摘要： 为明确桑树在不同氮形态下光合能力差异以及桑树对不同氮形态的需求规律，以1年生桑树实生苗为试验材料，研究了在硝态氮（NO₃^--N）、铵态氮（NH₄⁺-N）以及硝酸铵（NH₄NO₃）（氮素浓度均为7.5 mmol/L）处理下桑树叶片的叶绿素荧光特性。结果表明，桑树叶片在NH₄⁺-N下的PSⅡ光化学活性、电子传递速率和光能利用能力明显低于NO₃^--N和NH₄NO₃处理，而NO₃^--N和NH₄NO₃处理之间无明显差异。NH₄⁺-N处理下桑树叶片的V_J和V_I均较NO₃^--N和NH₄NO₃处理明显增加，即PSⅡ反应中心受体侧电子Q_A向Q_B传递速率较低，但此时桑树叶片的S_m和N却明显高于NO₃^--N和NH₄NO₃处理，说明导致NH₄⁺-N处理下桑树叶片PSⅡ受体侧电子传递能力降低的原因直接与Q_B功能的降低有关。另外，NH₄⁺-N处理下桑树叶片的V_K和V_L也明显低于NO₃^--N和NH₄NO₃处理，说明桑树叶片OEC活性的抑制与类囊体膜结构的稳定性降低也是导致其叶片PSⅡ反应中心光化学活性在NH₄⁺-N处理下降低的重要原因。

关键词: 桑树, 氮形态, 叶绿素荧光, PSⅡ

Abstract: In order to determine the photosynthetic capacity and requirement of mulberry for different nitrogen forms,one year old of mulberry seedlings as experimental materials,the chlorophyll fluorescence characteristics of mulberry leaves was studied under three nitrogen forms,in which nitrogen concentration was 7.5 mmol/L with nitrate nitrogen (NO₃^--N),ammonium nitrogen (NH₄⁺-N)and ammonium nitrate (NH₄NO₃).The results showed that the photochemical activity,electron transfer rate and light energy utilization of mulberry leaves in PS Ⅱ under NH₄⁺-N were significantly lower than that of NH₄NO₃ and NO₃^--N,while there was no significant differences between NH₄NO₃ and NO₃^--N.The V_J and V_I of mulberry leaves were significantly increased by NH₄⁺-N treatment,that was,Q_A to Q_B electronic transmission rate of PS Ⅱ electronic receptor side were lower.while,the S_m and N were significantly higher than those of NH₄NO₃ and NO₃^--N,which showed that the lower the electron transfer ability of PS Ⅱcould be related with capacity of receptor side of Q_B treated by NH₄⁺-N.In addition,V_K and V_L of mulberry leaf under NH₄⁺-N treatment was also lower than that of NO₃^--N and NH₄NO₃,which suggested that the suppressed OEC activity and decreased thylakoid membrane structure stability were the important reasons for reducing photochemical activity in the leaves of PS Ⅱ reaction centers under the NH₄⁺-N treatment.

Key words: Mulberry, Nitrogen form, Chlorophyll fluorescence characteristics, PS Ⅱ

中图分类号: 

• Q945.79

• S143.1