The Vegetative Reproductive Characteristics of Stem Fragments in Potamogeton maackianus A.Benn.

The submerged macrophyte Potamogeton maackianus A.Benn.,with above-ground stolons,predominantly propagates by vegetative means in nature.Interconnected ramets frequently become separated or fragmentized by grazing fish or human activities.The segments can regenerate in new habitats to regrow into new individuals.The breakage of stem connections of P.maackianus was simulated to test if the survival and growth of the segments were affected by the fragment types(stolon type vs.shoot type) and their anchoring directions;and if a possible minimal length was needed to guarantee the regeneration of new individuals.The results showed that the survival rates and biomass of the individuals developed from stolon and shoot fragments of P.maackianus were significantly different and were obviously affected by the length of the fragments;but the number of the shoots germinating from the two types of fragments was similar.The shoot fragments can produce more younger ramets than stolon ones with the same internode number.The longer the fragments the larger the survival ramet rates.All most all the fragments of P.maackianus used in our experiment with 4 nodes can survive to new shoots.The directions of fragment anchoring significantly affected the ramet survival rates,the length of ramets,the node number bearing shoots and the root biomass;but little effects were found for the total ramet biomass.Their(survival) rates and anchoring ability of the fragments were favored by the normal direction of anchoring.