Trends of population density of standing tillers, and developmental morphology of stolons and aerial-tillers in Japanese Iawn grass (Zoysia japonica Steud.) growing in sward conditions.

频繁落叶的日本结缕草（Zoysia japonica Steud.）种群的分蘖密度总体上保持在1.5万/m^2左右的较高水平，与日本的假丝草类草地形成鲜明对比，后者在建立后的生长期初始密度往往迅速下降。此外，结缕草即使在频繁落叶的情况下也能实现相对突出的产量。构成上述结缕草密集种群的航分蘖的主体是由匍匐茎各多节的下节大量产生的所谓“Ta”分蘖组成。与此相反，位于Ta分蘖上方一个节点的Tb分蘖的正常出现似乎很罕见，因为大部分（近80%）Tb芽在季节中休眠时间较长。在本研究频繁落叶的情况下，老龄和衰老的Ta和Tb分蘖叶腋上出现的次生和三级分蘖相当自由，占现有分蘖总数的20% ~ 30%。与单株生长相比，匍匐茎多节的形成和伸展生长受到强烈抑制；年平均形成多节数约20个，匍匐茎总伸长约30 cm。在本研究的解剖学研究中，可以清楚地观察到Ta和Tb芽在每个匍匐茎顶端附近的发育有明显的差异。分蘖芽分化始于Ta和Tb分蘖芽，它们都附着在同一个多节上，这似乎是导致Ta和Tb分蘖分化的原因之一。

Standing tiller densities in frequently defoliated Japanese lawn grass (Zoysia japonica Steud.) populations were generally kept at very high level around 15,000/m^2, and revealed quite excellent contrast to those of Festucoid grasslands cultivated in Japan where initial plant densities tend to decrease quickly during actively growing periods after the establishment. Besides, Zoysia swards examined often showed their ability to realize relatively prominent yield even under frequent defoliations.Principal part of aerial-tillers that constructed the above mentioned dense population of Zoysia was composed of so-called Ta tillers which vigorously generated from the lower nodes of every multiple-node of stolons. In contrast with this, regular emergence of Tb tillers which located one node above the Ta tillers seemed to be rare, as a larger part (nearly 80%) of Tb buds stayed dormant for a longer period during the seasons. Under highly frequent defoliations as conducted in the present study, secondary and tertiary tillers appeared rather freely from the leaf axils of aged and senescing Ta and Tb tillers, and so they supplemented 20 to 30% of total existing tillers.The formation of multiple-node and extension growth in each stolon growing under a sward condition was suppressed strongly as compared with those of single-plants ; average number of multiple-nodes formed per year was ca. 20 and total stolon elongation was around 30 cm. In anatomical investigation in this study, a distinct difference of development was clearly observed between Ta and Tb buds near the apex of each stolon. The differential tiller bud initiation commenced in Ta and Tb tiller buds, both attaching to the same multiple-node, seems to be one reason to result the following diverse development of Ta and Tb tillers.