Stamelou Maria-Lavrentia, Sperdouli Ilektra, Pyrri Ioanna, Adamakis Ioannis-Dimosthenis S, Moustakas Michael
Section of Botany, Department of Biology, National and Kapodistrian University of Athens, GR-15784 Athens, Greece.
Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization-Demeter, Thermi, GR-57001 Thessaloniki, Greece.
Plants (Basel). 2021 Mar 10;10(3):521. doi: 10.3390/plants10030521.
, a fungal pathogen that causes gray mold, is damaging more than 200 plant species, and especially tomato. Photosystem II (PSII) responses in tomato ( L.) leaves to spore suspension application were evaluated by chlorophyll fluorescence imaging analysis. Hydrogen peroxide (HO) that was detected 30 min after application with an increasing trend up to 240 min, is possibly convening tolerance against at short-time exposure, but when increasing at relative longer exposure, is becoming a damaging molecule. In accordance, an enhanced photosystem II (PSII) functionality was observed 30 min after application of , with a higher fraction of absorbed light energy to be directed to photochemistry (Φ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in a significant decrease in the dissipated non-regulated energy (Φ), indicating a possible decreased singlet oxygen (O) formation, thus specifying a modified reactive oxygen species (ROS) homeostasis. Therefore, 30 min after application of spore suspension, before any visual symptoms appeared, defense response mechanisms were triggered, with PSII photochemistry to be adjusted by NPQ in a such way that PSII functionality to be enhanced, but being fully inhibited at the application spot and the adjacent area, after longer exposure (240 min). Hence, the response of tomato PSII to , indicates a hormetic temporal response in terms of "stress defense response" and "toxicity", expanding the features of hormesis to biotic factors also. The enhanced PSII functionality 30 min after application can possible be related with the need of an increased sugar production that is associated with a stronger plant defense potential through the induction of defense genes.
灰葡萄孢是一种引起灰霉病的真菌病原体，它能侵害200多种植物，尤其是番茄。通过叶绿素荧光成像分析评估了番茄（L.）叶片对灰葡萄孢孢子悬浮液处理的光系统II（PSII）反应。在接种后30分钟检测到过氧化氢（H₂O₂），其含量呈上升趋势直至240分钟，这可能在短时间暴露时赋予对灰葡萄孢的耐受性，但在相对较长时间暴露时增加，则会成为一种损伤分子。相应地，在接种灰葡萄孢后30分钟观察到光系统II（PSII）功能增强，有更高比例的吸收光能被导向光化学作用（ΦPSII）。光合作用非光化学猝灭（NPQ）的光保护机制同时增加，导致耗散的非调节能量（ΦNO）显著降低，这表明单线态氧（¹O₂）形成可能减少，从而说明了活性氧（ROS）内稳态的改变。因此，在接种灰葡萄孢孢子悬浮液30分钟后，在任何可见症状出现之前，防御反应机制就被触发，PSII光化学通过NPQ进行调节，使得PSII功能增强，但在较长时间暴露（240分钟）后，在接种点及其相邻区域被完全抑制。因此，番茄PSII对灰葡萄孢的反应，在“应激防御反应”和“毒性”方面表现出一种刺激效应的时间响应，将刺激效应的特征扩展到了生物因子。接种灰葡萄孢后30分钟PSII功能增强可能与增加糖分产生的需求有关，而糖分产生的增加与通过诱导防御基因而具有更强的植物防御潜力相关。
