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The root nitrogen uptake response to partial nitrogen stress is related to previous nutritional status

Niu, Xiaoli, Hu, Tiantian, Zhang, Fucang, Duan, Aiwang, Zhang, Jiyang
Plant growth regulation 2019 v.87 no.1 pp. 55-67
containers, corn, nitrogen, nutrient solutions, nutrient use efficiency, nutritional status, root systems, seedlings
We investigated the dynamics and factors influencing the N uptake capacity in two sub-root systems of maize seedlings under partial N stress. Maize seedlings were grown in split-root containers containing nutrient solutions. Two N application conditions prior to partial N stress (full-strength N (4.0 mM): CP; N stress: SP) were considered. Thus, two experiments were conducted: (A) four treatments: CPNc, CPN₂, CPN₁ and CPN₀, in which half of the root system was exposed to 4.0 mM, 2 mM, 1 mM and 0 mM N (CPNc–c, CPN₂–₂, CPN₁–₁ and CPN₀–₀), respectively, and the other half received full-strength N (CPNc–c, CPN₂–c, CPN₁–c and CPN₀–c); (B) four treatments: SPNc, SPN₂, SPN₁ and SPN₀, in which both sub-root systems received 4.0 mM, 2 mM, 1 mM and 0 mM N for 6 days, respectively, after which half of the root system was maintained at original N level (SPNc–c, SPN₂–₂, SPN₁–₁ and SPN₀–₀) and the other half received full-strength N (SPNc–c, SPN₂–c, SPN₁–c and SPN₀–c). At 0.25 days after treatment (DAT), CPN₂–c and CPN₁–c enhanced N inflow rates (Iᵣₒₒₜ), whereas CPN₀–c decreased it by 27.3% compared with CPNc–c, Iᵣₒₒₜ in CPN₂–c, CPN₁–c and CPN₀–c was uniformly enhanced at 1 DAT, but were only enhanced in CPN₀–c at 5 DAT compared with CPNc–c. In contrast, SPN₁–c had a significantly increased Iᵣₒₒₜ by 10.52% compared with SPNc–c, although other treatments showed a negative effect on Iᵣₒₒₜ at 0.25 DAT. At 1 and 5 DAT, Iᵣₒₒₜ in SPN₂–c, SPN₂–₂, SPN₁–c, SPN₁–₁ and SPN₀–c were significantly lower than that in SPNc–c. Furthermore, CP significantly enhanced Iᵣₒₒₜ in non-stressed sub-roots compared with SP. Additionally, CPN₂ improved shoot dry mass and N use efficiency even under SPN₂. Thus, N uptake capacity in each sub-root zone varied not only depending on the severity and duration of the N stress, but was also related to the N status prior to partial N stress. Moreover, the occurrence and disappearance of the root compensatory effect were delayed with increasing N stress severity. A higher compensatory effect developed following CP, even under CPN₀.