Phenotypic plasticity and integration synergistically enhance plant adaptability to flooding and nitrogen stresses

Abstract

Aims

Plants respond to stress gradients by modifying various aspects of their morphology, physiology, architecture, allocation and mycorrhizal fungi. Yet, understanding how plants adapt to resource stress requires a comprehensive, integrated perspective that considers not only the consistency and variability of individual trait adjustments, but also the interplay between two key mechanisms: phenotypic plasticity (the direction and magnitude of trait adjustment) and phenotypic integration (the degree and pattern of trait covariation). Despite their importance, the coordination of these mechanisms in driving adaptive responses remains poorly understood.

Methods

To address these gaps, we measured the adjustment of 27 above- and below-ground traits across three dominant species (Cynodon dactylon, Xanthium strumarium, and Bidens tripartita), and explored trait networks, and the relationship between phenotypic plasticity and phenotypic integration in response to flooding and/or nitrogen in riparian habitats on the Three Gorges Reservoir area, China.

Results

The results show that both flooding and nitrogen stress induced shifts in species traits towards more acquisitive strategy, characterized by larger leaves, higher leaf nutrient concentrations, finer roots, larger specific root lengths, greater branching intensity, and elevated carboxylate concentrations. Flooding altered the hub trait with the highest centrality in the trait network from root branching intensity to leaf phosphorus content, while nitrogen stress shifted the hub trait from leaf area to root phosphorus content. Furthermore, a positive correlation was observed between phenotypic plasticity and integration, indicating that higher plasticity of functional traits facilitated better integration with other traits under flooding and nitrogen stress.

Conclusions

These findings suggest that plants exhibit more acquisitive traits in habitats experiencing flooding and/or nitrogen stress. Furthermore, a comprehensive assessment of phenotypic plasticity and its integration under compound stresses underscores the critical role of synergies between plasticity and integration in enhancing plant adaptability to environmental changes.