Humic acid differentially improves nitrate kinetics under low‐ and high‐affinity systems and alters the expression of plasma membrane H+‐ATPases and nitrate transporters in rice |
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| Authors: | OCH Tavares LA Santos LM Ferreira MVL Sperandio JG da Rocha AC García LB Dobbss RLL Berbara SR de Souza MS Fernandes |
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| Affiliation: | 1. Plant Nutrition Laboratory, Department of Soils, Federal Rural University of Rio de Janeiro, Rio de Janeiro, Brazil;2. Soil Biology Laboratory, Department of Soils, Federal Rural University of Rio de Janeiro, Rio de Janeiro, Brazil;3. Environmental Microbiology and Biotechnology Laboratory, Vila Velha University, Vila Velha, Brazil;4. Plant Biochemistry Laboratory, Department of Chemistry, Federal Rural University of Rio de Janeiro, Rio de Janeiro, Brazil |
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| Abstract: | Humic acids (HAs) have a major effect on nutrient uptake, metabolism, growth and development in plants. Here, we evaluated the effect of HA pretreatment applied with a nutrient solution on the uptake kinetics of nitrate nitrogen (N‐NO3?) and the metabolism of nitrogen (N) in rice under conditions of high and low NO3? supply. In addition, the kinetic parameters of NO3? uptake, N metabolites, and nitrate transporters (NRTs) and the plasma membrane (PM) H+‐ATPase gene expression were examined. The plants were grown in a growth chamber with modified Hoagland and Arnon solution until 21 days after germination (DAG), and they were then transferred to a solution without N for 48 h and then to another solution without N and with and without the addition of HAs for another 48 h. After this period of N deprivation, the plants received new nutrient solutions containing 0.2 and 2.0 mM N‐NO3?. Treatment of rice plants with HA promoted the induction of the genes OsNRT2.1‐2.2/OsNAR2.1 and some isoforms PM H+‐ATPase in roots. The application of HAs differentially modified the parameters of the uptake kinetics of NO3? under both concentrations. When grown with 0.2 mM NO3?, the plants pretreated with HA had lower Km and Cmin values as well as a higher Vmax/Km ratio. When grown with 2 mM NO3?, the plants pretreated with HA had a higher Vmax value, a greater root and shoot mass, and a lower root/shoot ratio. The N fractions were also altered by pretreatment with HA, and a greater accumulation of NO3? and N‐amino was observed in the roots and shoots, respectively, of plants pretreated with HA. The results suggest that pretreatment with HA modifies root morphology and gene expression of PM H+‐ATPases and NO3? transporters, resulting in a greater efficiency of NO3? acquisition by high‐ and low‐affinity systems. |
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| Keywords: | H+‐ATPases humic acid nitrate nitrate transporters |
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