ABSTRACT
NH4+ nutrition has emerged as an effective approach to generate salt tolerance in sorghum plants. Our hypothesis was that salt-tolerance mechanisms in NH4+-grown sorghum are related to rapid absorption and assimilation of NH4+ as well as favorable K+ uptake. Sorghum plants were grown in nutrient solutions containing NO3− or NH4+ and subjected to NaCl at 75 mM. Under control conditions, K+ uptake was more pronounced in NO3− than that of NH4+-fed plants. Under salinity, NH4+-grown plants showed lower Na+ and higher K+ contents than NO3–grown plants at 1 and 10 days after salt exposure, and thereby increased K+/Na+ ratio. The data indicate that NH4+ does not increase K+ uptake under salt stress conditions, but decrease the K+ efflux and maintain an elevated K+/Na+ ratio in tissues. In parallel, sorghum plants displayed elevated NH4+ uptake, evidenced by higher Vmax for NH4+, assimilating a higher amount of NH4+ into amino acids in roots; whereas NO3−-fed plants accumulated NH4+ in the shoot. In conclusion, NH4+-fed salt-stressed sorghum plants maintain favorable K+/Na+ homeostasis due to greater retention of K+ in tissues together with restricting control of Na+ accumulation and transport. S. bicolor face to NH4+ toxicity by activating mechanisms for rapid inorganic N-assimilation.
Acknowledgements
The Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Instituto Nacional de Ciência e Tecnologia em Salinidade (INCTSal) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for financial support.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary material
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