PDF(Pubmed)
Abstract：
Water deficit is the major stress factor magnified by climate change that causes the most reductions in plant productivity. Knowledge of photosystem II (PSII) response mechanisms underlying crop vulnerability to drought is critical to better understanding the consequences of climate change on crop plants. Salicylic acid (SA) application under drought stress may stimulate PSII function, although the exact mechanism remains essentially unclear. To reveal the PSII response mechanism of celery plants sprayed with water (WA) or SA, we employed chlorophyll fluorescence imaging analysis at 48 h, 96 h, and 192 h after watering. The results showed that up to 96 h after watering, the stroma lamellae of SA-sprayed leaves appeared dilated, and the efficiency of PSII declined, compared to WA-sprayed plants, which displayed a better PSII function. However, 192 h after watering, the stroma lamellae of SA-sprayed leaves was restored, while SA boosted chlorophyll synthesis, and by ameliorating the osmotic potential of celery plants, it resulted in higher relative leaf water content compared to WA-sprayed plants. SA, by acting as an antioxidant under drought stress, suppressed phototoxicity, thereby offering PSII photoprotection, together with enhanced effective quantum yield of PSII photochemistry (ΦPSII) and decreased quantity of singlet oxygen (1O2) generation compared to WA-sprayed plants. The PSII photoprotection mechanism induced by SA under drought stress was triggered by non-photochemical quenching (NPQ), which is a strategy to protect the chloroplast from photo-oxidative damage by dissipating the excess light energy as heat. This photoprotective mechanism, triggered by NPQ under drought stress, was adequate in keeping, especially in high-light conditions, an equal fraction of open PSII reaction centers (qp) as of non-stress conditions. Thus, under water deficit stress, SA activates a regulatory network of stress and light energy partitioning signaling that can mitigate, to an extent, the water deficit stress on PSII functioning.
摘要：
水分亏缺是气候变化放大的主要胁迫因素，导致植物生产力下降最多。了解作物易受干旱影响的光系统II（PSII）响应机制对于更好地了解气候变化对作物的影响至关重要。水杨酸（SA）在干旱胁迫下的施用可能会刺激PSII功能，尽管确切的机制仍不清楚。为了揭示水（WA）或SA喷洒芹菜植物的PSII响应机制，我们在48小时采用叶绿素荧光成像分析，96小时,浇水后192小时。结果表明，浇水后96h，SA喷雾叶片的基质薄片出现扩张，PSII的效率下降了，与西澳喷洒的植物相比，这显示了更好的PSII功能。然而,浇水后192小时，SA喷雾叶片的基质薄片被恢复，而SA促进叶绿素合成，通过改善芹菜植物的渗透势，与WA喷洒的植物相比，它导致相对叶片含水量更高。SA,通过在干旱胁迫下充当抗氧化剂，抑制光毒性，从而提供PSII光保护，与WA喷雾植物相比，PSII光化学（ΦPSII）的有效量子产率提高，单线态氧（1O2）的生成量减少。干旱胁迫下SA诱导的PSII光保护机制由非光化学猝灭(NPQ)触发,这是一种通过将多余的光能作为热量消散来保护叶绿体免受光氧化损伤的策略。这种光保护机制，在干旱胁迫下由NPQ引发，足够保持，尤其是在强光条件下，在非胁迫条件下，开放的PSII反应中心（qp）的比例相等。因此，在缺水胁迫下，SA激活压力和光能量分区信号的调节网络，可以减轻，在某种程度上,缺水对PSII功能的压力。
