RESUMO
Rice (Oryza sativa) resistance is its ability to resist various stresses, the changes of which have important impacts on O. sativa yield security. However, the responses of O. sativa stress resistance to elevated atmospheric CO2 concentration and temperature are poorly understood. We conducted a field open top-chamber experiment with O. sativa (Nanjing 9108 and Jinxiangyu I) based on the CO2 and temperature automatic control platform. The experimental treatments included ambient CO2 concentration and temperature treatment (CK, control), elevated CO2 concentration treatment (C, CO2 concentration increase of 200 µmol·mol-1 above CK), elevated temperature treatment (T, temperature increase of 2 â above CK) and elevated CO2 concentration and temperature (CT, CO2 concentration increase of 200 µmol·mol-1 and temperature increase of 2 â above CK). At the critical growth stages of O. sativa, we measured superoxide dismutase activity, silica content, total flavanol content, malondialdehyde content, soluble sugar content, proline content, and soluble protein content by cutting the uppermost functional leaves. We obtained the rice stress resistance index (RSRI) by principal component analysis to analyze the differences in the composition of stress resistance indicators under different treatments. Considering the disease resistance of O. sativa, the spike neck blast disease was counted to verify the expression level of RSRI for O. sativa stress resistance at maturity stage. Results showed that at the elongation-booting stage, C and CT treatments significantly reduced the RSRI of Jinxiangyu I by 36.5% and 41.1%, respectively, compared with CK. T treatment significantly decreased the RSRI of the two varieties by 44.9% and 33.8%, respectively. The RSRI explained 71.9%-74.3% of the variation in the spike neck blast disease. Overall, the stress resistance of two O. sativa varieties were adversely affected by elevated temperature at the elongation-booting stage. There was an interactive effect of CO2 concentration and temperature on O. sativa stress resistance. Compared with Nanjing 9108, the stress resistance of Jinxiangyu I was more sensitive to elevated CO2 concentration.
Assuntos
Dióxido de Carbono , Resistência à Doença , Temperatura , Malondialdeído , Folhas de PlantaRESUMO
To examine the effects of elevated CO2 concentrations on chlorophyll fluorescence of rice leaf, a field experiment was conducted with automatic control system of CO2 concentration in open top-chambers (OTCs). There were three treatments, including atmospheric CO2 concentration (CK), CK+80 µmol·mol-1 CO2 (T1), and CK+200 µmol·mol-1 CO2 (T2). The fast chlorophyll fluorescence induction dynamic curves of flag leaves were measured using the plant efficiency analyzer at the main growth stages of rice. The results showed that T1 treatment significantly increased quantum yield for electron transfer (φEo), maximum photochemical efficiency (Fv/Fm), and performance index (PIABS), but decreased quantum yield for energy dissipation (φDo) at the flowe-ring, milk grain, ripening, and full ripeness stages. The values of φEo, Fv/Fm, and PIABS were increased by 7.3%-23.3%, 3.1%-7.1%, and 46.2%-93.0%, respectively. The φDo values were decreased by 10.3%-20.5%. T2 treatment significantly decreased φEo, Fv/Fm, PIABS by 68.7%, 41.4%, and 93.4%, respectively, but increased φDo by 78.4% at the jointing stage. T2 treatment significantly increased φEo, Fv/Fm, PIABS by 11.6%-19.8%, 4.8%-6.8%, and 53.0%-72.6%, respectively, and decreased φDo by 7.7%-19.4% at the flowering, milk grain, and ripening stages. Our results suggested that elevated CO2 concentration (80, 200 µmol·mol-1) would promote photosynthetic electron transport of PS2 in flag leaves of rice.