Eco-Morphological Investigations on Tiller Development and Rhizome Formation in Kentucky Bluegrass (Poa pratensis L.) for the Higher Yielding and Better Grazing Performance in Japan.

1995年和1996年研究了模拟肯塔基蓝草（KBG）在塑料容器中蛭石培养，每隔2周和4周落叶一次的生长和分蘖种群动态。同时还观察了KBG植株分蘖和根茎的发育形态。(1) 1995年7月移栽后，KBG植株很快就开始大量分蘖，并继续产生新的分蘖，直到9月初第一次落叶，分蘖密度达到约7000 /m^2。然后，分蘖几乎完全停止，可能是由于达到密集的种群和温暖的温度导致活跃的顶端生长。11月进入休眠状态，温度降低，日长缩短，KBG植株再次开始分蘖，冬季分蘖数继续增加，最终在次年第一次收获时分蘖数接近3万片/m^2。但是，密集分蘖种群在春季至初夏生长期逐渐减少，然后在持续50天左右的炎热夏季急剧减少。1996年秋季，匍匐根茎反地向性转向产生的茎顶和冠层分蘖活跃，分蘖数迅速恢复。(2) 1996年刈割4周和2周的总干物质产量均相当丰富，各累积约为0.2400 g。DM/m^2和1600g。DM/m^2牧草。频繁落叶的KBG叶片之所以具有较高的产量水平，主要是因为分蘖群体密集，每个分蘖的叶片形成速度更快（约7天/片）。(3)生长分蘖上的第n个叶片（按倒序编号）与母枝第n-2个叶片所对应的连续分蘖的第1个叶片具有明显的同步性。不能作为常规分蘖伸长的分蘖芽处于休眠状态，部分分蘖芽转向形成根茎状茎尖，并以水平生长方式萌发，主要生长在气蘖基部。这些根状茎发育15 ~ 20株，根状茎长15 ~ 20 cm后，向上伸长方向，在土壤表面形成气生冠，开始像以前的气生分蘖一样有规律地分蘖。利用这一形态特征，KBG植株可以在整个季节形成密集、稳定的分蘖群体。少

Sward growth and tiller population dynamics of simulated Kentucky bluegrass (KBG) swards which were grown in plastic containers with vermiculite culture and defoliated in 2-week- and 4-week-interval were studied in 1995 and 1996. Developmental morphology of tillers and rhizomes of sampled KBG plants was also observed.(1) KBG plants began to tiller aboundantly soon after the establishment of simulated swards (KBG seedlings were transplanted in July 1995) and continued to generate new tillers until the first defoliation of swards made in early September, when tiller density reached ca.7,000/m^2. Then, the tillering stopped almost completely, probably because of attained dense population and warmer temperatures causing active top growth. Coming into the dormant state in November with lowered temperature and shortened day-length, KBG plants again began to tiller, continued to increase tiller number during the winter, and finally got nearly 30,000 tillers/m^2 at the first harvest in next sp … More ring. However, this dense tiller population gradually declined during the growing period from spring to early summer, and then, they abruptly decreased in hot summer periods which lasted about 50 days. Decreased tiller number was recovered very quickly in autumn of 1996 by active tillering of tops and crown formations which were derived from the anti-geotropic turn of creeping rhizomes.(2) In spite of the heavy growth depression in summer and its infection in autumn growth, the total dry matter yield in 1996 both in 4-week- and 2-week-cut sward was rather rich, each accumulated ca.2400 g.DM/m^2 and 1600 g.DM/m^2 herbage, respectively. This higher yielding level of frequently defoliated KBG swards should be mainly derived from the dense tiller population and the quicker leaf formation (about 7 days/leaf) on each existent tiller.(3) There was a distinct regularity that the appearance of each 'n'th leaf (as numbered acropetally) on growing tiller clearly synchronized with the appearance of first leaf of each successive tiller subtended by the leaf 'n-2' of mother shoot. The tiller bud which failed to elongate as a regular tiller stayd in dormant state, and some of them turned to form rhizomatous shoot apex and sprouted with a horizontal growth, mainly at the base of aerial tillers. These rhizomes changed the elongating direction upwards after the development of 15 to 20 phytomers with 15 to 20 cm rhizome length, and turned into an aerial crown at the soil surface and began to tiller regularly as preceding aerial tillers. With this morphological character, KBG plants might easily form a dense, stable tiller population throughout the seasons. Less