Abstract: In order to clarify the influence of biochar on rice root and yield under the background of increasing atmospheric CO2 concentration, the free-air carbon dioxide enrichment(FACE) was used to study the Jijing 88 rice. The experimental included 4 treatments: atmospheric CO2 concentration without biochar(CK), atmospheric CO2 concentration with 20g biochar per kilogram of dry soil(NB), high concentration CO2(550µmol·mol−1) without biochar(CN), and high-concentration CO2 with 20g biochar per kilogram of dry soil(CB), samples at the tillering stage, jointing stage, heading stage, and mature stage were taken to determine root morphology and physiological indicators, and yield at the mature stage was measured and analyzed. The results show that the single factors and mutual treatment have increased the total root length, total root surface area and root shoot ratio of rice root morphological indexes, CN treatment reduced the root dry weight by 39.24% at the tillering stage, CB treatment had extremely significant interaction effect on total root length and total root surface area in all experimental periods; the physiological index of rice root system responded positively to single factors and interaction treatment, CB treatment increased root bleeding intensity by 148.10%, 34.21%, 6.13%, 40.43% in each test period, and the interaction effect on root absorption area was not significant; single factors and mutual treatment increased panicles per hill, grains per panicle and 1000 grain weight, CN and CB treatments had negative effects on seed setting rate, while the CB treatment increased the panicles per hill and 1000- grain weight by 0.11% and 3.39%, and the interaction effect did not reach a significant level. the results show that except CN treatment reduced the root dry weight at tillering stage, the effects of single factors and interaction treatment on rice root morphology and physiological indices were positive. The interaction treatment had a significant effect on root morphology, the effect on the physiological function of the root system was not significant, and the treatment increased the number of grains per panicle and reduced the seed setting rate.

Key words: CO2, Biochar, Rice, Root traits, Climate change