中文摘要：

以MT-1象草（Pennisetum purpureumcv.MT-1）及其近缘品种为研究对象,通过在2008年3月、5月、7月、8月、10月和12月的6次取样,对其茎秆的苯丙氨酸解氨酶（PAL）和4-香豆酸：辅酶A连接酶（4CL）的酶活性动态变化规律进行研究,从而为MT-1象草新品种的推出提供帮助。结果表明：MT-1、N51、Mott和Guimu No.1象草茎秆PAL酶活性的最大值均出现在7月,Huanan象草PAL酶活性的最大值出现在5月,这与它们木质素含量的快速增长期相吻合;最小值出现的月份各不相同,又反映了品种间的差异。5个品种（系）茎秆4CL活性在5月份达到最大值,出现在木质素含量快速增长的前期（快速拔节的前期）;从7月开始大幅度降低,其中MT-1、N51、Huanan和Guimu No.1象草在10月又出现一个小的峰值;Mott象草则在12月又出现一个差异不显著的小高峰,这与其延迟的成熟期密切相关。

英文摘要：

Elephantgrass（Pennisetum purpureum）is an integral component as perennial herbaceous plant in tropical and subtropical regions.Its advantages include high yield,strong regeneration ability,excellent resistance,high nutritional value and the wide range of applications,etc.In this study,five elephantgrass cultivars,sampled in March,May,July,August,October and December in 2008,were tested to determine the dynamic changes of enzyme activities of phenylananine ammonia-lyase（PAL） and 4-coumarate：CoA ligase（4CL） in stems.Results indicate that the PAL maximum activities of four cultivars（＇MT-1＇,＇N51＇,＇Mott＇ and ＇Guimu No.1＇） appeared in July,while ＇Huanan＇ peaked in May.The maximums were consistent with their fast increasing stages of stem lignin content.PAL minimum activities were in different months for different cultivars,showing the differentiations among these five cultivars.The maximum activities of 4CL for the five cultivars were in May,and sharply decreased in July,but with a little activity peak values appeared in October for ＇MT-1＇,＇N51＇,＇Huanan＇ and ＇Guimu No.1＇.＇Mott＇,had no peak value in October,but a non-significant peak value in December due to the delaying maturity stage.The maximums of 4CL appeared generally before the fast lignin content incre,which also was the prophase of fast jointing stage.These research findings can provide important helps for the breeding and extension of ＇MT-1＇ new cultivar.