3.2 Relative distribution change of N to
new-born tillers under
eCO2
Higher N application rate increased N content in both leaf and sheath,
regardless of CO2 condition (Fig. 2 A and B). However,
eCO2 reduced the N content consistently under all N
application rates, compared to the ambient CO2treatments. It is worthy to mention that under the ambient
CO2 condition, N content reached a plateau at the N10
treatment, whereas under the eCO2 it still increased at
the N15, regardless of tissue type (leaf or sheath). This further showed
that N application rate was more a constraint to rice growth at the
eCO2 than at the ambient CO2 condition.
Contrary to the reductions of N contents in the leaf and sheath of rice
plant, the new-born tillers under the eCO2 tended to
have higher N content than under the ambient CO2 (Fig.
2C). Further comparison of their relative changes clearly demonstrated,
contrasting to the dramatic decrements of N content in both leaf and
sheath, the new-born tillers under the eCO2 showed a
slight increment (Fig. 2D), suggesting distribution favored the new-born
tillers. A plausible explanation was that a higher proportion of N
distributed to the new-born tillers under eCO2 than
under ambient CO2 condition.