Spiral down: Rice plants adopt helical root growth under ammonium stress (Plant J.)

While ammonium ions (NH₄⁺) serve as important sources of nitrogen nutrition, higher concentrations are toxic and inhibit plant growth and development. In an attempt to understand how roots of rice plant adapt to high concentrations of NH₄⁺, Jia and colleagues found the roots coil and adopt a helical growth pattern at their tips. Experiments indicated this to be due to loss of gravitropism and it correlated with enhanced NH₄⁺ uptake and the associated proton efflux and acidification of local medium. Detailed investigation of root auxin levels suggested that an asymmetric auxin distribution to one side of the root may result in the coiling pattern. Pharmacological studies too implicated an important role for auxin transport and signaling in promoting the helical growth of roots. Interestingly, Arabidopsis thaliana roots grown in medium with high NH₄⁺ did not show the helical growth, suggesting it to be a particular adaptation in rice plants. (Summary by Pavithran Narayanan @pavi_narayanan) Plant J. 10.1111/tpj.14978