RHIZOME GROWTH OF MENYANTHES-TRIFOLIATA L IN A POPULATION ON A FLOATING PEAT MAT IN MIZOROGAIKE POND, CENTRAL JAPAN

The growth of rhizomes of Menyanthes trifoliata L. was investigated in a floating mat in central Japan in order to examine the phenotypic pr operties of the rhizomes and hence to clarify the role of these organs . The part of the rhizome which elongated in autumn had high specific dry weight during autumn and winter, and the specific dry weight decre ased in early spring when generative buds and leaves started to develo p. This part of the rhizome has a function for dry matter storage, The part of the rhizome which elongated in summer had a low specific dry weight. Rhizomes with low specific dry weight are thin and long and ar e useful for occupation of the peat surface, hence playing a role in v egetative expansion. The percentage of generative buds and lateral bud s formed was related to the size of rhizomes formed in the preceding y ear, The percentage of generative bud formation increased with increas ing rhizome size, In contrast to generative buds, lateral bud formatio n was restricted to rhizomes 2-32 cm in length: rhizomes longer than 3 2 cm never formed lateral buds.