Effect Of Elevated CO₂Concentration On Rice Lodging Resistance By FACE Study

The lodging is a common question in food production. In order to preciely predict the impacts of elevated carbon diocide concentration (E-CO2) on food security in near future, a systemic study is required for understanding the effects of E-CO2on lodging resistance of staple food crops. However, such study can only be conducted on the experimental platform with gas fumigation conditions that resemble natural field. Rice is one of the most important grain crops in the world. An FACE (Free Air CO2Enrichment) experiment was conducted in a rice field using unique FACE system in China in2013. Two Chinese rice cultivars, Wuyunjing23(conventional japonica rice) and II you084(super rice), were grown at ambient (A-CO2) or elevated [CO2](200ppm above ambient, E-CO2). The study determined the field lodging status, field breaking-resistant strength, lodging index, breaking-resestant strength of the basal internodes, bending moment, weight of internodes, weight per unit length, plant height, internode length, internode cross-sectional area, wall thickness, P, K and Si concentration of basal internodes, yield traits, etc. The aim of study was clear the change of rice lodging resistance and the possible reason under the environment of elevated [CO2].The results showed as follows:1. Wuyunjing23(WYJ23) was not lodged whether Ambient or FACE conditions at seed setting stage. Under Ambient conditions, lodging occur at32days after heading (DAH) for Ⅱ you084(Ⅱ Y084), the field lodging rate was51%,62%and100%at32,38DAH and grain maturity, respectively. However, under FACE conditions, only grain maturity was lodged and the lodging rate was12%.2. E-CO2increased field breaking-resistant strength per plant of WYJ23by39%,31%,25%,21%at10,25,40days after heading (DAH) and grain maturity, respectively, and II Y084was increased by26%,39%at10,25DAH, respectively, with the effects all reaching significant level. Similar treads were obseaved for the field breading-resistant strength per stem of the two cultivars.3. E-CO2reduced lodging index of basal internodes (the fifth, forth and third internodes from the top, the same below) of W YJ23by13～20%,10～18%,9～14%,19～29%at10,25,40DAH and grain maturity, respectively, and Ⅱ Y084was reduced by8～13%,10～12%,4～22%,9～16%respectively. For the majority of internodes, the effects of CO2reaching above0.1significant level.4. E-CO2increased breaking-resestant strength of basal internodes of WYJ23by7-22%,6～14%,6～12%,17～34%at10,25,40DAH and grain maturity, respectively, however, the effects of CO2was only significant at grain maturity. Ⅱ Y084was increased by6～15%,26～29%,20～45%,19～33%respectively, for the majority of internodes, the effects of CO2reaching significant or very significant level.5. The bending moment of basal internodes of WYJ23by E-CO2was not significant at10,25,40DAH and grain maturity. However, ⅡY084was increased by-7～-1%,10～13%,13～15%,13～16%respectively, the significant CO2effects were found for internodes investigated in addition to10DAH.6. E-CO2increased dry weight of basal internodes of WYJ23by2-22%,-9～6%,3～19%,20～53%at10,25,40DAH and grain maturity, respectively, and Ⅱ Y084was increased by20～29%,12～23%,30～34%,34～59%respectively. The effects of the last two periods was significant greater than the fiist two periods for intenodes investigated.7. E-CO2increased dry weight per unit length of basal internodes of WYJ23by22～28%,-1～11%,14～32%,29～45%at10,25,40DAH and grain maturity, respectively, for the majority of internodes, the effects of CO2reaching above0.1significant jlevel in addition to25DAH. Ⅱ Y084was increased by28～40%,27～28%,37～55%,29～39%respectively, for the majority of internodes, the effects of CO2reaching significant level in addition to10DAH. 8. Compared with A-CO2, E-CO2reduced plant height of WYJ23by3cm,2cm,2cm and2cm at10,25,40DAH and grain maturity, respectively, and the effects of E-CO2was significant at grain maturity. However,11Y084was increased by1cm,2cm,2cm and3cm respectively, and the effect of CO2was0.1significnat at grain maturity. Agree with plant weight, E-CO2slightly reduced the basal internote length of WYJ23at10,25,40DAH and grain maturity,ⅡY084was slightly increased, however, the effects of CO2were not statistically significant.9. Averaged across the two cultivars, cross-sectional area of basal internodes by E-CO2was not significant at25and40DAH, but E-CO2increased by10～21%at grain maturity. For the majority of internodes, the effects of CO2was significant at grain maturity. The increase of latter was due to long diameter (average by3～11%) and short diameter (average by5～11%) of basal internodes were significant increased.10. Averaged across the two cultivars, wall thickness of basal internodes by E-CO2was not significant at10and40DAH, but at grain maturity, E-CO2increased by8-～2%and10～20%to WYJ23and ⅡY084respectively. The effects of CO2was above0.1significant for two cultivars at grain maturity.11. Averaged across the two cultivars, E-CO2reduced P, K and Si concentration of basal internodes at25,40DAH and grain maturity. For the majority of internodes, the effects of CO2reaching significant or above0.1significant level.12. E-CO2increased grain yield by9%and36%to WYJ23and Ⅱ Y084respectively, the latter was very significant. The grain yield of Ⅱ Y084sharp increased mainly due to significant increased of panicle number per unit area (+16%) and filled grain percentage (+11%).13. There was significant interaction between CO2and cultivar for bending moment, plant height and grain yield during productive stage or rice.The above date showed that E-CO2will significant decrease risk of lodging during productive stage or rice on the middle of the century, it is mainly associated with breaking-resestant strength of the basal internodes significant enhanced, while the latter may be associated with increased of internode enrichment degree...