Abstract
Plant available nitrogen forms are nitrate and ammonium in most of non-fertilized soil. Many plant species show growth inhibition when they are supplied ammonium as sole nitrogen source. However, many plant species tend to preferentially take up ammonium when both nitrogen forms are available. Ammonium can be dominant nitrogen nutrition form in anaerobic paddy field and forest-floor ecosystems. Since ammonium nutrition does not require energy for reduction, it could be better nutrition than nitrate.
We compared the root architecture and shoot biomass of various Arabidopsis ecotypes on the medium containing ammonium as major nitrogen source in order to reveal the mechanism for efficient ammonium utilization in plant. As a result, we found that the growth of some ecotypes was not prevented by ammonium nutrition while that of other ecotypes was prevented. Ammonium sensitive ecotypes elongated primary root (PR) while tolerant ecotypes contracted PR. Recombinant inbred lines of two ecotypes were used for quantitative trait locus (QTL) analysis to identify the gene responsible for root development respond to ammonium supply.
