CO2浓度升高条件下水稻蒸腾与N吸收的关系

利用FACE（Free Air Carbon Dioxide Enrichment）平台技术，用水培试验研究了低氮（14 mg/L）和高氮（28 mg/L）水平下，大气CO2浓度升高条件下水稻蒸腾与N吸收速率的相关关系。结果表明，在CO2浓度升高条件下，水稻生物量增加了36%（低N）和29%（高N）；总吸N量也增加达7%（低N） 和5%（高N）；而总蒸腾量减少28%（低N）和10%（高N）。由于促进更多分蘖的发生，高CO2浓度使分蘖期水稻平均N吸收速率提高了31%～156%（低N）和19%～87%（高N），在其他时期无明显影响；而高CO2浓度对水稻平均蒸腾速率的影响主要表现在抽穗到灌浆末期。在对照条件下，平均蒸腾速率和平均N吸收速率呈显著正相关；但在CO2浓度升高条件下，两者相关关系不显著。说明人们所推测的“蒸腾效应”——高CO2浓度条件下降低了的蒸腾作用并非影响水稻N吸收的关键因素。

Relations Between Transpiration and N Uptake of Rice Grown in Elevated Air Carbon Dioxide Concentration

Correlation between transpiration and N uptake rate of rice at low N (LN, 14 mg/L) and high N (HN, 28 mg/L) in solution culture was studied under ambient air and elevated atmospheric p CO₂ (Ambient+200 μmol/mol) by the China FACE (Free-Air CO₂ Enrichment). Elevated p CO₂ increased rice biomass and total N uptake significantly by 36% and 7% at LN, 29% and 5% at HN, respectively, while decreased total amount of transpiration by 28% at LN and 10% at HN. Elevated p CO₂ stimulated average N uptake rate at the tillering stage as the result of enhanced occurrence of tillers. However, the significant effect of elevated p CO₂ on average transpiration rate was only observed from the panicle initiation to late filling stage. The positive correlation between transpiration rate and N uptake rate was significant at Ambient but not elevated p CO2, indicating that declined transpiration caused by CO₂ enrichment may not be the key factor affecting N uptake.