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Genetic canalization of nutrient resorption: evidence from a widespread grass under effective salt stress

L L LiuiD, Wenyi Sheng, Huijiaq Song, Cui WangiD, Na Li, Lele Lin, Yaolin GuoiD, Ning DUiD, Weihua GuoiD

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Abstract

Nutrient resorption is a key plant strategy for nutrient conservation, yet whether it responds plastically to non-nutrient stressors such as salinity remains unresolved. Using a common garden experiment with 110 genotypes of the cosmopolitan grass Phragmites australis, we first established that the imposed salinity treatment induced strong multi-level stress responses: above-ground biomass declined by >60%, sodium accumulated 3- to 5-fold across all leaf stages, and 484 metabolites showed significant differential accumulation, including canonical markers of osmotic and oxidative stress. Against this backdrop of confirmed stress, we found that nutrient resorption efficiency (NuRE) remained largely unaffected by salinity. Instead, NuRE was strongly correlated with phylogeographic lineage, ecotype, and latitude of origin, demonstrating evolutionary canalization rather than short-term acclimation. Element-specific regulatory patterns were also evident: while phosphorus resorption followed concentration-dependent control regardless of stress, nitrogen control was disrupted under salinity, and potassium resorption showed no such dependence. Our findings reveal that intraspecific variation in nutrient resorption is predominantly shaped by historical adaptation and geographic context, not by plasticity to salinity. This genetic canalization of a key functional trait implies that predictions of nutrient cycling under global change must account for the phylogeographic composition of plant populations.

In-depth summary

Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 2 (21 Aug 2026) · CC BY 4.0

In 110 common-garden Phragmites australis genotypes, effective salt stress left N, P and K resorption efficiency largely unchanged; efficiency instead tracked phylogeographic lineage, ecotype and latitude.

Most resorption studies focus on nutrient limitation, so it remains unclear whether non-nutrient stressors such as salinity, a spreading global change factor on coasts and in arid lands, cause plastic resorption shifts or whether population history fixes the trait. By confirming multi-level salt stress in a globally sampled reed panel, this work tests whether genetic origin or plasticity explains intraspecific variation in nutrient conservation.

Key results

  1. ShownThe 1% NaCl treatment caused clear physiological stress. Above-ground biomass fell by more than 60%, leaf sodium rose at every senescence stage, and hundreds of metabolites shifted, including osmotic and oxidative stress markers.

    Biomass 835.7 ± 36.4 g (control) vs 310.4 ± 15.0 g (salt), Welch's t = 13.26, p < 0.001; leaf Na 475 to 1929 mg kg⁻¹ (green), 508 to 2027 (yellowing), 1379 to 3722 (litter), all p < 0.001; 484 of 3,413 metabolites differential; N,N-dimethylglycine log₂FC +1.04, sucrose 6-phosphate +2.93. · 3.1 Salt stress induces multi-level…; Figure legends

  2. ShownResorption efficiency of N, P and K differed strongly among phylogeographic groups. There was no salinity main effect and no group-by-salinity interaction, which fits genetic canalization better than plastic acclimation.

    Mixed models with genotype as a random effect: phylogeographic group p < 0.001 for N, P and K resorption; salinity and group × salinity terms non-significant. CN_N had the lowest N and P resorption; CN_N and CN_E had high K resorption; invasive EU_NA did not diverge from native EU. · 3.2 Nutrient resorption efficiency is…; 4.4 Ecological and evolutionary implications of…; Figure legends

  3. ShownWithin Chinese populations, source habitat shaped N and P resorption: coastal saltmarsh ecotypes were highest and inland plateau saltmarsh ecotypes lowest. Under salt, N resorption rose in saltmarsh ecotypes relative to freshwater ones.

    Ecotype effect p < 0.001 for N and P resorption efficiency, p = 0.694 for K; salinity × ecotype interaction for N resorption p = 0.038. · 3.2 Nutrient resorption efficiency is…

  4. ShownControl of resorption differed by element. Concentration control held for P in both treatments, applied to N only without salt, and was absent for K. Stoichiometric coupling and an 'inverted' limitation pattern (P and K recovered relatively more than N) held in both treatments.

    Green vs litter concentration, standardized major axis (SMA): N β > 1, p < 0.05 in control, p > 0.05 under salt; P β > 1, p < 0.05 in both; K p > 0.05 in both. N-P and N-K resorption efficiencies positively related in both treatments; log resorbed vs log green N:P and N:K slopes > 1; OLS slopes broadly concordant. · 3.3 Element-specific regulatory strategies…; 4.2 Divergent strategies control the resorption…; Figure legends

  5. SuggestedResorption of all three nutrients increased with the absolute latitude of population origin. Latitude explained more variance than green-leaf nutrient concentrations or stoichiometry.

    Mixed models with phylogeographic group as a random intercept found significant positive latitude relationships for N, P and K resorption efficiency; glmm.hp hierarchical partitioning of marginal R² ranked latitude above concentration and stoichiometry for each element (Table 1; coefficients not given in main text). · 3.4 Latitudinal variation reflects macro-scale…; 4.3 Latitudinal gradient in resorption reflects…; Tables

Methods, data and reproducibility

Each of 110 reed genotypes was grown in paired control and 1% NaCl barrels in a common garden. Green leaves and senesced litter were assayed for elements, and carbon-standardized nutrient resorption efficiency (NuRE) was analyzed with linear mixed models, standardized major axis regression and variance partitioning, alongside untargeted leaf metabolomics.

  • Reed genotypes grown in paired control and 1% NaCl barrels in a Shandong, China common garden, drawn from genetically defined lineages AU, EU, EU_NA, NA, CN_N and CN_E · Phragmites australis (common reed) · n = 110 genotypes · 10.5281/zenodo.18321077
  • Chinese populations grouped by source habitat into freshwater wetland, coastal saltmarsh and inland plateau saltmarsh ecotypes · Phragmites australis · n = subset of the 110 genotypes (assignments in Table S1)
  • Green leaves (July 11, 2024) and senesced litter (December 4, 2024) used to compute N, P and K resorption efficiency · Phragmites australis
  • Leaf concentrations of 11 elements (C, N, P, K, Cu, Zn, Fe, Mn, Mg, Si, Na) in green, yellowing and senesced leaves · Phragmites australis · n = 11 elements across three leaf stages
  • Untargeted leaf metabolome by UPLC-QTOF mass spectrometry in positive and negative ion modes, salt vs control · Phragmites australis · n = 3,413 metabolites
  • Above-ground biomass at final harvest, control vs salt · Phragmites australis · n = 106 per group
Methods & tools
Waters Acquity I-Class PLUS UHPLC with Xevo G2-XS QTOF mass spectrometer, Progenesis QI with METLIN database annotation, ICP-OES (Thermo iCAP Pro) and ICP-MS (PerkinElmer NexION 1000G), UNICUBE elemental analyzer (C and N), limma (empirical Bayes differential accumulation), OPLS-DA and PERMANOVA, lme4 (linear mixed-effects models), emmeans (Tukey HSD post hoc tests), smatr (standardized major axis regression), glmm.hp (hierarchical variance partitioning), vegan and FactoMineR (PCA), ggplot2 and patchwork
Software & environment
R version 4.3.0 with vegan, FactoMineR, lme4, emmeans, smatr, glmm.hp, ggplot2 and patchwork; Progenesis QI for metabolomic peak processing.
Reproducibility gaps
Only the R version is given (no package versions or container). Genotype origins and lineage or ecotype assignments are in supplementary Table S1, and Table 1 R² values are not reproduced in the main text.
Limitations (6)
  • No nutrient-addition treatment was included, so nutrient limitation control was inferred only indirectly from resorbed nutrient ratios. The authors call for future designs that combine nutrient additions with salt stress. · stated by the authors
  • Salt was applied as a short-term shock (two NaCl additions in June of one season). The authors note that chronic, multi-year stress might trigger resorption responses this design would not capture. · stated by the authors
  • Ecotype classification was applied only to Chinese populations because habitat records for non-Chinese collections were insufficient, so ecotype contrasts leave out all non-Chinese genotypes. · stated by the authors
  • Continuous growth and leaf-tip abscission ruled out a mass-loss correction factor, so resorption relied on a carbon-basis (FCMB) adjustment rather than mass-based estimates. · stated by the authors
  • Canalization rests on non-significant salinity terms, without reported effect sizes, confidence intervals or equivalence tests. With one barrel per genotype per treatment at a single site and season, small plastic shifts may go undetected. · noted in this summary
  • Glutathione is described as significantly downregulated at log₂FC –0.27. That is below the |log₂ fold change| > 1 cutoff used to define the 484 differential metabolites, an inconsistency the text does not explain. · noted in this summary

Read this if you study nutrient resorption, salinity responses or intraspecific trait variation in wetland plants and want a multi-lineage common-garden test of plasticity versus genetic canalization in Phragmites.

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