Abstract:

【Objcetive】In view of the potential impacts of increasing atmospheric carbon dioxide (CO₂) concentration and air temperature, the dynamic effects of these two important environmental factors and their interaction on leaf chlorophyll contents and SPAD values of rice in field were studied.【Method】 By using T-FACE(Temperature-Free Air CO₂ Enrichment) facility, a high yield and excellent-quality japonica rice (Oryza sativa L.) Wuyunjing 23 was grown at two levels of CO₂ (ambient and elevated CO₂ concentration) and two temperature regimes (ambient and elevated temperature) in a field experiment. We measured leaf chlorophyll contents and SPAD values during the whole growth period of rice plants.【Result】Elevated CO₂ concentration increased chlorophyll a, b, a+b contents of rice on 41, 77 and 94 days after transplanting (DAT) , with the maximum increase of 6.4%. On the contrary, they were decreased by elevated CO₂ concentration on 110 and 119 DAT, with the maximum decrease of 5.4%. Due to the greater responses of chlorophyll b to CO₂ concentration than that of chlorophyll a, elevated CO₂ concentration decreased chlorophyll a/b ratio on 41, 77 and 94 DAT by 4.7%, 2.3% and 0.9%, but increased it on 110 and 119 DAT by 1.9% and 5.3%, respectively. No obvious effect of elevated CO₂ concentration on leaf SPAD values was detected in the early and middle growth stages. But elevated CO₂ concentration decreased leaf SPAD values by 3.5% (P=0.1) and 19.1% (P<0.01) on 110 and 119 DAT. 1℃increase in temperature on average had positive effects on chlorophyll a, b, a+b contents in each growth stage of rice, but negative effects were found on chlorophyll a/b ratio. In general, the magnitudes of variation induced by temperature were less than those by elevated CO₂ concentration. No obvious effect of temperature elevation on leaf SPAD values was detected in the early and middle growth stages. But temperature elevation deceased leaf SPAD values by 7.1% (P<0.01) and 14.8% (P<0.01) on 110 and 119 DAT, respectively. No CO₂-temperature interaction was detected for most of measured parameters, but significant CO₂- or temperature-growth stage interactions were found.【Conclusion】The results indicated that elevated CO₂ concentration favored the leaf chlorophyll formation of rice in the early and middle growth stages. But in the late growth stage, leaf chlorophyll contents and SPAD value declined, meanwhile chlorophyll a/b ration increased significantly. Such phenomenon of quick-leaf-senescence induced by elevated CO₂ concentration was identical under the two temperature regimes.

Key words: FACE (Free Air CO2 Enrichment), carbon dioxide, temperature, chlorophyll content, SPAD values

摘要：

目的 针对不断增高的大气二氧化碳(CO₂)浓度和温度,研究这两个重要环境因子及其互作对大田生长水稻叶片叶绿素含量和SPAD值的动态影响。方法 利用农田T-FACE(Temperature-Free Air CO₂ Enrichment)系统,以高产优质粳稻武运粳23为供试材料,设置两个CO₂浓度(环境CO₂浓度和高CO₂浓度)和两个温度处理(环境温度和高温),测定自然生长环境下水稻不同生育期叶片的叶绿素含量及SPAD值。结果 550 µmol/molCO₂浓度使水稻移栽后41、77、94 d叶绿素a,b和a+b含量均增加(最大增幅为6.4%),但移栽110、119 d后均减少(最大降幅为5.4%)。由于叶绿素b含量对CO₂较叶绿素a含量更敏感,故高CO₂浓度使移栽后41、77和94 d叶绿素a/b值均下降,降幅分别为4.7%、2.3%和0.9%,但移栽110和119 d后分别增加1.9%和5.3%;以上对CO₂的响应多达显著水平。对叶片SPAD值而言,高CO₂浓度对水稻生长前、中期的影响较小,但移栽110和119 d后分别下降3.5%(P=0.1)和19.1%(P<0.01)。大田生长期增温1℃,各期叶绿素a、b以及a+b含量多呈增加趋势,叶绿素a/b值表现相反,但总体上变幅小于CO₂效应;高温对水稻前、中期叶片SPAD的影响较小,但移栽110和119 d后SPAD值平均下降7.1%和14.8%,均达极显著水平。CO₂与温度处理对上述测定参数多无显著互作效应,但CO₂浓度、温度处理与生育期之间多存在明显的互作效应。结论 大气CO₂浓度增高有利于水稻生长前中期叶片叶绿素的形成,但生长后期叶绿素含量和SPAD值均明显下降且伴随叶绿素a/b值的显著升高,这种早衰现象在不同生长温度下趋势一致。

关键词: FACE（Free Air CO2 Enrichment）, 二氧化碳, 温度, 叶绿素含量, SPAD值