Influence of propagule size, soil fertility, and photoperiod on growth and propagule production by three species of submersed macrophytes

Abstract

Potamogeton pectinatus, P. gramineus, and monoecious ltydrilla verticillata were grown in greenhouse experiments at 2 photoperiods, 5 levels of sediment nutrients, and from initial propagules of 3 different size classes to determine how these factors influenced growth and production of vegetative propagules. Potamogeton pectinatus weight increased with increasing tuber size and soil fertility, but differences between plants grown at two photoperiods were small. Mean weight of tubers was greater for plants grown under a 10-h photoperiod and from tubers in the medium or large size class. Tuber production by plants grown from small tubers under a 10-h photoperiod was much less and was about the same as that for all plants grown under the 16-h photoperiod whatever the initial tuber size. Potamogeton gramineus weight was greater for plants grown on more fertile soils at the 16-h photoperiod. Plant weights at the 10-h photoperiod were less affected by soil fertility. Plants from larger winter buds weighed more. Winter buds were only produced under the 10-h photoperiod. For 1t. verticillata, there were several significant interactions. In general, plants from larger tubers weighed more if they grew on more fertile soils or at the 16-h photopefiod. Plants grown at the short photoperiod produced more tubers with increasing soil fertility and with increasing propagule size. These results imply that propagule size may be important in determining aquatic plant persistence in an area through its effects on growth and propagule production.

Plant Performance Across Latitude: The Role of Plasticity and Local Adaptation in an Aquatic Plant

“…In southern sites, characterized by high population densities and high biomass standing crop (due to the mild winters and better growth conditions during springsummer; L. Santamaría, personal observation), this trait will probably confer a competitive advantage to the local genets. Mediterranean genets showed greater plasticity in shoot-to-root ratio (a trait also involved in light-competition responses) than the midlatitude genets, and they produced larger tubers, which are known to confer a competitive advantage in dense populations (Spencer and Ksander 1995). It is however remarkable that the Swedish genets showed a similar pattern of variation.…”

Influences of water column nutrient loading on growth characteristics of the invasive aquatic macrophyte Myriophyllum aquaticum (Vell.) Verdc.

“…These new competitors that are capable of higher growth rates may have long-term negative impacts to native community composition (Kennedy et al, 2009). Nutrient amendment studies for aquatic plants have typically focused on enrichment of sediment nutrients, as the sediment is often considered the most important source of nutrients for aquatic plants (Barko & Smart, 1981, 1986Spencer & Ksander, 1995). However, as the amount of nutrients finding their way into waterbodies increases, understanding the effects of water column enrichment on macrophyte communities, invasive species, and the invasion process will become more important (Kennedy et al, 2009).…”

Endozoochorous dispersal of aquatic plants: does seed gut passage affect plant performance?

“…Although we lack quantitative information on the rates of herbivory and seed predation by ducks on Potamogeton pectinatus in southern Spain, it is important to note that seed ingestion can take place at any time between fruit production in July through August and late winter (e.g., seeds of Ruppia and other marsh plants were consumed by ducks all winter, and in some cases, their presence in duck feces was higher at the end of the winter than in autumn; Figuerola et al, , 2003. Perennation of plants through tubers, which have a higher competitive ability than seeds owing to their higher germinability and much larger reserve storage (Van Wijk, 1989;Spencer and Ksander, 1995) could also enhance the fitness advantage of early germinating seeds. However, seed banks represent an insurance against habitat instability (Thompson, 2000).…”