几种收割策略下轮叶黑藻（Hydrilla verticillata）的生长恢复研究

2005年5月中旬至10月下旬,在水深为24cm的桶中,以水面下6、12、18cm等3个收割强度对轮叶黑藻（Hydrilla verticillata）分别进行了连续4次收割实验,研究收割强度、收割频次对其生长恢复的影响。结果表明,温度相近时,收割强度较高或收割频数增加将延长轮叶黑藻的恢复时间。以18cm强度收割第2次、第3次后,轮叶黑藻需近2个月的时间恢复;以12cm强度第3次收割后,需43d恢复;其余各次收割后,轮叶黑藻均在1个月内恢复。8月下旬,以18cm强度收割第3次后,普通枝条及匍匐枝的数目与总长明显减少,从而抑制了轮叶黑藻以匍匐枝和冬芽进行无性繁殖。其他各次收割均处于轮叶黑藻旺盛生长的季节,收割后,普通枝条和匍匐枝的数目和总长明显增加,将不会抑制植物的无性繁殖。各次收割后至少75%的新生枝条从基部萌生,这些枝条成为生长最为旺盛的部分。在各处理组中,轮叶黑藻干重的相对增长率随收割次数的增加呈现较明显的下降趋势,而根冠比随着收割次数的增多而增大。

The Vegetative Recovery of Hydrilla verticillata Under Several Harvesting Strategies

The effects of cutting intensity and frequency on the vegetative recovery of Hydrilla verticillata, grown in buckets with a water depth of 24 cm, were investigated in a series of 4 consecutive experiments with different cutting intensities at 6 cm, 12 cm and 18 cm from the apex of the plants, respectively through mid-May to late October, 2005. The results showed that both high cutting intensity and high cutting frequency prolonged the time of vegetative recovery of H. verticillata when the temperature variation was negligible. A period of 2 months was needed for the recovery of plants being cut off at 18 cm from the apex after the second and the third cut-offs, and 43 days for plants cut at 12 cm from the apex after the third cut-off, and less than a month for the rest cnt-offs. In late August, the number and length of both the normal shoots and the stolons declined significantly after the third cut-off at 18 cm from the apex of the plants, so the asexual propagation in the form of stolons or winter buds would be inhibited. All the other cutting time were within the booming season for H. verticillata, the number and the total length of normal shoots and stolons increased significantly after each cut-off, therefore the asexual propagation would not be inhibited. More than 75% of the new shoots were generated from the basal part of the plants after every cut-off, and those shoots constituted the fastest growing parts of the plants. Along with the increase in the times of cut-offs in all experimental groups, the relative increase rate of dry weight in H. verticillata declined significantly, but the root-shoot ratio increased.