Samborska Izabela A, Kalaji Hazem M, Sieczko Leszek, Goltsev Vasilij, Borucki Wojciech, Jajoo Anjana
Department of Plant Physiology, Faculty of Agriculture and Biology, Warsaw University of Life Sciences WULS-SGGW, 159 Nowoursynowska, 02-776 Warsaw, Poland.
Department of Experimental Statistics and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences WULS-SGGW, 159 Nowoursynowska, 02-776 Warsaw, Poland.
Funct Plant Biol. 2018 May;45(6):668-679. doi: 10.1071/FP17241.
Magnesium (Mg) is one of the significant macronutrients which is involved in the structural stabilisation of plant tissues and many enzymes such as PSII. The latter efficiency and performance were analysed, using chlorophyll (Chl) a fluorescence induction kinetics and microscopic images, to detect the changes in structure and function of photosynthetic apparatus of radish plants grown under Mg deficiency (Mgdef). Plants grown under Mgdef showed less PSII connectivity and fewer active primary electron acceptors (QA) oxidizing reaction centres than control plants. Confocal and electron microscopy analyses showed an increased amount of starch in chloroplasts, and 3,3'-diaminobenzidine (DAB)-uptake method revealed higher H2O2 accumulation under Mgdef. Prominent changes in the Chl a fluorescence parameters such as dissipated energy flux per reaction centre (DIo/RC), relative variable fluorescence at 150μs (Vl), and the sum of the partial driving forces for the events involved in OJIP fluorescence rise (DFabs) were observed under Mg deficiency. The latter also significantly affected some other parameters such as dissipated energy fluxes per cross-section (DIo/CSo), performance index for energy conservation from photons absorbed by PSII antenna until the reduction of PSI acceptors (PItotal), and relative variable fluorescence at 300μs (Vk). This work emphasises the use of chlorophyll fluorescence in combination with microscopic and statistical analyses to diagnose the effects of nutrients deficiency stress on plants at an early stage of its development as demonstrated for the example of Mgdef. Due to the short growth period and simple cultivation conditions of radish plant we recommend it as a new standard (model) plant to study nutrients deficiency and changes in plant photosynthetic efficiency under stress conditions.
镁（Mg）是重要的大量营养素之一，参与植物组织的结构稳定以及许多酶（如光系统II）的作用。利用叶绿素（Chl）a荧光诱导动力学和显微图像分析了后者的效率和性能，以检测在缺镁（Mgdef）条件下生长的萝卜植株光合机构结构和功能的变化。与对照植株相比，在Mgdef条件下生长的植株光系统II的连接性较低，氧化反应中心的活性初级电子受体（QA）较少。共聚焦显微镜和电子显微镜分析显示叶绿体中淀粉含量增加，3,3'-二氨基联苯胺（DAB）摄取法显示在Mgdef条件下过氧化氢积累更多。在缺镁条件下，观察到叶绿素a荧光参数有显著变化，如每个反应中心的耗散能量通量（DIo/RC）、150μs时的相对可变荧光（Vl）以及OJIP荧光上升过程中相关事件的部分驱动力之和（DFabs）。后者还显著影响了其他一些参数，如每截面的耗散能量通量（DIo/CSo）、从光系统II天线吸收光子到光系统I受体还原的能量守恒性能指数（PItotal）以及300μs时的相对可变荧光（Vk）。这项工作强调了结合叶绿素荧光与显微镜和统计分析，在植物发育早期诊断营养缺乏胁迫对植物的影响，就像以Mgdef为例所展示的那样。由于萝卜植株生长周期短且栽培条件简单，我们推荐将其作为研究胁迫条件下营养缺乏和植物光合效率变化的新的标准（模式）植物。
