Responses of rice (Oryza sativa) growth and its C, N and P composition to FACE (Free-air Carbon Dioxide Enrichment) and N,P fertilization.
XIE Zubin, ZHU Jianguo, ZHANG Yali, MA Hongliang, LIU Gang, HAN Yong,ZENG Qing and CAI Zucong (Key Laboratory of Material Cycling in Pedosphere, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008).
FACE (Free-air Carbon Dioxide Enrichment) was used to study the effects of elevated CO 2 on rice (Oryza sativa) growth,tissue C/N,N and P concentration and uptake at different development stages under two N and two P levels. Results showed that elevated CO 2 increased dry matter accumulation in rice stem, ear and root. Leaf dry matter was increased at tillering stage and no significant effect was found at jointing, heading and ripening stages. N concentration of stem and leaf was decreased. Ear N concentration at heading stage was increased but was decreased at ripening stage. No significant effect was found on root N concentration at tillering stage but root N concentration at jointing, heading and ripening was decreased. Leaf P concentration at jointing, heading and ripening was increased but no significant effect was found on P concentration in stem, ear and root. C content in various tissues changed unremarkably and the ratio of C over N (C/N) was increased. Elevated CO 2 significantly increased P uptake in aboveground tissues; and increased N uptake, but the difference was not statistically significant. N and P fertilization had no significant effect on various tissue dry biomass. Tissue N content at higher N fertilization was higher than at lower N fertilization but no such effect of P fertilization on tissue P content was found. At higher N fertilization, elevated CO 2 increased the ratio of below-ground biomass over above-ground biomass at ripening stage. Possible reasons are discussed for the differences of tissue N and P content and the ratio of below-ground biomass over above-ground biomass between elevated and ambient atmospheric CO 2 concentrations.