A method of how to grasp branching tree shapes Collaboration of morphology and geometry in the study of Cornus-- I. An approach from tree morphology

• Published in: PLANT MORPHOLOGY Vol. 3; no. 1; pp. 13 - 29
• Main Authors: HATTA, Hiroaki, HONDA, Hisao
• Format: Journal Article
• Language: English
• Published: The Japanese Society of Plant Morphology 1991
• Subjects: Branching types; Computer simulation; Cornus; Geometry; Tree shape
• ISSN: 0918-9726; 1884-4154
• DOI: 10.5685/plmorphol.3.13

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).