Responsive characteristics of Flaveria bidentis epigenetic variation and phenotypic plasticity under different nitrogen treatments.
To clarify the effects of different nitrogen levels on Flaveria bidentis invasion, we simulated four nitrogen gradients of farmlands. Using the MSAP method, the DNA methylation variations and phenotypic plasticity responsive characteristics of the biomass, growth, and photosynthetic physiological indices of Flaveria bidentis were studied. The results showed that 18 pairs of primers amplified 690 MSAP bands and the percentage of primer polymorphism was 86.38%. The differences in the semi-methylation and total methylation levels were significant between the T2(275 kg.hm-2)and T3(375 kg.hm-2)treatments. The difference in the full-methylation level was significant between the CK and other treatments. The increasing nitrogen application rate significantly increased the biomass and root biomass allocation of Flaveria bidentis and promoted vegetative and reproductive growth as well as plant photosynthesis, but decreased the biomass allocation of the support structure. Under nitrogen treatment, the phenotypic plasticity index of flower buds, leaf area index, and root biomass of Flaveria bidentis were the highest, i.e., 0.824 7, 0.666 0, and 0.531 1, respectively. Whereas the phenotypic plasticity index of biomass allocation and photosynthetic physiological index were much lower, which may indicate that Flaveria bidentis adapts to nitrogen changes mainly by regulating its own nutrition, reproductive growth, and root biomass. The results of correlation analysis between phenotypic plasticity and epigenetic variation showed that a significant negative correlation existed between the semi-methylated level and the number of buds as well as root biomass, between the full-methylated level and plant height as well as the leaf area index, and also between the total methylated level and root biomass, while a significant positive correlation existed only between the total methylated level and leaf biomass.