Inhibitory effects of aromatic acids on nitrogen uptake and transport in rice (Oryza sativa L.) plants cultured on hydroponics

Absrtact: The application of fresh wheat or barley straw often inhibits the growth and N uptake of paddy rice plants in the establishment phase. This inhibition is mainly attributed to the deficiency of available N in soil, resulting from a large N assimilation by soil microbes in soils supplied with straw (Rao and Mikkelsen 1976). In a previous report (Tanaka and Nishida 1996), we showed that the activity of¹⁵N uptake from¹⁵NH₄⁺ introduced into the soil decreased by straw application. We found the accumulation of some aromatic acids in soils to levels inhibitory to root elongation when fresh wheat straw was applied (Tanaka 1990; Tanaka et al. 1990). No attempt were made to investigate the effects of aromatic acids on N uptake by rice seedlings. Here we report on examination on whether aromatic acids such as 2-phenylpropanoic acid (2P), 3-phenylpropanoic acid (3P), and benzoic acid (BA), found in paddy soils, may inhibit N uptake and transport in rice plants.