b. Experiment 2 . Plants were germinated and transferred to cul- 

 tures of either ammonium or nitrate (Table 1) . Both treatments were 

 nonaerated. The first 3-week growth occurred under growth chamber 

 conditions as previously described; because of a growth chamber mal- 

 function, plants were transferred to greenhouse conditions for the re- 

 maining 11 weeks. Nutrient solutions were changed every 2 weeks. At 

 10 weeks' growth, both ammonium and nitrate concentrations were increa- 

 sed to 8 millimoles (mM) for 1 week, and increased to the normal 4-mM 

 concentration for the last 3 weeks. At the end of 15 weeks' growth, ~ 

 plants were harvested, rinsed in distilled water, dried at 70° Celsius, 

 and weighed. Analyses for nitrogen (N) , phosphorus (P) , potassium (K) , 

 calcium (Ca) , sodium (Na] , magnesium (Mg) , copper (Cu) , iron (Fe) , 

 zinc (Zn) , and manganese (Mn) were performed by the Analytical Service 

 Laboratory, North Carolina State University, Soil Science Department 

 (Table 13) . 



Table 13. 



Dry weight and nutrient concentration after 14 weeks' 

 growth under nonaerated conditions. 



Treatment 



Dry wt 

 g/plant 



Nutrient Concentration 



N 



P 



K 



Na 



Ca 



Mg 



Zn 



Cu 



Fe 



Mn 





Cone 



9- 



Cone, ppm 





■ > 



























Ammonium 

 Shoots 

 Roots 



4.69 

 2.00 



2.10 



1.17 



0.41 

 0.31 



2.10 

 1.60 



2,43 

 1.94 



0.23 

 0.13 



0.08 

 0.10 



79 



13 



70 



79 



Nitrate 

 Shoots 

 Roots 



4.09 

 1.39 



1.42 

 1.02 



0.41 

 0.33 



1.29 

 1.80 



3.16 

 2.40 



0.37 

 0.13 



0.07 

 0.15 



71 



10 



58 



152 



























Nitrogen concentration of shoots and roots was highest for the 

 ammonium treatment, indicating a greater uptake. Of particular in- 

 terest are the differing sodium and potassium concentrations obtained 

 with the different nitrogen sources. Potassium concentration was high- 

 est with the ammonium treatment; sodium was highest with the nitrate 

 treatment. With other species, the presence of ammonium usually re- 

 sults in a lower potassium concentration. However, such studies are 

 not commonly conducted with the low ambient potassium-sodium ratio 

 (Table 1) used here. Calcium concentration in the shoots was greater 

 with the nitrate treatment although no difference was observed for 

 root tissue. In contrast, magnesium concentration of the shoots was 

 not affected by the nitrogen source; root magnesium was significantly 



49 



