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, ).…”

Transcriptome and functional analyses of phenotypic plasticity in sea grape Caulerpa okamurae

“…Our initial experiment confirmed that irradiance could influence C. okamurae 's phenotype. Macrophytes also alter their cellular structure, cytoskeletal organization, and overall morphology to reduce hydrodynamic forces from continuous mechanical stress (Atapaththu et al, 2015; Bal et al, 2011; Bornette & Puijalon, 2011; Puijalon et al, 2008; Sampathkumar et al, 2014; Sand‐Jensen, 2003; Starko et al, 2015). With this in mind, the absence of wave‐induced stress in the initial experiment led to a significant downregulation of genes associated with mechanical stress (Figure 4c and Supporting File 2).…”

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).…”