Department of Botany, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Plant Biol (Stuttg). 2012 Jan;14(1):118-28. doi: 10.1111/j.1438-8677.2011.00473.x. Epub 2011 May 18.
Using chlorophyll (chl) fluorescence imaging, we studied the effect of mild (MiDS), moderate (MoDS) and severe (SDS) drought stress on photosystem II (PSII) photochemistry of 4-week-old Arabidopsis thaliana. Spatio-temporal heterogeneity in all chl fluorescence parameters was maintained throughout water stress. After exposure to drought stress, maximum quantum yield of PSII photochemistry (F(v)/F(m)) and quantum efficiency of PSII photochemistry (Φ(PSΙΙ)) decreased less in the proximal (base) than in the distal (tip) leaf. The chl fluorescence parameter F(v) /F(m) decreased less after MoDS than MiDS. Under MoDS, the antioxidant mechanism of A. thaliana leaves seemed to be sufficient in scavenging reactive oxygen species, as evident by the decreased lipid peroxidation, the more excitation energy dissipated by non-photochemical quenching (NPQ) and decreased excitation pressure (1-q(p)). Arabidopsis leaves appear to function normally under MoDS, but do not seem to have particular metabolic tolerance mechanisms under MiDS and SDS, as revealed by the level of lipid peroxidation and decreased quantum yield for dissipation after down-regulation in PSII (Φ(NPQ)), indicating that energy dissipation by down-regulation did not function and electron transport (ETR) was depressed. The simultaneous increased quantum yield of non-regulated energy dissipation (Φ(NO)) indicated that both the photochemical energy conversion and protective regulatory mechanism were insufficient. The non-uniform photosynthetic pattern under drought stress may reflect different zones of leaf anatomy and mesophyll development. The data demonstrate that the effect of different degrees of drought stress on A. thaliana leaves show spatio-temporal heterogeneity, implying that common single time point or single point leaf analyses are inadequate.
利用叶绿素（chl）荧光成像，我们研究了轻度（MiDS）、中度（MoDS）和重度（SDS）干旱胁迫对 4 周龄拟南芥 PSII 光化学的影响。在整个水分胁迫过程中，所有 chl 荧光参数的时空异质性得以维持。在暴露于干旱胁迫后，PSII 光化学的最大量子产量（F(v)/F(m)）和 PSII 光化学的量子效率（Φ(PSΙΙ)）在近端（基部）叶片比在远端（尖端）叶片下降得更少。MoDS 后，chl 荧光参数 F(v) /F(m) 的下降幅度小于 MiDS。在 MoDS 下，拟南芥叶片的抗氧化机制似乎足以清除活性氧，这表现为脂质过氧化程度降低、非光化学猝灭（NPQ）更多地耗散激发能以及激发压力（1-q(p)）降低。拟南芥叶片在 MoDS 下似乎正常运作，但在 MiDS 和 SDS 下似乎没有特定的代谢耐受机制，这表现为脂质过氧化水平和 PSII 下调后的量子产量耗散（Φ(NPQ)）降低，表明通过下调耗散的能量传递（ETR）受到抑制。非调节能量耗散的量子产量（Φ(NO)）的同时增加表明，光化学能量转换和保护调节机制都不足。干旱胁迫下的非均匀光合作用模式可能反映了叶片解剖结构和叶肉发育的不同区域。这些数据表明，不同程度干旱胁迫对拟南芥叶片的影响表现出时空异质性，暗示常见的单一时间点或单点叶片分析是不够的。
