UPTAKE OF NITRATE-NITROGEN BY BLUEBERRY PLANTS

Kinetic parameters of the uptake of nitrate-nitrogen (NO3-N) by rabbiteye blueberry plants (Vaccinium ashei Reade cv. Tifblue) were studied. Plants were grown in nitrogen (N)-free nutrient solution for three days and then transferred to nutrient solutions that contained various concentrations of NO3-N. The rate of uptake of NO3-N was maximal 24 hr after exposure to nitrate at 0.2 mM and lower concentrations, whereas it was maximal after 8 hr at 0.4 mM NO3-N. Net uptake of NO3-N exhibited saturation-type kinetics over a range of concentrations of NO3-N in the nutrient medium of 0.0125 to 0.2 mM from zero hr to 28 hr. Vmax values 8 hr and 24 hr after the start of exposure to NO3-N were 1.58 and 1.75 mu mol/(g root fresh weight)/hr, respectively.