Euglena gracilis Z cells were synchronized under photoautotrophic conditions using 14h light: 10h dark regimen. The cells sampled in the middle the growth phase of the cell cycle, after 10hr in the light, were serially sectioned for immunoelectron microscopy. Sections were labelled with antibody raised against Euglena light harvesting chlorophyll apoprotein (LHCP II)followed by protein A-gold. Computer aided reconstruction of three-dimensional models revealed spatial distribution of LHCP II in the early growth phase of the cell cycle, and confirmed that LHCP II was highly concentrated over the Golgi apparatus and chloroplast membranes in Euglena.

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