Shanghai Key Lab of Protected Horticulture Technology, Horticultural Research Institute, Shanghai Academy of Agricultural Science, Shanghai, 201106, China.
Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agricultural, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
BMC Plant Biol. 2018 Sep 4;18(1):180. doi: 10.1186/s12870-018-1393-3.
Plants often suffer from hypoxic stress during waterlogging and hydroponic culturing. This study investigated the response of cucumber (Cucumis sativus L.) plant growth parameters, leaf photosynthesis, chlorophyll fluorescence, fast chlorophyll a fluorescence transient (OJIP), and fruit quality parameters to hypoxic stress alleviated by exogenous calcium. During the fruiting period, cucumber plants were exposed to hypoxia and hypoxia + Ca treatment (4 mM Ca) for 9 d.
Exogenous calcium application enhanced the biomass and fruit quality of hypoxic stressed cucumber and also increased the net photosynthesis rate, stomatal conductance, intercellular CO concentration, maximum quantum efficiency of photosystem II photochemistry, actual photochemical efficiency of PSII, photochemical quenching coefficient, and non-photochemical quenching coefficient. Additionally, measurement of chlorophyll a fluorescence transients showed the positive K- and L-bands were more pronounced in leaves treated with hypoxia compared with those with hypoxia + Ca, indicating that hypoxic treatment induced uncoupling of the oxygen-evolving complex and inhibited electron transport beyond plastoquinone pool (Q, Q) including possible constraints on the reduction of end electron acceptors of photosystem I. Exogenous calcium can reduce these stress-induced damages in cucumber.
This research focused the effect of exogenous calcium on cucumber photosynthesis during the fruiting period under hypoxic stress. Hypoxic stress might impair the photosynthetic electron-transport chain from the donor side of PSII up to the reduction of end acceptors of PSI, and exogenous calcium enhanced electron transport capacity and reduced hypoxic damage of cucumber leaves.
植物在水淹和水培过程中经常遭受缺氧胁迫。本研究调查了外源钙缓解缺氧胁迫对黄瓜（Cucumis sativus L.）植物生长参数、叶片光合作用、叶绿素荧光、快速叶绿素 a 荧光瞬变（OJIP）和果实品质参数的影响。在结果期，黄瓜植株在缺氧和缺氧+Ca 处理（4 mM Ca）下暴露 9 天。
外源钙的应用增强了缺氧胁迫下黄瓜的生物量和果实品质，同时提高了净光合速率、气孔导度、胞间 CO 浓度、光系统 II 光化学最大量子效率、PSII 实际光化学效率、光化学猝灭系数和非光化学猝灭系数。此外，叶绿素 a 荧光瞬变的测量表明，与缺氧+Ca 处理相比，缺氧处理下叶片的 K-和 L-带更为明显，表明缺氧处理诱导了放氧复合物的解偶联，并抑制了电子传递超越质体醌池（Q，Q），包括对光系统 I 的末端电子受体的还原的可能限制。外源钙可以减轻黄瓜的这些胁迫诱导损伤。
本研究重点研究了外源钙在黄瓜结果期缺氧胁迫下对光合作用的影响。缺氧胁迫可能会损害 PSII 供体侧到 PSI 末端受体还原的光合作用电子传递链，外源钙增强了电子传递能力，减轻了黄瓜叶片的缺氧损伤。
