Osmotically Active Compounds and their Localization in the Marine Halophyte Eelgrass

Short-term impacts of salinity pulses on ionic ratios of the seagrasses Thalassia testudinum and Halodule wrightii

“…Overall ion concentration in the leaves and rhizomes of both seagrass species decreased from Clto Na + to K + to Ca +2 . This differs from past results reported for Zostera marina, where concentrations decreased from Na + to K + to Clto Ca +2 in both leaves and rhizomes (Ye and Zhao, 2003). Perhaps ion accumulation processes in Z. marina are more similar to marine macroalgae, which also accumulate high Na + and K + concentrations (Touchette, 2007).…”

“…Perhaps ion accumulation processes in Z. marina are more similar to marine macroalgae, which also accumulate high Na + and K + concentrations (Touchette, 2007). In addition, Na + , Cland K + concentrations were higher in leaves than rhizomes in Z. marina (Ye and Zhao, 2003), whereas Cl -, Na + , K + and Ca +2 concentrations were higher (more than twice) in rhizomes than leaves in T.…”

“…Seagrasses can accumulate salt in concentrations equaling or exceeding those in seawater without any harmful impacts on the plant (Flowers et al, 1977). Specifically, seagrasses accumulate sodium (Na + ), potassium (K + ) and chloride (Cl -) (Touchette, 2007) and these concentrations may vary among seagrass species and organs of the same plant (Birch, 1975;Ye and Zhao, 2003).…”

“…Aquatic plants can take up ions via roots, shoots and leaves (Babourina and Rengel, 2010), and maintenance of adequate levels of K + and Ca +2 is essential for plant survival. Seagrass cells store Cland Na + in vacuoles to avoid elevated cytoplasmic concentration and resulting physiological damage (Carpaneto et al, 1997;Ye and Zhao, 2003;Touchette, 2007). When Cland Na + are sequestered in the cell vacuole, K + and other organic osmolytes accumulate in the cytoplasm and balance the cell osmotic pressure (Davison and Reed, 1985;Kirst, 1989;Touchette, 2007).…”

“…There are several A c c e p t e d M a n u s c r i p t 3 studies of the influence of salinity on these seagrasses, ranging from impacts on growth and survivorship (McMillan and Moseley, 1967;McMahom, 1968;McMillan, 1974;Lirman and Cropper, 2003;Koch et al, 2007) to physiological parameters, carbohydrates, and osmolality (Berns, 2003;Koch et al, 2007), and seedling performance (Kahn and Durako, 2006). However, few studies have investigated the response of ion concentrations and the function of inorganic solutes in osmotic adjustment in seagrasses (Tyerman, 1982;Tyerman et al, 1984;Ye and Zhao, 2003;Touchette, 2007;Marín-Guirao et al, 2013), and to our knowledge, there are no studies to date. The purpose of the present study was to examine the short-term impacts of salinity pulses on inorganic ion concentrations in leaves and rhizomes of the seagrasses T. testudinum and H. wrightii.…”