Allelopathic activity of Stratiotes aloides on phytoplankton—towards identification of allelopathic substances

Abstract

The allelopathic activity of the aquatic macrophyte, Stratiotes aloides, was determined with laboratory experiments. Active compounds exuded in the medium or present in plant tissue were extracted using standard procedures and solid phase extraction (SPE). The activity towards various cyanobacteria and chlorophytes was tested in two different bioassay systems using agar plates and liquid cultures of phytoplankton. Extracts and exudates of S. aloides affected phytoplankton growth. SPE-enriched exudates and enriched water from a natural Stratiotes stand caused inhibition of target species, however, also some controls were active. Phytoplankton species exhibited differential sensitivity to extracts of S. aloides. We observed inhibitory and stimulatory effects on phytoplankton. In general, more cyanobacteria than other phytoplankton species were inhibited, and the inhibition of cyanobacteria was stronger. In most cases, nutrient (P or K) limitation of Synechococcus elongatus and Scenedesmus obliquus decreased the sensitivity of these species towards allelochemicals from Stratiotes aloides, except for P-limited cultures of Scenedesmus. The allelopathically active compound(s) from Stratiotes are moderately lipophilic and most likely no phenolic compounds. Our results indicate that allelopathy (besides nutrient interference and shading) might also account for the low phytoplankton and filamentous algae densities in the vicinity of Stratiotes plants, at least during certain phases of the life-cycle of Stratiotes.

Study on the release routes of allelochemicals from Pistia stratiotes Linn., and its anti-cyanobacteria mechanisms on Microcystis aeruginosa

“…The second most effective routes were residue decomposition and leaf leachates, while leaf volatilization showed no algae growth-inhibitory effect. The similar result also had been found in the aquatic plant of water hyacinth; the root of water hyacinth could release many anticyanobacteria allelochemicals (Malik 2007;Mulderij et al 2007). The difference might be caused by the different growth environment and physiological structures of terrestrial and aquatic plants.…”

Effects of artemisinin sustained-release granules on mixed alga growth and microcystins production and release

“…After 9 days, algal density began to increase, and M. aeruginosa had a greater increase rate. Similar results were obtained for other allelochemicals, while in general, cyanobacteria are considered more susceptible than green algae (Mulderij et al 2007;Zhu et al 2010). Although considerable differences have been observed among different cyanobacteria (Nakai et al 2000), as well as among green algal species (Hilt 2006), the results showed that the 16 mg L −1 group had a higher inhibition rate (about 60-70 %) during incubation process, and this concentration can be regarded as a good inhibition concentration.…”

Interaction between the macrophyte Stratiotes aloides and filamentous algae: does it indicate allelopathy?

“…The use of extracts (Jasser 1995) is no proof for allelopathic interactions between S. aloides and phytoplankton in situ (Willis 1985), and it provides no direct evidence that the plant actually releases allelopathic substances. Therefore, Mulderij et al (2005aMulderij et al ( , b, 2007 used S. aloides exudates (instead of extracts) to test the plant's allelopathic activity on several phytoplankton species. Mulderij et al (2005a) observed limitation of growth and colony formation of the green alga Scenedesmus obliquus (Turpin) Kützing when exposed to S. aloides exudates.…”