Influence of soil oxidation-reduction potential and salinity on nutrition, N-15 uptake, and growth of Spartina patens

Nutrition, photosynthesis, and growth responses of Spartina patens to various intensities of sediment reduction (redox potentials, Eh) ranging between -115 mV to +475 mV and/or salinity of < 1 and 6 ppt were evaluated under controlled environmental conditions. Reduction in soil Eh to -115 mV seemed to have little effect on net photosynthesis, but 6 ppt salinity combined with low Eh significantly decreased net photosynthesis, indicating the adverse effects of combined low Eh and salinity on gas exchange functioning. The treatments showed striking differences in concentration of nutrients in the plants. In each Eh treatment, N content in the plants was low under 6 ppt salinity compared to the < 1 ppt treatment. N content and N-15 concentration in the plant also decreased as the soil Eh decreased. Data indicated that uptake of N was inhibited by low Eh due to reduced ability of roots to take up nitrogen and/or poor physical growth of roots. Plant Fe and Mn content increased considerably at low Eh treatments. However, salinity did not show consistent influence on Fe and Mn content of tissue.