In order to reveal the effects of low night temperature on chlorophyll content and PS Ⅱ activity in different genotypes tomatoes leaves. The changes of chlorophyll content and chlorophyll fluorescence parameters in chilling-tolerant wild tomato LA 1777 and chilling-sensitive tomato Moneymaker under short-time 15℃(control) , 9℃ and 6℃ night temperature were studied. The results showed that the chlorophyll a, b content and chlorophyll a/b in two genotypes tomato leaves were significantly decreased under low night temperature stress, and the chlorophyll a and b content in Moneymaker significantly decreased than control after 1 d low night temperature treated. The Fo and NPQ increased in two tomatoes leaves under low night temperature, however, Fv/Fm,Φ>PS Ⅱ , ETR and qP were decreased significantly after low night temperature treated. Only NPQ in two tomatoes had the same trend, other fluorescence parameters in Moneymaker leaves had greater changed scale than LA 1777. The results showed that PS Ⅱ activity and electron transfer in cold-sensitive tomato leaves were influenced under low night temperature, and PS Ⅱ activity decreased significantly, but its decline scale was lower in cold-tolerant tomato.%为了明确不同基因型番茄叶片光系统Ⅱ(PSⅡ)活性对夜间低温逆境的响应.以耐低温野生番茄(Lycopersicon hirstum)LA1777和低温敏感型番茄(Lycopersicon esculentum Mill.)Moneymaker为试材,研究短期夜间15℃(对照)、9℃和6℃对不同基因型番茄叶片的叶绿素含量和叶绿素荧光参数的影响.结果表明:夜间低温下两种类型番茄幼苗叶片的叶绿素a、b含量及叶绿素a/b值均随着温度降低而呈下降趋势,夜间低温处理1d后,Moneymaker的叶绿素a和b含量均显著低于对照.夜间低温增加了番茄叶片的Fo(初始荧光)和NPQ(非光化学猝灭系数),显著降低了Fv/Fm(原初光能效率)、φPSⅡ(实际光化学量子效率)、ETR(电子传递速率)和qP(光化学猝灭系数).其中,除NPQ在两番茄叶片的变化趋势相似外,Moneymaker叶片的变化幅度均大于LA1777.这表明夜间低温显著影响了低温敏感番茄叶片PSⅡ反应中心和电子传递,显著降低了PSⅡ的活性,而对耐低温野生番茄PSⅡ活性影响较小.
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