Studies showed that elevated [CO2] would improve photosynthetic rates and enhance yields of rice;however,few studies have focused on the response of rice lodging,which is a major cause of cereal yield loss and quality reduction,under elevated [CO2].In this study,we examined the effects of elevated [CO2] on stem and root lodging using 4 rice cultivars(86Y8,japonica hybrid;LYP9,2-line indica hybrid;variety 9311,type of indica inbred rice,and SY63,3-line indica hybrid) grown under two [CO2] levels:400 and 680 μmol mol-1.Our results indicated that under elevated [CO2],the stem-lodging risk(SLR) of 9311 decreased,while in SY63 the SLR increased,86Y8 and LYP9 were not significantly affected;the risk of root lodging was reduced for all cultivars,because root biomass(instead of root number) and bending strength were increased significantly,and then the increase of anti-lodging ability is far higher than that of self-weight mass moment for all cultivars.These findings suggested that higher [CO2] can enhance the risk of stem-lodging for cultivars with strong-[CO2]-responses,but may not aggravate the root lodging for all rice cultivars. Studies showed that elevated [CO2] would improve photosynthetic rates and enhance yields of rice; however, few studies have focused on the response of rice lodging, which is a major cause of cereal yield loss and quality reduction, under elevated [CO2] .In this study, we examined the effects of elevated [CO2] on stem and root lodging using 4 rice cultivars (86Y8, japonica hybrid; LYP9,2-line indica hybrid; variety 9311, type of indica inbred rice, and SY63,3-line indica hybrid) grown under two [CO2] levels: 400 and 680 μmol mol-1.Our results indicated that under elevated [CO2], the stem-lodging risk (SLR) of 9311 decreased, while in SY63 the SLR increased, 86Y8 and LYP9 were not significantly affected; the risk of root lodging was reduced for all cultivars, because root biomass (instead of root number) and bending strength were increased significantly, and then the increase of anti-lodging ability is far higher than that of self- weight mass moment for all cultivars. these findings suggested that higher [CO 2] can enhance the risk of stem-lodging for cultivars with strong- [CO2] -responses, but may not aggravate the root lodging for all rice cultivars.