Seasonal and spatial dynamics of allelochemicals in the submersed macrophyte Myriophyllum spicatum L

نویسنده

  • Elisabeth M. Gross
چکیده

Myriophyllum spicatum L. (or milfoil for short) is a highly competitive submersed macrophyte which can replace other submersed macrophytes and form monospecific stands. Frequently, epiphyte cover and phytoplankton development is low in M. spicatum dominated systems. Milfoil shoots grow fast and tall and tend to form canopies at the water surface depriving underlying photosynthetic organisms of light. M. spicatum exhibited the highest maximum photosynthetic rate (Vmax) in comparison with six other submersed macrophytes (MADSEN et al. 1991). M. spicatum spreads fast by vegetative fragmentation and can tolerate sediment resuspension better than many other submersed macrophytes (JOHNSON et al. 1998). Milfoil contains and releases algicidal phenolic compounds (PLANAS et al. 1981, GROSS et al. 1996), among them the major allelochemical tellimagrandin II (GROSS et al. 1996). Both released and tissue bound polyphenolic compounds from M. spicatum inhibit algal and cyanobacterial alkaline phosphatase activity (GROSS et al. 1996). Submersed macrophytes usually start growing in late spring, biomass maxima are reached in July or August while phytoplankton biomass maxima are reached in April/May and late summer (GOULDER 1969). An early production of allelochemicals by submersed macrophytes in spring could prevent light limitation by epiphytes, filamentous algae and phytoplankton. In many plants, low nitrogen supply can yield high concentrations of phenolic compounds and vice versa (e.g. ARNOLD et al. 1995). Milfoil growth is often N-limited (GERLOFF & KROMBHOLZ 1966). Previous investigations with axenic cultures of M. spicatum revealed the influence of light and nitrogen availability on the production of algicidal polyphenols (GROSS unpublished results). The aim of this study was to evaluate spatio–temporal variations in the production of algicidal hydrolysable polyphenols in M. spicatum. The amount of total phenolic compounds (TPC), concentrations of tellimagrandin II and the C/N ratio were determined in M. spicatum apical shoot segments from monospecific stands in four shallow ponds. The following hypotheses were tested. (1) Do concentrations of allelochemicals exhibit spatio–temporal variations? (2) Does the concentration of polyphenolic inhibitors depend on the nitrogen availability for M. spicatum?

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تاریخ انتشار 2001