Two stages of dormancy in turions of Potamogeton crispus L.

Vegetative buds (turions) are the major source of propagation for the aquatic invasive angiosperm, Potamogeton crispus L. A better understanding of the factors that regulate turion dormancy and sprouting would lead to better methods of population control. Turions were collected and divided into two age groups: new, current season turions; and overwintered turions that were at least 1 year old. Sprouting was monitored in these two groups exposed to varying light durations and temperatures. Glucose and starch content and photosynthesis were also determined. Current season turions are dormant but metabolically active over a 6 weeks period. A small percentage of these new turions sprouted in response to short day-long night light durations at a temperature of 23. °C. Turions that did not sprout progressed to a deeper stage of dormancy similar to overwintered turions. Overwintered turions were not photosynthetically active and had stable carbohydrate levels. Under laboratory conditions, a large percentage of these turions sprouted in response to warming to 23. °C and further stimulated by exposure to any light duration. These different stages of dormancy based on age can explain much of the variability in turion sprouting reported by other researchers. A small percentage of both types of turions maintain a prolonged state of dormancy that is not broken by external stimuli.