早熟桃夏季叶色转红过程中的光化学响应特征

比较研究了‘早美’和‘春蕾’2个早熟桃品种夏季叶色转红对太阳光能的利用和光系统Ⅱ的叶绿素荧光特征的影响。结果表明：早熟桃叶片色素组成的变化会显著影响其光合和叶绿素荧光特性。叶色转红后，早熟桃净光合速率（Pn）日均值、PSII最大光化学效率（Fv/Fm）、PSII实际光化学效率（ФPSII）均上升，无显著光抑制，而绿叶对照‘红花碧桃’的电子传递速率（ETR）、Fv／Fm和ФPSII值均显著下降，7月光合明显受抑制。叶色转红程度较深的‘早美’在夏季高温强光下表现优于‘春蕾’和对照。淬灭分析表明：叶片花色素苷的积累能在短时间内增加PSII天线色素吸收的光能用于光化学反应的份额（P）与用于反应中心热耗散的相对份额（D）。转红后的叶片光化学淬灭系数（qp）显著高于绿叶，PSII光化学效率较高，但耗散过剩激发能的能力显著低于绿叶对照。

Photochemical Response Characteristics of Early-Maturing Peach during Leaf Color Turned to Be Red in Summer

Taking two early-maturing peach cultivars ＇Zaomei＇ and ＇Chunlei＇ as materials, the changes of solar utilization and chlorophyll fluorescence characteristics of photosystem Ⅱ were studied during leaf discoloration period in summer. The results showed that, early-maturing peach had great changes in photosynthetic and chlorophyll fluorescence characteristics despite the strong differences in leaf pigment composition. Net photosynthetic rate （Pn）, PSII maximal photochemical efficiency （Fv/Fm） and PSII actual photochemical efficiency （ФPSII） of early-maturing peach increased, and there was no significantly photosynthetic inhibition during the experiment. While green leaf control ＇Honghuabitao＇ showed obvious photo inhibition in July, electron transport rate （ETR）, Fv/Fm and Ф PSII values decreased. ＇Zaomei＇, which was more intensely colored, was more adaptive to high temperature and strong light in summer than ＇Chunlei＇ and control. Chlorophyll fluorescence quenching analysis indicate that leaf anthocyanin accumulation lead to a transitory increase of relative share of photochemical reaction （P） and heat dissipation （D） from antenna pigment absorbed light. The reddened leaves had higher photochemical quenching coefficient （qp） than green leaves, and more effective PSII photochemical reactions. However, the lower non-photochemical quenching coefficient （NPQ） values shown by reddened leaves probably indicate a lower ability to dissipate safely excess photon energy than that of green leaves.