Effects Of Elevated CO₂ Concentration And High Temperature On The Growth Of Rice Root

To determine the effects of CO2 concentration and air temperature on the growth of rice root,a field cultivation and a hydroponic experiment were carried out in 2013 and 2014. T-FACE(heating and free-air carbon dioxide enrichment) technique was used to investigate the effects of elevated CO2 and high temperature supply on rice root morphology, root exudates and some root physiological activities.(1)Increases in atmospheric carbon dioxide concentration have been shown to increase rice root biomass significantly. It was increased by 50%, 37.2%, 37.7% at tillering, jointing and heading stages in the hydroponic experiment. In the field cultivation, the effects of CO2 enrichment on amounted to gains of root biomass of 50%, 32%, 28.6% for booting stage, milky stage, dough stage, respectively. The temperature treatments had no significantly effects on root biomass. In 2013, the result suggests that the positive effect of high concentration of CO2 tend to be weakened by high temperature. In 2014, the root biomass under elevated CO2 and temperature were similar to those observed at only CO2 enrichment.(2)The findings presented here indicate that CO2 enrichment have large positive effects on rice root morphology. The length, surface area, volume of rice root and tips number were significantly higher than that at ambient CO2. Significant changes in root morphology were found under elevated temperature at tillering stage. Total root length, root surface area,root volume have increased by 90%, 62%, 36%. Some parameters such as root length and the number of root tips have a negative responded under elevated temperature at heading stage. Fine root turnover accelerated by higher temperature, maybe one of the reasons of fine roots decreased. At tillering stage, we found a positive correlation between CO2 enrichment and higher temperature. Results at heading stage suggest that the limitation on root tips exposed to higher temperature can be mitigated by CO2 enrichment,(3)Elevated CO2 stimulated the root activity per plant, as total absorption area and active absorption area have increased significantly. During the early stage of rice growth, the active absorption area ratio was also significantly higher than that in ambient. The effects of elevated temperature was not significant. The field cultivation experiment, the root of 1-naphthylamine oxidation under higher CO2 concentration was significantly higher than other treatments, there was no difference among the other treatments.(4)Elevated CO2 and temperature treatments had no significantly effects on the C/N of root. The content of soluble sugar and soluble protein was not significantly affected.(5)Elevated CO2 increased the concentrations of the DOC content per plant. The high temperature had the promotion effect on TOC content and organic acid content in root exudates..