PDF(Pubmed)
Abstract：
Photosystem II (PSII) functions were investigated in basil (Ocimum basilicum L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS) conditions. Under MiDS, SA-sprayed leaves retained significantly higher (+36%) chlorophyll content compared to NS, SA-sprayed leaves. PSII efficiency in SA-sprayed leaves under NS conditions, evaluated at both low light (LL, 200 μmol photons m-2 s-1) and high light (HL, 900 μmol photons m-2 s-1), increased significantly with a parallel significant decrease in the excitation pressure at PSII (1-qL) and the excess excitation energy (EXC). This enhancement of PSII efficiency under NS conditions was induced by the mechanism of non-photochemical quenching (NPQ) that reduced singlet oxygen (1O2) production, as indicated by the reduced quantum yield of non-regulated energy loss in PSII (ΦNO). Under MiDS, the thylakoid structure of water-sprayed leaves appeared slightly dilated, and the efficiency of PSII declined, compared to NS conditions. In contrast, the thylakoid structure of SA-sprayed leaves did not change under MiDS, while PSII functionality was retained, similar to NS plants at HL. This was due to the photoprotective heat dissipation by NPQ, which was sufficient to retain the same percentage of open PSII reaction centers (qp), as in NS conditions and HL. We suggest that the redox status of the plastoquinone pool (qp) under MiDS and HL initiated the acclimation response to MiDS in SA-sprayed leaves, which retained the same electron transport rate (ETR) with control plants. Foliar spray of SA could be considered as a method to improve PSII efficiency in basil plants under NS conditions, at both LL and HL, while under MiDS and HL conditions, basil plants could retain PSII efficiency similar to control plants.
摘要：
在非胁迫（NS）或轻度干旱胁迫（MiDS）条件下，在用1mM水杨酸（SA）喷洒的罗勒（OcullbasilumL.）植物中研究了光系统II（PSII）功能。在MiDS下,与NS相比，SA喷雾的叶片保留了显着更高的叶绿素含量（36％），SA喷洒的叶子。NS条件下SA喷雾叶片的PSII效率，在两个弱光下评估(LL，200μmol光子m-2s-1)和强光(HL，900μmol光子m-2s-1)，随着PSII激发压力（1-qL）和过量激发能量（EXC）的平行显着降低，显着增加。在NS条件下PSII效率的提高是由减少单线态氧（1O2）产生的非光化学猝灭（NPQ）机制引起的。如PSII（ΦNO）中未调节能量损失的量子产率降低所示。在MiDS下,喷水叶片的类囊体结构出现轻微扩张，PSII的效率下降了，与NS条件相比。相比之下,在MiDS下，SA喷雾叶片的类囊体结构没有变化，虽然PSII功能被保留，类似于HL的NS植物。这是由于NPQ的光保护散热，这足以保留相同百分比的开放PSII反应中心(qp)，如在NS条件和HL中。我们建议，在MiDS和HL下，质体醌池（qp）的氧化还原状态引发了对SA喷雾叶片中MiDS的适应反应，与对照植物保持相同的电子传输速率（ETR）。SA的叶面喷雾可以被认为是在NS条件下提高罗勒植物PSII效率的方法。在LL和HL，在MiDS和HL条件下，罗勒植物可以保持与对照植物相似的PSII效率。
