Influence of cutting leaves of lotus plants Nelumbo nucifera on their survival.

Abstract

In eutrophied lakes, water pollution and degradation of biodiversity are caused by the overgrowth of lotus (Nelumbo nucifera). For this reason, lotus management activities, such as mowing, have been conducted in several lakes. To develop an effective method to control lotus plants, the influence of mowing on their survival was evaluated in a test pond adjacent to Lake Izunuma-Uchinuma in Japan. Leaves of twenty-two ramets of lotuses, each with 2-36 leaves, were cut at 40 cm under the water surface. Of these leaf-bearingramets of lotuses, eight (36.4%) were dead. The mean number of leaves of the dead lotus ramets before cutting (4.5±0.8 leaves) was less than half the number of leaves of the surviving lotus ramets (11.9±2.8 leaves). However, cutting the leaves of 11 ramets oflotuses prevented the growth of new leaves on the water surface within three days, after which all lotuses died regardless of the number of leaves the ramets had before cutting. These results suggest that the emergence of leaves is an important factor determininglotus survival. Therefore, it is suggested that repeatedly cutting lotus ramets when they have fewer leaves is an effective method to control lotus plants.