STUDIES ON REPRODUCTION DIVERSITY IN POTAMOGETON PECTINATUS
蓖齿眼子菜繁殖多样性研究

Potamogeton pectinatus is a perennial submerged aquatic macrophyte with a parvopotamid growth form. It inhabits many different environments from the south to the north in China. According to observation in Dianchi Lake, P. pectinatus is a tolerant species with wide ecological amplitude and can survive in heavy polluted waters. Presently, Dianchi Lake has been seriously polluted. Cyanobacteria blooms were serious, which led to a low transparency. While the other submerged aquatic macrophytes have disappeared, this species still occurs in Dianchi Lake. This suggests that P. pectinatus must possess various survival strategies being worthy of further research. Reproduction is a key factor influencing survival, distribution and dynamic variation of community structure. In this paper, reproduction diversity of P. pectinatus was studied through experiment and observation in situ. The results showed that pollination of P. pectinatus is by way of bubble enveloping for flowers that are underwater and pollen floating when flowers are at the water surface in sexual reproduction. The fruit-set efficiency in P. pectinatus that are underwater was low, being only 6.41% , compared to 24. 38% of flowers reaching the surface. Seed number of P. pectinatus in exposed, and sheltered or pond sites is 794, 1 627 and 2 140 per square meter, respectively. Seed germination rate of P. pectinatus was under 6% in Dianchi Lake. As a result, sexual reproduction is not important to regenerate populations of P. pectinatus . This species also possesses an extensive and effective system of asexual reproduction, through shoot fragments , rhizomes, stem tubers, root tubers and axillary shoot regeneration. The populations of this species are mainly produced from the root tubers and rhizomes. Asexual reproduction has a large contribution to population restoration during the next growth season. The main function of the seeds appears to be dispersal and long-term survival of the species. In addition, some suggestions for aquatic vegetation restoration by this species were put forward according to the results of experiment and observation.