TURIONS OF MYRIOPHYLLUM-EXALBESCENS

Turions of M. exalbescens Fernald in Snelling Lake, Minnesota, were investigated and found to be a most important feature of the life history of this species for 6 months of the year. Initiation of turion formation on lateral and terminal stem apices occurred in September or October and the turions then elongated gradually, becoming heavier during October and November. During the winter, turions became less buoyant and by April had sunk to the bottom and assumed the U-shape characteristic of the base of plants grown from turions. Turions were shown to remain attached to the previous season's growth until released by decay of the parent plant. No abscission layer at the base of turions was found. It was the onset of turion formation and the prolonged period of turion dormancy that limited the growing season of M. exalbescens. A winter vernalization period for turions appeared to be essential for normal plant development the following season. © 1979.