Adaptational significance of variations in DNA methylation in clonal plant Hierochloe glabra (Poaceae) in heterogeneous habitats

As a prominent epigenetic modification, cytosine methylation may play a critical role in the adaptation of plants to different environments. The present study sought to investigate possible impacts of differential levels of nitrogen (N) supply on cytosine-methylation levels of a clonal plant, Hierochloe glabra Trin. (Poaceae). For this purpose, nitrate was applied at concentrations of 0, 0.15, 0.30 and 0.45 g N kg–1 soil, and ecologically important morphological traits were measured. The methylation-sensitive amplification polymorphism method was also conducted to analyse the variations in DNA cytosine methylation. Our results showed that N addition reduced CHG cytosine-methylation levels markedly compared with control plants growing in homogeneous pots (P = 0.026). No substantial differences were observed in morphological traits at the end of the growing stage, except for the highest ratio of leaf area to leaf dry mass in the medium-N patch (P = 0.008). However, significant linear regression relationships were found between cytosine-methylation levels and morphological traits, such as bud number and rhizome length and biomass. In conclusion, the higher cytosine-methylation level may activate asexual reproduction to produce more offspring and expand plant populations, possibly helping clonal plants to adapt to heterogeneous habitats.