Abstract: Four consecutive cutting experiments were conducted to investigate the effects of cutting intensity, cutting frequency, and cutting date on the re-growth of Myriophyllum spicatum. The M. spicatum plants were cultured in buckets with a water depth of 24 cm, and three cutting intensities were taken at 6, 12 and 18 cm from the apex of the plants, respectively. The results showed that after the first cut-off at 18 cm from the apex in late August, the plants recovered after 41 days, but fewer lateral shoots generated. Therefore, the asexual reproduction would be negatively affected in this case. In contrast, the plants subjected to two initial cut-offs at 6 or 12 cm from the apex before late September recovered after 55 days, with more lateral shoots generated and with significant increase in total shoot length, which meant that the asexual reproduction would not be inhibited. After a second cut-off at 18 cm in early October or a third cut-off at 6 or 12 cm before late November, all the plants could survive in winter, with a recovery span of at least 4 months. The new shoots after each cutting were generated mostly from the cut place (over 40%), and secondly from turions (0〖KG-*2〗-〖KG-*7〗413%). The relative increase rate of dry mass declined, while the root/shoot ratio increased with the number of the cuttings.

Key words: Oryza sativa, Free-air CO₂ enrichment (FACE), Phosphorus uptake, Phosphorus distribution, Phosphorus efficiency