Drought and shade conditions are factors of limiting maize (Zea mays L.) photosynthesis for high yield. In order to observe the responses of non-photochemical chlorophyll fluorescence quenching (qN) as well as the change courses and components of qN to drought and shade stresses, these parameters were measured in different treatments. The results showed that: (1) Drought and shade treatments markedly increased qNs and qNmax, which was non-photochemical quenching at the maximum and stable stage respectively, and decreased the quantum yield of PSII photochemistry (ΦPSⅡ). (2) The ratio of qNs to qNmax corresponded to the severity of stresses, and its changes between different treatments were similar to that of relative decrease of plant dry matter weight (RDDMW). (3) Drought and shade effected, to certain degree, the time and rate of qN to reach the maximum or stable stage (TqNmax, RqNmax, TqNs and RqNs). The most important parameter RqNs was lowest in the severe drought and shade treatments (DD and SS), lower in treatments of recovering from drought and shade conditions (DR and SR), and highest in control. The changes in RqNs were almost identical with that of plant dry matter weight. (4) The shade treatments mainly increased energy-dependent quenching (qE), however, drought treatments mainly increased quenching related to state transitions (qT).%干旱和光照不足是干扰玉米光合作用,进而影响玉米高产的重要限制因素.为了了解玉米叶绿素非光化学荧光猝灭(qN)对干旱和遮光逆境的反应,我们研究了qN的主要叶绿素荧光参数.结果表明:(1) 干旱和遮光处理显著增加了最大值时的qNmax和稳定态时的qNs,降低了PSⅡ电子传递的光量子产量(ΦPSⅡ).(2) qNs与qNmax的比值与逆境的严重程度相符合,它在各处理间的变化趋势与植株干物重减少的百分率(RDDMW)一致.(3) 干旱和遮光在一定程度上影响了qN到达最大值或稳定态的时间和速率.其中qN到达稳定态的速率(RqNs)是一个非常有意义的指标,它在严重的干旱(DD)和遮光(SS)处理下最低,在较轻的干旱(DR)和遮光(SR)处理下较低,在对照中最高.RqNs在各处理间的变化趋势与植株干物重基本一致.(4) 遮光处理主要增加与能量耗散有关的qN的快组分(qE),而干旱处理主要增加与状态转换有关的qN的中组分(qT).
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