Abstract: Human activities have intensified global nitrogen deposition, profoundly affecting plant community structure and ecological functions. Phragmites australis, a key wetland species, is widely distributed and ecologically important; however, the mechanisms underlying its long-term response to nitrogen deposition, and whether nitrogen-induced parental effect can be stably transmitted to offspring remain unclear. To address this, we conducted a greenhouse experiment involving 12 genotypes of P. australis to investigate the effects of simulated nitrogen deposition on parental phenotypes and transcriptomes, as well as the consequent effects on offspring growth. Our results indicated that parental simulated nitrogen deposition enhanced the adaptability of parental plants to high-nitrogen environments by modulating metabolic pathways and promoting increases in leaf area and biomass in most genotypes. The legacy effect (parental simulated nitrogen deposition only) and cumulative effect (continuous simulated nitrogen deposition) had only minor impact on offspring performance, with responses exhibiting genotype-specificity; only a few genotypes showed significant growth or reproductive advantages following parental simulated nitrogen deposition. These findings suggest that parental effect associated with nitrogen responses are difficult to transmit consistently to offspring at the population level. Consequently, under nitrogen deposition, the overall growth and clonal propagation of P. australis populations are unlikely to be significantly enhanced.

Key words: common reed, cumulative effect, genotypic variation, legacy effect, maternal effect, nitrogen deposition