After a 6-week growth, the plants were removed, rinsed in distilled 

 water, blotted, and fresh weights determined. Analyses for nitrate 

 reductase (NR) , glutamic dehydrogenase (GDH) , endogenous NH^, NO3, ni- 

 trite (NO2) , and buffer-soluble protein were determined on fresh root 

 and shoot tissue. 



Fresh weights of roots and shoots (Table 11) indicated that more 

 growth occurred when ammonium was the nitrogen source. Periodic ana- 

 lysis of nutrient solutions indicated that some ammonium was produced 

 in the nonaerated nitrate cultures. This may have been beneficial 

 because ammonium ions were the preferred nitrogen source for uptake. 

 In associated studies when nutrient solutions were changed weekly to 

 minimize ammonification in solution, less fresh weight was produced 

 with nitrate-cultured plants. 



Table 11. Fresh weight of shoots and roots after a 6-week growth in 

 nitrogen and aeration treatments. 





Grams fresh wt/plant 





Treatment 



Aeration 



Shoots 



Roots 



Total 













Ammonium 



No 

 Yes 



3.50 

 3.20 



0.84 

 1.10 



4.35 

 4.30 



Nitrate 



No 

 Yes 



2.60 

 1.20 



0.90 

 0.55 



3.50 

 1.75 



Ammonium 



plus 

 Nitrate 



No 

 Yes 



3.40 

 2.30 



0.92 

 0.90 



4.32 

 3.20 













Appearance of the nitrate plants indicated more severe growth ab- 

 normalities than was evident from the weight data in Table 11. Newly 

 germinated plants placed in nitrate culture developed yellowish leaves 

 and growth rates were restricted for the first 3 to 4 weeks. In the 

 early stages of growth, roots of these plants were spindly and elong- 

 ated, resembling symptoms of nitrogen-deficient root growth. After 4 

 to 6 weeks approximately 40 percent of the plants grown in nitrate 

 cultures appeared to overcome these symptoms and began to develop 

 greener leaves and higher growth rates. 



46 



