Inhibitory Effects of Ammoniacal Nitrogen on Growth of Radish Plants. I. Characterization of Toxic Effects of NH4+ on Growth and its Alleviation by NO3−1

Abstract

Growth of radish ( Raphanus sativus L.) was inhibited by NH 4 as the source of N at concentrations from 1 to 240 ppm N. Higher levels of free NH 4 accumulated in the plants as a result of NH 4 nutrition. Nitrate equivalent to 10% or more of the NH 4 concentration alleviated the inhibitor effects of NH 4 on growth and also decreased the NH 4 content of the plants. Five cultivars of radish responded similarly. Ammonium was also harmful for growth of etiolated seedlings, but NO 3 did not reverse the inhibitory effects of NH 4 .