Abstract
The formation and development pattern of tillers and tiller buds of orchardgrass seedlings, grown under favorable conditions, was investigated anatomically. The results are summarized as follows. 1) Generally, the appearance of leaf n (numbered acropetally) of mother shoot synchronized with that of 1st leaf of tiller Tn-3 which was subtended by leaf n-3, so that most of the tillers appearing in this manner produced "corresponding leaves" at almost constant intervals (Table 2). This phenomenon is supported by Katayama's concept) of tillering systems in cereal crops. 2) In addition to the tillering regularity, it was observed that the corresponding leaves, either expanded or expanding, of different tillers were similar in length to each other as in cereal crops (Table 3). 3) Primordia of corresponding leaves of main shoot and emerged primary tillers were initiated almost simultaneously, and subsequent developments progressed analogously (Table 4, Fig.1, 2, 3). Therefore, the externally visible synchronism in the appearance of any corresponding leaf of each emerged tiller may result from its simultaneous initiation and analogous development occurring at the subapical regions. 4) During the tiller bud development, the initiation of successive leaves at the shoot apices of buds proceeded more quickly than that of emerged tillers (Table 4, Fig.2, 3). 5) After all, the developmental course in tiller bud growth is suposed to be composed of two different morphogenetic phases. The first part defined as the "phase of tiller bud formation" is the process from the initiation of primordial bulge of tiller bud to the completion of bud structure (Fig.1, 2). In this case, the structure of tiller bud bearing its own shoot apex and 3〜4 juvenile leaves is achieved immediately after its subtending leaf "n" has just fully expanded on the mother shoot. The second part of the developmental course starts with rapid elongation of 1st leaf of tiller bud "Tn" being subtended by the leaf "n" and concludes with the tip emergence of the tiller from subtending leaf sheath. This is defined as the "phase of tiller bud elongation".
