氮肥运筹对孕穗期受渍冬小麦旗叶叶绿素荧光与籽粒灌浆特性的影响

以小麦品种皖麦54为试验材料，研究不同氮肥运筹对孕穗期受渍冬小麦旗叶叶绿素荧光特性的影响。结果表明，孕穗期小麦旗叶叶绿素含量最高，随后下降，至成熟期降到最低；渍水处理叶绿素含量下降幅度高于对照处理。对照处理孕穗期后叶绿素荧光参数F_v/F_m、F_v/F_o和q_p随小麦生育期的推进呈先增加后降低的变化趋势，于渍水处理孕穗期后第11~20天达到最高峰，NPQ呈先降低再升高的趋势。孕穗期渍水7 d后F_v/F_m、F_v/F_o和q_p均呈“低–高–低”的变化趋势，与对照相比，F_v/F_m低1.8%~2.3%，F_v/F_o低8.0%~10.9%，Φ_PSII则显著低于对照。基肥30%+拔节肥50%+孕穗肥20%(N4)处理生育后期旗叶叶绿素含量显著高于全部氮肥基施(N1)处理，而F_v/F_o、F_v/F_m和q_p显著高于N1和基肥70%+拔节肥30%(N2)处理。叶绿素含量与F_v/F_m、q_p和Φ_PSII呈显著正相关，与NPQ呈显著负相关。ETR-PAR响应曲线的拟合结果表明，孕穗期渍水7 d小麦生育后期旗叶ETR_max、α和E_k值较对照降低。N4的旗叶ETR_max、α和E_k均高于N1和N2。孕穗期渍水7 d条件下不同氮肥运筹方式间各叶绿素荧光参数变异系数高于对照，氮肥的补偿效应较对照明显。氮肥后移运筹方式显著减轻渍水逆境对光合器官的破坏，使小麦生育后期功能叶具有较强的光捕获能力和光化学效率，改善了旗叶光合性能，使灌浆期延长，平均灌浆速率提高，从而较氮肥前移处理显著提高小麦千粒重。

Effects of Nitrogen Fertilization on Chlorophyll Fluorescence Parameters of Flag Leaf and Grain Filling in Winter Wheat Suffered Waterlogging at Booting Stage

Waterlogging has great influence on yield of winter wheat in some areas of China.Nitrogen(N) application is believed to be able to improve photosynthesis of flag leaf and increase final yield.To understand the response of chlorophyll fluorescence parameters of wheat flag leaf to waterlogging stress at booting stage and the effect of N fertilization,we carried out a field experiment from autumn of 2008 to summer of 2010 using winter wheat cultivar "Wanmai 54".The waterlogging stress was imposed for 7 d at booting stage.Four N treatments were designed for waterlogging stress and the control(normal watering) of which N application rate was 240 kg ha-1 in all treatments but with different proportions at land preparation,jointing,and booting stages.The results showed that the maximum chlorophyll content of flag leaves occurred at the booting stage.Under normal watering condition,Fv/Fm,Fv/Fo,and qp showed "high-low" variation,and the maximum values were observed between May 3 and May 11.However,under waterlogging stress at booting stage,Fv/Fm,Fv/Fo,and qp showed "low-high-low" curve.Compared to control treatment,waterlogging at booting stage significantly decreased Fv/Fm,Fv/Fo,qp,and ΦPSII(P<0.05),and NPQ significantly increased(P<0.05).With the delay of N fertilization,Fv/Fm,Fv/Fo,qp,and ΦPSII increased significantly compared to the forward N fertilization treatments.Postpone of N supply improved photosynthetic capacity by increasing photosynthetic pigment contents,and enhancing photosynthetic efficiency under water deficit.The chlorophyll content was positively correlated with Fv/Fm,qp,and ΦPSII,(P<0.05),but negatively correlated relationship with NPQ(P<0.01).From the chlorophyll fluorescence rapid light curves,we found that,compared to normal watering,waterlogging stress at booting stage significantly decreased the maximal relative electron transport rate(ETRmax),initial slope(α),and half saturation point of light intensity(Ek).Postpone of N fertilizer application alleviated the photodamage to PSΙΙ caused by water stress,and the compensation effect of late N fertilization occurred earlier than that of early N fertilization,which resulted in longer filling period,higher mean filling rate,and ultimately increased 1000-grain weight.