Seasonal Changes in Carbohydrate and Nitrogen Concentrations in Oregon and California Populations of Brazilian Egeria (Egeria densa)

Abstract

Total nonstructural carbohydrate (TNC) reserves support growth, formation of reproductive structures, and sprouting of plant tissues, and nitrogen (N) is essential for amino acid synthesis and photosynthetic enzyme production. Timing of weed management to periods when these critical resources are most limiting might improve efficacy. We examined seasonal changes in carbohydrate and nitrogen concentrations in Brazilian egeria (Egeria densa), a common submersed aquatic weed, from two locations in the United States. Plants were collected from a coastal Oregon reservoir and from California's Central Valley in the Sacramento–San Joaquin Delta. Starch comprised between 35 to 51% of the TNC in lower stems and root crowns. Seasonal changes in resource concentrations were not consistent between years within a population or for the same plant part between different populations. Lowest TNC concentrations were observed earlier in the growing season (March) in Disappointment Slough than in Big Creek (May to June). Conversely, highest concentrations were observed in October in Disappointment Sough and from August to March in Big Creek. Nitrogen concentrations were highest in stem tips in both populations, with more distinct seasonal changes in the California population. These data suggest western populations of E. densa might exhibit less-discernible low points in root crown and lower stem energy storage for targeting management activities to vulnerable phenological stages. Brazilian egeria has high phenological plasticity despite its low genetic diversity and lack of specialized reproductive and perennating structures, which allows the plant to invade and dominate submersed plant communities in areas with mild winters.

Effects of invasive species on plant communities: an example using submersed aquatic plants at the regional scale

“…Bold values represent the total area where the species was found in the fall and again in the summer Effects of invasive species on plant communities 451 constant flow (Pennington and Sytsma 2009). Thus, as native submersed plant species senesce in the fall, E. densa continues producing biomass, some of which persists through the winter.…”

“…Franks Tract), and these actions are likely to reduce areal cover of this species (Santos et al 2009) and could eventually change the composition back to a native species dominated community. Management of E. densa is complicated by its bimodal growth periods, late spring and autumn, (Pennington and Sytsma 2009), and by the large spatial extent of the Delta. This unique growth pattern would require multiple management actions throughout the year to overcome its competitive growth advantage, which would increase management costs substantially.…”

Variation in tussock architecture of the invasive cordgrass Spartina densiflora along the Pacific Coast of North America

“…Total nonstructural carbohydrates (TNC) concentrations in rhizomes decreased with lower salinities (lower electrical conductivities), which could reflect the depletion of rhizome reserves due to growth stimulation under brackish conditions, where S. densiflora has been described as a highly competitive species (Costa et al 2003). Depletion of carbohydrate reserves during rapid growth has been reported in several other submersed and emergent aquatic plants such as Phragmites australis (Granéli et al 1992;Č ižková et al 2001), Egeria densa (Pennington and Sytsma 2009), and Myriophyllum spicatum (Perkins and Sytsma 1987;Madsen 1997). Rhizome dynamics are very important in salt marsh development in a changing world since rhizome accumulation is key to maintaining soil volume with b Fig.…”

Seasonal variations of carbohydrates in Pueraria lobata related to growth and phenology

“…By understanding the phenology of the target plant and the fate of carbohydrates, there is the possibility to identify any potential "weak points" in the life cycle. Previous research on other plant species has demonstrated successfully that timing the control technique to the target plant's low point in carbohydrate storage can increase the effectiveness of management (Richburg 2005;Pennington & Sytsma 2009).…”