Effects of water turbulence on variations in cell ultrastructure and metabolism of amino acids in the submersed macrophyte, Elodea nuttallii (Planch.) H. St. John

Abstract

The interactions between macrophytes and water movement are not yet fully understood, and the causes responsible for the metabolic and ultrastructural variations in plant cells as a consequence of turbulence are largely unknown. In the present study, growth, metabolism and ultrastructural changes were evaluated in the aquatic macrophyte Elodea nuttallii, after exposure to turbulence for 30 days. The turbulence was generated with a vertically oscillating horizontal grid. The turbulence reduced plant growth, plasmolysed leaf cells and strengthened cell walls, and plants exposed to turbulence accumulated starch granules in stem chloroplasts. The size of the starch granules increased with the magnitude of the turbulence. Using capillary electrophoresis-mass spectrometry (CE-MS), analysis of the metabolome found metabolite accumulation in response to the turbulence. Asparagine was the dominant amino acid that was concentrated in stressed plants, and organic acids such as citrate, ascorbate, oxalate and γ-amino butyric acid (GABA) also accumulated in response to turbulence. These results indicate that turbulence caused severe stress that affected plant growth, cell ultrastructure and some metabolic functions of E. nuttallii. Our findings offer insights to explain the effects of water movement on the functions of aquatic plants.

Effects of mechanical stressors caused by mean flow and turbulence on aquatic plants with different morphologies

“…Starch also accumulates as a defensive mechanism in plants exposed to the stresses of ammonium nitrogen and high salinity (Ariovich & Cresswell, ; Wang et al, ). Therefore, the excessive starch that accumulated in cortex cells might be a response to the increase in stress generated by high turbulence velocities; however, the link between starch accumulation and the stress response remains to be fully elucidated (Atapaththu et al, ).…”

“…However, the mechanical effects of these two flow components may differ on aquatic plants. Whereas mean flow exerts tension stress on the plant body parallel to the direction of flow (Bornette & Puijalon, ), turbulence loads mechanical forces and pressures in varying directions on the plant body (Atapaththu & Asaeda, ; Atapaththu et al, ; Ellawala, Asaeda, & Kawamura, ).…”

Plants in aquatic ecosystems: current trends and future directions

“…Macrophytes can be affected at scales, from individual plants to populations and communities. This is exemplified by plant growth which is known to be influenced from the microscale, for example, cell ultrastructure (Atapaththu et al, 2015), to macroscale, for example, biomechanical traits (Puijalon et al, 2011;Schoelynck et al, 2014). Current developments in our understanding of these complex twoway interactions between aquatic vegetation and physical factors are tightly linked to fluid dynamics modelling (Marjoribanks et al, 2014;Verschoren et al, 2016).…”

The Growth of Vallisneria natans and Its Epiphytic Biofilm in Simulated Nutrient-Rich Flowing Water

“…Water flow promotes the activity of nitrifying microorganisms by increasing the concentration of DO, which is conducive to nitrification, thereby promoting the transformation of ammonia nitrogen [17]. An appropriate water flow can promote the exchange of oxygen and the supply of nutrients [18,19], thereby helping oxygen and nutrients reach the submerged microphytes in biofilm leaves where microorganisms affect the growth of epiphytic biofilm and the succession of the microbial community in submerged macrophytes [16,20,21]. However, it is a challenge for submerged macrophytes to exist in some heavily eutrophic aquatic ecosystems due to competition from anaerobic bacteria and cyanobacteria and other eutrophic algae, which is not conducive to the growth of submerged macrophytes [22].…”