PHENOTYPIC AND PHENOLOGICAL PLASTICITY OF AN AQUATIC MACROPHYTE MENYANTHES-TRIFOLIATA L

Phenotypic and phenological properties of Menyanthes trifoliata L. wer e investigated within and outside of a Phragmites australis (Cav.) Tri n. ex. Steud. canopy in a floating peat mat in Mizorogaike Pond, Centr al Japan. Under the P. australis canopy, M. trifoliata adjusted its ph enotypic properties to the conditions of decreased light by increasing leaf blade area, decreasing leaf blade thickness and elongating petio les. The earlier expansion of leaves of M. trifoliata within the P. au stralis community than outside the community was advantageous in terms of allowing the plant in the mixed community to produce as much dry m atter as possible before the foliage of P. australis could overgrow it . Despite the harmful effect of P. australis on M. trifoliata's vegeta tive growth and reproduction, the latter species can persist in a P. a ustralis community by changing its phenotypic and phenological propert ies.