牧食损害对伊乐藻(Elodea nuttallii)生长的影响

在室外实验条件下,研究了模拟牧食损害(动物牧食所造成的损害)对伊乐藻植株生长的影响。结果表明:3种人工损害方式(去除植株50%叶片,去除植株顶端,以及同时去除植物顶端与50%叶片)对伊乐藻的生长率、主枝与分枝长度的增长、植物的干物质、氮、磷含量等均有不同程度的影响。其中,去叶与去顶去叶损害显著抑制了伊乐藻的生长,相对生长率分别占未受损植株的62.8%与74.4%;去顶与去顶去叶损害使伊乐藻主枝生长几乎停止,却显著促进了植物分枝的生长;去叶损害对植株的生长率、主枝与分枝长度的生长无明显抑制并却显著地降低了分枝的重量。对受损伊乐藻生长的机理进行了分析,探讨了东太湖伊乐藻现存量近年来迅速增加的原因并认为植物残体是伊乐藻种群扩张的重要因素之一。

Effects of mechanical damage on the growth of Elodea nuttallii

An outdoor experiment was conducted to examine effects of damage on the growth of submerged macrophyte Elodea nuttallii from May to July in 2006. There were three damage treatments: growing tips removed, 50% defoliation and 50% defoliation and growing tips removed. Results showed that three damage treatments affected plant relative growth rate, length of main shoot and lateral shoots, and content of dry mass, nitrogen and phosphorus of plant tissue. Compared with undamaged plant, plant relative growth rate was only 62.8% for 50% defoliation treatment and 74.4% for 50% defoliation and growing tips removed treatment. The main shoot growth of plant in removed growing tips treatment and 50% defoliation and growing tips removed treatment almost stopped, but lateral shoots grew significantly. This study suggests that plant fragments may be responsible for the increasing standing biomass of E. nuttallii in East Taihu Lake in recent years.