Field and greenhouse investigations on winter bud production by Potamogeton gramineus L.

Abstract

Potamogeton gramineus L. winter buds were present in the Byrnes Canal in northern California from August through October. Density (number m −2) of winter buds increased during this period and was inversely related to photoperiod. Density varied from year to year (1985–1991) and maximum average density of 761 m −2 was recorded in 1986. In greenhouse experiments, winter buds were present on plants after 8–10 weeks of growth at a 10 h photoperiod, but not at a 14 photoperiod. Plants grown at a 10 h photoperiod but with the dark period interrupted with either 20 or 60 min of dim light at 13 μM m −2 s −1 did not produce winter buds. Similar plants grown at a 10 h photoperiod with no interruption of the dark period produced winter buds. Plants grown with interruption of the dark period displayed dry matter allocation patterns similar to plants grown at a 16 h photoperiod. This information confirms earlier reports with other species about the importance of photoperiod for initiating vegetative propagule formation, and will improve capabilities for predicting vegetative reproduction by rooted aquatic plants.