Carbon and nitrogen metabolism of an eutrophication tolerative macrophyte, Potamogeton crispus, under NH4+ stress and low light availability

Nitrogen/carbon metabolism in response to NH4+ pulse for two submersed macrophytes

“…Accumulation of NH 4 + and FAA in plant tissues was also reported for other submersed macrophytes under NH 4 + stress, such as Vallisneria natans L. , Potamogeton crispus L. (Cao et al, 2009b), Potamogeton maackianus A. Benn. (Li et al, 2007), Stratiotes aloides L. (Smolders et al, 1996).…”

“…In general, free NH 3 decreases chlorophyll contents (Rudolph and Voigt 1986) and inhibits respiration and affects electron transport system of plant (Vines and Wedding, 1960). To prevent NH 4 + toxicity, many macrophytes decrease NH 4 + accumulation by incorporating it into free amino acids (FAA) and amines and/or by actively transporting it out of plant cells, which are processes requiring carbon (C) as energy and C-skeleton for FAA synthesis (Britto et al, 2001;Britto and Kronzucker 2002;Cao et al, 2009a), leading to imbalance of CN metabolism under NH 4 + stress, e.g., increases in NH 4 N and FAA and decreases in soluble carbohydrate (SC) and starch (Cao et al, 2009b;Zhang et al, 2010;Yuan et al, 2013). The effect of NH 4 + enrichment on plants depends on the C reserves, e.g., sufficient C reserves alleviated negative effects of NH 4 + enrichment on Zostera noltii and Potamogeton crispus (Brun et al, 2002;Cao et al, 2009b In this study, the submersed macrophytes Myriophyllum spicatum L. and Ceratophyllum demersum L. were used to test effects of NH 4 + pulse on their C and N metabolism, because (1) these species distributed worldwide and inhabit waters ranging from mesotrophic-to eutrophic-conditions (Aiken et al, 1979;Smith and Barko 1990;Mjelde and Faafeng 1997); (2) they prefer NH 4 + over NO 3 − (Nichols and Keeney 1976;Best 1980), and require a considerable quantity of N for biomass production (Goulder and Boatman 1971;Wersal and Madsen 2011); and (3) they represent two kinds of strategies in resource use (Poorter and Bongers 2006;Sterck et al, 2011), with M. spicatum having an acquisitive strategy and higher growth rate (Fu et al, 2012) and C. demersum having a conservative strategy, with a more conservative C use and higher tress tolerance (Yuan et al, 2013;Zhong et al, 2013).…”

Does the responses of Vallisneria natans (Lour.) Hara to high nitrogen loading differ between the summer high-growth season and the low-growth season?

“…When experiencing high NH 4 stress, macrophytes may excessively synthesize FAA to avoid NH 4 toxicity. Such a process costs energy and consumes carbohydrates (Rare, 1990;Krupa, 2003), which may reduce the growth of macrophytes, particularly at low light availability (Cao et al, 2009a(Cao et al, , 2009bYuan et al, 2013Yuan et al, , 2016. The content of FAA is therefore commonly used as an indicator of nitrogen stress (Cao et al, 2009a;Yuan et al, 2015;Zhang et al, 2010).…”

“…Growth of phytoplankton is typically higher in summer, implying stronger shading. This may affect the NH 4 stress on submersed macrophytes because the physiological stress of NH 4 is light-dependent (Cao et al, 2009b. The negative effects of nitrogen will therefore expectedly be strongest during the warm season.…”

Fertile sediment and ammonium enrichment decrease the growth and biomechanical strength of submersed macrophyte Myriophyllum spicatum in an experiment

“…into free amino acids (FAA) at the expense of soluble carbohydrates (SC) consumption (von Wiren et al, 2000;Coruzzi & Zhou, 2001;Cao et al, 2009). Additionally, autofragments of Myriophyllum spicatum were reported to have higher survival and recruitment due to its higher TNC storage than the allofragments (Kimbel, 1982;Smith et al, 2002).…”