Uptake of ammonium‐nitrogen by blueberry plants

Abstract Blueberry plants (Vaccinium ashei Reade cv. Tifblue) and Citrus natsudaidai Hayata were compared in terms of their ability to regulate the uptake of ammonium‐nitrogen (NH4‐N). Plants of both species were grown in N‐free nutrient solutions for three days and then transferred to nutrient solutions that contained various concentrations of NH4‐N. Blueberry plants showed increases in rates of uptake of NH4‐N 8 to 24 h after application of NH4‐N. At concentrations of NH4‐N above 200 (μM, uptake rates decreased to the initial value 24 h after application of NH4‐N and then increased. By contrast, seedlings of Citrus natsudaidai showed constant rates of uptake of NH4‐N during the experiment. These results indicate that blueberry plants are able to repress the uptake of NH4‐N periodically when they are exposed to high concentrations of external NH4‐N, but not seedlings of Citrus natsudaidai.