Assessing Performance Differences Of Aquatic Macrophytes-Ceratophyllum Demersum,Vallisneria Natans,and Potamogeton Maackianus Under Different Ammonium Concentration Treatments

Nitrogen metabolism is central to the growth and development of plants since it provides building blocks for the synthesis of biomolecules such as proteins,nucleic acids and chlorophyll.Ammonium is a significant inorganic form of nitrogen(critical limiting element)necessary for the establishment of aquatic plants.It is a preferred source of nitrogen for most aquatic macrophytes since its assimilation consumes less energy as compared to other forms such as NO3--N.In aquatic environments,NH4+-N run off from farmland animal waste,agricultural fertilizers,domestic and industrial waste water are the major sources of ammonium for aquatic plants and could accumulate to toxic levels.At sufficient supplies,ammonium promotes plant growth and development.Though an important resource,NH4+-N is toxic when its concentrations exceed plant requirement.In Aquatic macrophytes grow in environments where ammonium can be available at quantitatively contrasting concentrations around both roots and shoots.The objective of this study was to assess the performance differences of aquatic macrophytes under different ammonium concentrations using laboratory treatments.In our study,we selected four(low,medium,high and control)different ammonium dosing at 0mg/L,0.1mg/L,15mg/L and 50mg/L.Ceratophyllwm demersum,Vallisneria natans and Potamogeton maackianus were cultured independently in improved Hoagland solution containing the four NH4+-N doses.To investigate the impacts of different concentrations of ammonium on these three species we measured the following parameters;chlorophyll a and b,proteins,chlorophyll fluorescence,free amino acids and soluble sugars.A similar trend was observed in all the three species-an increase in ammonium concentration led to a significant decrease of Chlorophyll a and b,soluble sugars and chlorophyll fluorescence while at the same time caused a remarkable increase in free amino acids and protein contents.A general observation indicates that high ammonium contents within the water column causes toxicity to aquatic macrophytes,ultimately influencing plant metabolism and photosynthesis as illustrated by shifts in the investigated parameters.Conclusions made from this study may help ecologists in macrophyte management for water restoration.