Abstract: A japonica rice variety Wuxiangjing 14 was grown under ambient(AMB) or elevated CO₂(FACE,AMB + 200 μmol/mol) conitions and supplied with three levels of nitrogen: low level(LN,15 g/m²),normal level(NN,25 g /m²,similar to the level recommended to local farmers) and high level(HN,35 g/m²) to investigate the effect of elevated CO₂ and N supply on endopeptidase(EP) activity and the specific activity in the flag and the second leaves from the top of rice.As compared with AMB,FACE significantly increased EP activity in the flag and the second leaves at 10 days after heading(DAH) and 20 DAH,as well as EP activity in the second leaves at heading.However,EP activity in the flag leaves at maturity was greatly reduced under FACE.FACE obviously increased the specific activity in the flag and the second leaves at 10,20 DAH and maturity,together with the specific activity in the second leaves at heading.In general,CO2 enrichment-induced changes in both EP activity and specific activity were larger at 10 and 20 DAH than at heading and maturity.EP activity at early filling stage decreased greatly with increasing N supply,while it showed adverse trends at late filling stages.The specific activity decreased with increasing N supply at all sampling stages,with CO2 enrichment-induced decreases being larger at early than at late filling stages.Compared with AMB,FACE significantly decreased the content of soluble protein in the flag and the second leaves at 10,20 DAH and maturity,and CO₂ enrichment-induced changes in the content of soluble protein significantly decreased with increasing N supply.Soluble protein contents were correlated positively with EP activity in the flag and the second leaves at the maturity stage,while it showed adverse trends at the other sampling stages.This suggested that the CO2 enrichment-induced reduction in soluble protein content in leaves at the filling stage closely linked with corresponding changes in EP activity at elevated CO₂.

Key words: free air carbon dioxide enrichment, rice, endopeptidase, nitrogen, soluble protein

摘要： 利用农田开放式空气CO2浓度增高 (free air CO2 enrichment，FACE) 系统，CO2浓度设正常CO2 (ambient, AMB) 和高CO2 (FACE，AMB + 200 μmol/mol) 2个水平，施N量设低氮 (LN，15 g/m2，以纯氮计)、中氮 (NN，25 g/m2)和高氮 (HN，35 g / m2) 3个水平，对水稻品种武香粳14结实期剑叶和倒2叶的内肽酶活力变化情况进行了研究。结果表明: 1) 同AMB相比，FACE处理使剑叶抽穗后10 d、20 d以及倒2叶抽穗到抽穗后20 d内肽酶活力明显提高，但使剑叶成熟期内肽酶活力明显下降；使剑叶抽穗后10 d、20 d和成熟期以及倒2叶抽穗到成熟期内肽酶比活力明显提高；FACE对抽穗后10 d、20 d叶片内肽酶活力和比活力影响较大，而对抽穗期和成熟期的影响较小。同LN相比，HN使灌浆前期叶片内肽酶活力明显降低，灌浆中后期则呈增加趋势；HN降低了叶片各期内肽酶比活力，灌浆前期降幅大于后期。 2) 同AMB相比，FACE使叶片抽穗后10 d至成熟期可溶性蛋白含量明显降低；同LN相比，HN明显减缓FACE处理对抽穗后10 d至成熟期功能叶片可溶性蛋白含量的影响。 3）除成熟期叶片可溶性蛋白含量与内肽酶活力呈正相关外，结实期剑叶及倒2叶可溶性蛋白含量与对应时期内肽酶活力呈显著负相关。上述结果说明，FACE处理下水稻剑叶及倒2叶结实中后期可溶性蛋白含量明显下降与结实期叶片内肽酶活力的变化关系密切。

关键词: 开放式空气二氧化碳浓度增高, 水稻, 内肽酶, 氮肥, 可溶性蛋白