Nitrogen nutrition of Myriophyllum spicatum: uptake and translocation of ¹⁵N by shoots and roots

Abstract

Summary Intact Myriophyllum spicatum plants were grown in compartmentalized containers in a growth room so that the roots were separated from the shoots by a watertight partition. Nitrogen 15N was added to the water or sediment to trace the uptake of inorganic N by the plant shoots or roots. Myriophyllum spicatum is capable of taking up inorganic N through both roots and shoots. Plant N requirements can apparently be met by root uptake alone. However, when about 0·1 mg/l of NH4‐N were present in the water, foliar uptake supplied more N to the plants than did root uptake. Foliar uptake of NH4‐N was found to be several times faster than that of NO3‐N when both forms of N were present in the water. Only about 1% of the N taken up by the roots was subsequently released to the water through the foliage.

Importance of Nutrient Competition and Allelopathic Effects in Suppression of the Green Alga Scenedesmus obliquus by the Macrophytes Chara, Elodea and Myriophyllum

“…Since this reduction is much higher than the 12-28% found in nutrient-enriched culture filtrates, the difference may be caused by rapid nutrient removal in the presence of the plants (Nichols & Keeney, 1976;Van Donk et al, 1993;Kufel & Kufel, 2002). The remaining growth inhibitory effect in filtrates from Elodea is then most likely a result of allelochemicals.…”

“…Nutrients were added to filtrates from phase I plant-free controls and macrophyte treatments to prevent nutrient limitation for Scenedesmus in phase II, as Scenedesmus, and Chara, Myriophyllum and Elodea shoots in phase I could have depleted nutrients (Nichols & Keeney, 1976;Van Donk et al, 1993;Kufel & Kufel, 2002). Since Scenedesmus growth and morphology was unaffected in standard WC-medium or medium that contained 2.5 times more nutrients, masking of a potential allelochemically exerted growth inhibition by nutrient enhanced growth seems unlikely.…”

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

“…The higher SC contents in the root than in the leaf and stem of M. spicatum reflects the root acting as locations for energy-exhausting metabolisms, e.g., absorption and assimilation of nitrogen and phosphorus from sediment particularly in oligotrophic lakes (Nichols and Keeney 1976;Best and Mantai 1978). Nichols and Keeney (1976) found that M. spicatum absorbed NH 4 + mainly by the leaf rather than by the root when NH 4 N in water column was about 0.1 mg L −1 .…”

“…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).…”

Allelopathy of Aquatic Autotrophs

“…He considered either a "nitrogen sink" effect or antagonistic (allelopathic) interference to be responsible for the inhibition of epiphytes in cultures of Myriophyllum sp., Ceratophyllum sp., Lemna minor, Cladophora sp., and Pithophtora oedogonium. Myriophyllum, the only rooted species in this list, can take up nitrogen both with shoots and roots, depending on the concentrations in the respective compartments (Nichols and Keeney, 1976a). All others obtain nitrogen primarily from the water.…”