AUTHOR=Kong Lingan , Sun Mingze , Wang Fahong , Liu Jia , Feng Bo , Si Jisheng , Zhang Bin , Li Shengdong , Li Huawei TITLE=Effects of high NH+4 on K+ uptake, culm mechanical strength and grain filling in wheat JOURNAL=Frontiers in Plant Science VOLUME=Volume 5 - 2014 YEAR=2014 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2014.00703 DOI=10.3389/fpls.2014.00703 ISSN=1664-462X ABSTRACT=

It is well established that a high external NH⁺₄ concentration depresses many processes in plant development, but the underlying mechanisms are still not well understood. To determine whether the negative effects of high levels of NH⁺₄ are related to competitive cation uptake, wheat was grown in a field with moderate (18 g N m⁻²) and high (30 g N m⁻²) supplies of NH⁺₄ in the presence or absence of additional K⁺ (6 g K₂O m⁻²) to examine culm mechanical strength, the main components of the vascular bundle, nitrogen (N) remobilization and the grain-filling rate. The results indicated that an excessive supply of NH⁺₄ significantly decreased culm mechanical strength, the cellulose and lignin contents of vascular bundles, the N remobilization efficiency (NRE) and the grain-filling rate compared with a moderate level of NH⁺₄. The additional provision of K⁺ considerably alleviated these negative effects of high NH⁺₄, resulting in a 19.41–26.95% increase in culm mechanical strength during grain filling and a 34.59% increase in the NRE. An assay using the scanning ion-selective electrode technique (SIET) showed that the net rate of transmembrane K⁺ influx decreased by 84.62%, and measurements using flame photometry demonstrated that the K⁺ content decreased by 36.13% in wheat plants subjected to high NH⁺₄. This study indicates that the effects of high NH⁺₄ on culm mechanical strength, cellulose and lignin contents, the NRE and the grain-filling rate are probably associated with inhibition of K⁺ uptake in wheat.