Growth and development of the facultative root hemiparasite Rhinanthus minor after removal of its host

2007 ◽  
Vol 34 (3) ◽  
pp. 237 ◽  
Author(s):  
Fan Jiang ◽  
Leila Timergalina ◽  
Guzel Kudoyarova ◽  
W. Dieter Jeschke ◽  
Wolfram Hartung
Keyword(s):  
Root System ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Soil Microorganisms ◽  
Xylem Sap ◽  
Optimal Growth ◽  
Root Hemiparasite ◽  
Host Root ◽  
Stomatal Behaviour ◽  
Growth Promoting

Facultative plant hemiparasites exhibit optimal growth only when attached to a suitable host. After attachment, stomata of the parasite remain continuously open, thus, optimising the extraction of host xylem sap. When the host shoot was removed from the hemiparasitic Rhinanthus/barley association ~14 days after attachment, the resulting host-free attached Rhinanthus continued to grow and develop similarly well as the attached parasites. These plants, however, showed altered stomatal behaviour: their stomata were open at daytime and closed at night, whereas parasitising Rhinanthus has continuously open stomata all day and night and unattached single Rhinanthus has practically closed stomata throughout day and night. After removal of the host the root growth was strongly increased, thereby increasing the root-to-shoot ratio. Abscisic acid and cytokinin relationships became more ‘normal’ with the Rhinanthus roots becoming able to synthesise zeatin nucleotides and zeatin ribosides, thus, behaving much as non-parasitic plants in general. It is suggested that the degrading root system of the host plant produces signals that trigger this conversion. Two explanations for these changes are discussed, the supply of dissolved organic nitrogen by the degrading host root system and a possible strong growth of growth promoting soil microorganisms using the degrading host root system as a substrate.

Responses to dissolved organic nitrogen compounds by recently isolated freshwater microalgae species

2020 ◽  
Author(s):  
Catherine E. Bayliss ◽  
Penny Johnes ◽  
Richard P. Evershed ◽  
Patricia Sanchez-Baracaldo ◽  
Stephen C. Maberly
Keyword(s):  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Nitrogen Sources ◽  
Optimal Growth ◽  
Nitrogen Addition ◽  
Ecosystem Functions ◽  
Anthropogenic Activity ◽  
Nitrogen Compounds ◽  
Freshwater Microalgae ◽  
Nitrogen Inputs

<p>Freshwater microalgae isolates from a UK headwater catchment (collected in 2017) were tested for their growth and media nitrogen speciation changes when presented with low molecular weight dissolved organic nitrogen compounds. The location has input from livestock run off increasing organic matter in stream. Experimental treatments and initial isolation took place in controlled culture cabinets kept at 15°C, with a 16:8 light:dark cycle and light c.a. 50 µmol m<sup>-2</sup> s<sup>-1</sup>. Treatments included separately presented urea and glutamate, alongside negative (no N or P sources) and positive controls (nitrate or ammonium). Nitrogen addition treatments were provided with the same phosphorus source, trace minerals, trace metals and took place for two weeks. Different species isolated from the location showed optimal growth on different organic nitrogen sources. Organic nitrogen compounds caused growth at least comparable to inorganic sources. Cell growth was best on dissolved organic nitrogen compounds for some species. This relatively quick cycling of organic nitrogen compounds in river systems to photosynthetic growth has implications for ecosystem heath and capacity to mitigate organic nitrogen inputs. Anthropogenic activity that increases organic nitrogen may favour certain species compositions, altering downstream ecosystem functions such as algal bloom formation and dominant microalgae species. Further work will use stable isotope investigation of potential uptake mechanisms and wider work is required on understanding how the ecosystem may respond to organic nitrogen changes. </p>

Electro-Oxidation to Convert Dissolved Organic Nitrogen and Soluble Non-Reactive Phosphorus to More Readily Removable and Recoverable Forms

Chemosphere ◽  
2021 ◽  
pp. 130876
Author(s):  
Synthia P. Mallick ◽  
Donald R. Ryan ◽  
Kaushik Venkiteshwaran ◽  
Patrick J. McNamara ◽  
Brooke K. Mayer
Keyword(s):  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Electro Oxidation ◽  
Reactive Phosphorus

scholarly journals Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

2013 ◽  
Vol 10 (11) ◽  
pp. 7609-7622 ◽  
Author(s):  
M. Alkhatib ◽  
P. A. del Giorgio ◽  
Y. Gelinas ◽  
M. F. Lehmann
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Bottom Water ◽  
Estuarine Sediments ◽  
Internal Source ◽  
Lawrence Estuary ◽  
Element Partitioning ◽  
Sediment Porewaters ◽  
St Lawrence Estuary

Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment porewaters was determined at nine locations along the St. Lawrence estuary and in the gulf of St. Lawrence. In a previous manuscript (Alkhatib et al., 2012a), we have shown that this study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, and benthic respiration rates. Based on the porewater profiles, we estimated the benthic diffusive fluxes of DON and DOC in the same area. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1). DON fluxes were positively correlated with sedimentary POM reactivity and varied inversely with sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30 to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange, a result that is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. In contrast to DON, DOC fluxes out of the sediments did not show any significant spatial variation along the Laurentian Channel (LC) between the estuary and the gulf (2100 ± 100 μmol m−2 d−1). The molar C / N ratio of dissolved organic matter (DOM) in porewater and the overlying bottom water varied significantly along the transect, with lowest C / N in the lower estuary (5–6) and highest C / N (> 10) in the gulf. Large differences between the C / N ratios of porewater DOM and POM are mainly attributed to a combination of selective POM hydrolysis and elemental fractionation during subsequent DOM mineralization, but selective adsorption of DOM to mineral phases could not be excluded as a potential C / N fractionating process. The extent of this C- versus N- element partitioning seems to be linked to POM reactivity and redox conditions in the sediment porewaters. Our results thus highlight the variable effects selective organic matter (OM) preservation can have on bulk sedimentary C / N ratios, decoupling the primary source C / N signatures from those in sedimentary paleoenvironmental archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

Synergistic Adsorbent Sequence for Dissolved Organic Nitrogen Fractional Removal from Biotreated Pharmaceutical Wastewater

2021 ◽  
Vol 1 (4) ◽  
pp. 991-1001
Author(s):  
Haidong Hu ◽  
Yuanji Shi ◽  
Kewei Liao ◽  
Xinyu Xing ◽  
Caifeng Liu ◽  
...  
Keyword(s):  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Pharmaceutical Wastewater
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