Physiology and dormancy of the aquatic angiosperm potamogeton crispus L. turions

Abstract

Vegetative buds (turions) are the major source of propagation for the aquatic invasive angiosperm, <italic>Potamogeton crispus</italic> L. (Potamogetonaceae). An understanding of the regulation of turion dormancy could lead to better methods of population control. The majority of <italic>Potamogeton crispus</italic> turions remain dormant over the summer and sprout in the autumn, while a small subset of turions remain dormant for an unspecified time. Hormonal control of dormancy in aquatic plant vegetative propagules is not well understood. For this study turions were divided into two different age groups, newly formed (current season) and older than one year (overwintered). The effect of varying light durations and temperatures on sprouting was monitored in these different groups. Non-structural carbohydrates, photosynthesis, and aerobic respiration were measured to determine metabolic activity. We also measured abscisic acid concentrations and sprouting levels in turions that were exposed to various hormones, temperatures, and light durations to elucidate hormonal control of dormancy. Current season turions were found to sprout mainly in response to day length and were metabolically active over a 6 week period. They are in a semi-dormant state and 60-70% will sprout in the autumn. The remaining current season turions presumably go into a state of deep dormancy and remain dormant over the winter. Turions that have overwintered are not photosynthetically active, have stable carbohydrate levels, and can remain dormant but viable for several years. Under laboratory conditions, they sprouted mainly in response to an increase in water temperature. These different age groups correspond to different turion physiological states and can explain sprouting variability recorded by other researchers. Current season turions produce and sprout in response to changes in ABA levels. A reduction of ABA in new turions is correlated with the breaking of dormancy. Overwintered turions do not sprout in response to ABA or GA changes. The results indicate two different pathways utilized by <italic>P. crispus </italic>turions to maintain and break dormancy.