REGENERATION OF FRAGMENTS OF ELODEA NUTTALLII AND HYDRILLA VERTICILLATA

In order to identify the ability of asexual reproduction of the alien species Elodea nuttallii, and evaluate its ecological safety, the formation and growth of adventitious roots and buds of two submerged macrophytes, E. nuttallii and native species Hydrilla verticillata, were compared in an experiment. Intact shoots of the two species were cut into different fragment types, including 1-4 nodes. Observed in the laboratory for 4 weeks, we found that the fragments with apical buds showed the ability to form adventitious roots and young plants for both species. While the fragments without apical buds were not able to survive unless the axiliary bud was originally present. The percentage of adventitious roots’ formatted, and the lengths of roots and buds of the fragments were significantly higher for shoots with apical buds than those without apical buds of same nodes. The formation rate of adventitious roots for 4 node apical fragments in both species exceeded 90%. For the fragments without apical buds in the two species, the percentage and the length of buds and adventitious roots increased significantly with the increase of node number of the fragments. The bud percentage of all fragments were significantly greater than their rooting rate. In general, the shoots of E. nuttallii and H. verticillata had an axillary bud in every 7 nodes and 5 nodes respectively. The formation rate of new bud of both plants was from their axillary bud. Therefore, seven and five nodes were the shortest fragment size for E. nuttallii and H. verticillata without apical bud respectively to survive and regenerate. The vertical position of the node showed an appreciable effect on the growth of the root and bud in both species. The lengths of the roots and buds increased with the node-position’s closing the bottom of the fragment. However, the position effect was lower than the size effect in both species. The lengths of all-sized apical shoots and the biomass of 4 nodes apical shoots of E. nuttallii were significantly higher than those of H. verticillata. Other indices of E. nuttallii were significantly much lower than that of H. verticillata. In concluding, the reproductive capacity of E. nuttallii was lower than that of H. verticillata.