Phenology, starch allocation, and environmental effects on Myriophyllum aquaticum

Seasonal biomass and starch allocation patterns were determined from natural populations of Myriophyllum aquaticum that were sampled monthly from January 2006 to December 2007 in Mississippi. Water temperature, water depth, light irradiance, light transmittance, pH, and conductivity were also recorded during biomass harvests. Overall, few significant relationships were observed between the environmental factors tested and seasonal biomass. Submersed shoot biomass was negatively related (p < 0.01) with water temperature. Stolons accounted for 40–95% of total biomass followed by emergent shoot, submersed shoot, and root biomass. Percent starch in plant tissues was positively related to water temperature. Starch allocation was greatest in stolons where up to 16.3% of total starch was stored. Submersed shoots stored 0.6–11.0% of total starch followed by emergent shoots (0.4–7%). The roots of M. aquaticum stored less than 3.8% of total starch throughout the study period. Reduced biomass and starch storage occurred from October to March in both 2006 and 2007. Management strategies for this species could utilize an integrated approach to exploit times of low energy reserves (fall and winter), or to remove emergent shoots to gain access to the stolons and other submersed tissues.

► The majority of carbohydrates in M. aquaticum are stored in the stolons.
► Stolons comprised the greatest proportion of biomass throughout the year.
► Water temperature was the greatest environmental driver of growth and biomass allocation.