Denitrification on plants in nutrient solution culture

Spring wheat was grown in aerated and unaerated, complete and potassium deficient nutrient solution to study the influence of these factors on denitrification. Denitrification was determined by the acetylene inhibition method. When plants were pregrown in aerated nutrient solution and subsequently placed in a fresh unaerated nutrient solution, the oxygen content of the fresh solution disappeared later than at pregrowth in unaerated nutrient solution. N 2 O production set in earlier with plants pregrown in unaerated medium. The more rapid decline of oxygen and the faster denitrification were due to higher numbers of bacteria, including denitrifiers, on roots pregrown in unaerated medium. Interruption of aeration caused an increase in bacterial number within 24 hours to the level of the continuously unaerated treatment. Apart from the root quantity per pot the denitrification potential of the roots played an important role in total denitrification. By our definition, denitrification potential represented the N 2 O production of 1 g excised roots over 4 hours under anaerobic conditions at unlimited nitrate supply. The denitrification potential of roots grown in unaerated nutrient solution exceeded that of roots cultivated in aerated medium. Also at potassium deficiency the number of total bacteria and denitrifiers as well as root respiration increased resulting in a higher denitrification potential.