Nitrogen nutrition of Salvinia natans: Effects of inorganic nitrogen form on growth, morphology, nitrate reductase activity and uptake kinetics of ammonium and nitrate

作者：Jampeetong Arunothai^*; Brix Hans

来源：Aquatic Botany, 2009, 90(1): 67-73.

DOI：10.1016/j.aquabot.2008.06.005

• Salvinia natans
• Water fern
• Ammonium
• Nitrate
• Nitrogen uptake kinetics
• Nitrate reductase activity (NRA)
• Wetland plant
• Ammonium toxicity

In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO(3)(-), NH(4)( ), or both at equimolar concentrations (500 mu M). Plants supplied with only NO(3)(-) had lower growth rates (0.17 /- 0.01 g g(-1) d(-1)), shorter roots, smaller leaves with less chlorophyll than plants supplied with NH(4)( ) alone or in combination with NO(3)(-) (RGR = 0.28 /- 0.01 g g(-1) d(-1)). Ammonium was the preferred form of N taken up. The maximal rate of NH(4)( ) uptake (V(max)) was 6-14 times higher than the maximal uptake rate of NO(3)(-) and the minimum concentration for uptake (C(min)) was lower for NH(4)( ) than for NO(3)(-). Plants supplied with NO(3)(-) had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO(3)(-) was primarily reduced in the roots, but NRA levels were generally low (< 4 mu mol NO(2)(-) g(-1) DW h(-1)). Under natural growth conditions NH(4)( ) is probably the main N source for S. natans, but plants probably also exploit NO(3)(-) when NH(4)( ) concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH(4)( ) levels in the water, even though the uptake capacity for NO(3)(-) is reduced under these conditions.

• 出版日期2009-1