3.1 Interactive effects of eCO2and N application rate on
tillering
Compared with the ambient [CO2],
eCO2 significantly increased the number of tillers (Fig.
1A). In respect to N application, the number of tillers increased with N
application rate, with more enhancement at leaf-age six than at leaf-age
four. Under the higher N application, eCO2 stimulated
more tillers (Fig 1A). Tiller occurrence percentage and uniformity were
also enhanced by eCO2 at leaf-age four (Fig. 1B),
especially under eCO2 and higher N application.
Apparently, the tiller enhancement effect by eCO2depended on N application rate, indicating that the N availability
constrained tillering, especially under eCO2.
Similarly, eCO2 increased biomass more at the higher
than lower N application rate (Fig. 1C). Though N application promoted
biomass accumulation in both the ambient and eCO2conditions, the biomass accumulation reached a plateau at the N10
treatment under the ambient CO2 condition. At the N15
treatment, biomass still showed a significant increment under the
eCO2 condition (Fig. 1C). It can be concluded that
eCO2 promoted biomass accumulation, especially when
combined with higher N application rate.