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作 者 ：苏秀荣¹;王秀峰²;杨凤娟²;魏珉²

期 刊 ：应用生态学报 2007年 18卷 07期 页码：1441-1446

关键词：黄瓜；

摘 要 ：研究了不同浓度NO₃^-胁迫对黄瓜幼苗叶片光合速率、PSⅡ光化学效率及光能分配的影响.结果表明，当NO₃^-浓度较低时（14～98 mmol·L^-1），适当增加NO₃^-浓度，可增强黄瓜幼苗叶片对光的捕获能力，促进光合作用.随着NO₃^-浓度的进一步增加（140～182 mmol·L^-1），PSⅡ光化学效率降低，电子传递受到抑制，净光合速率降低；吸收的光能中，通过天线色素的热耗散增加，用于光化学反应的能量降低，光化学效率下降.140和182 mmol·L^-1 NO₃^-处理黄瓜幼苗叶片6 d后净光合速率(P_n)极显著下降，分别比对照降低了35%和78%；PSⅡ最大光化学效率(F_v/F_m)、天线转化效率(F_v’/F_m’)、实际光化学效率(Φ_PSⅡ)、光化学猝灭系数(q_P)均低于对照，非光化学猝灭(NPQ)高于对照，激发能在两个光系统间的分配不平衡性(β/α-1)增大.高浓度NO₃^-处理的黄瓜幼苗叶片各荧光参数变化幅度比低浓度大.当光照增强时，高浓度NO₃^-胁迫下黄瓜幼苗叶片吸收的光能中应用于光化学反应的份额(P) 显著降低，天线热耗散的份额(D)显著增加. 天线热耗散是耗散过剩能量的主要途径.

Abstract:This paper studied the effects of different NO₃^- concentration on the photosynthetic rate, photochemical efficiency, and absorbed light energy allocation in cucumber seedling leaves. The results indicated that when the available NO₃^- concentration in the medium was low (14-98 mmol NO₃^-·L^-1),an appropriate supplement of NO₃^- could enhance the capability of cucumber leaves in capturing light energy, and promote the photosynthesis. However, with further increase of NO₃^-, the photochemical efficiency of PSⅡ decreased, electron transfer restrained, and net photosynthetic rate as well as the absorbed light energy used in photochemical reaction of PSⅡ decreased. At the same time, the light energy used in antenna heat dissipation increased,
while the photochemical efficiency decreased. After treated with 140 and 182 mmol NO₃^-·L^-1 for 6 days, the photosynthetic rate (P_n) was decreased by 35% and 78%, respectively, maximal PSⅡ efficiency at open centers in the absence of NPQ (F_v/F_m), antenna efficiency at open centers in the presence of NPQ(F_v’/F_m’), actual PSⅡ efficiency (Φ_PSⅡ) and photochemical quenching (q_P) were lower, non-photochemical quenching (NPQ) was higher, and the deviation from full balance between PSⅠ and PSⅡ (β/α-1) was improved significantly, compared with the control. The fluctuant ranges of these chlorophyll fluorescence parameters were increased at higher NO₃^- concentration, compared with those at lower NO₃^-concentration. The absorbed light energy allocated to the photochemical reaction of PSⅡ (P) was reduced by high light intensity and high NO₃^-concentration. Meanwhile, the proportion allocated in antenna heat dissipation (D) increased significantly. Antenna heat dissipation was the main way for excessive energy dissipation.

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