Zoufan Parzhak, Zare Bavani Mohammad Reza, Tousi Saham, Rahnama Afrasyab
Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Department of Horticultural Science and Engineering, Faculty of Agriculture, Agricultural Sciences and Natural Resources University of Khuzestan, Mollasani, Iran.
Physiol Mol Biol Plants. 2023 Jan;29(1):145-157. doi: 10.1007/s12298-022-01271-8. Epub 2022 Dec 27.
Melatonin is a growth regulator that improves the growth and chlorophyll (chl) content in plants. This study aims to investigate the effect of melatonin pretreatment on chl synthesis and fluorescence parameters in exposed to cadmium (Cd). The 42-day-old plants were transferred to nutrient solutions containing 50 μM melatonin. After two days, some plants were exposed to 50 μM Cd. Eight days after Cd treatment, some indicators related to chl fluorescence and some biochemical parameters were measured. In this study, melatonin increased chl content and chl /pheophytin (pheo ) ratio, chlorophyllide (chlide ), porphyrin compounds, and 5-aminolevulinic acid (5-ALA) in the presence of Cd. However, it decreased chl /chlide ratio under these conditions. Whereas Cd treatment resulted in significant reductions in photochemical activity and electron transfer rate in PSII, melatonin improved photochemical efficiency of PSII by reducing the toxic effect of Cd on the activity of the oxygen evolving complex (OEC) on the electron donor site and reducing non-photochemical quenching (NPQ). Based on the results, it appears that melatonin can maintain the chl content of plants exposed to Cd by increasing the precursors of the chl biosynthesis pathway and reducing its degradation rate. These results may, at least in our experimental conditions, partly explain the reason for the improved yield and growth of Cd-exposed plants when pretreated with melatonin.
褪黑素是一种生长调节剂，可促进植物生长并提高其叶绿素（chl）含量。本研究旨在探讨褪黑素预处理对镉（Cd）胁迫下植物叶绿素合成及荧光参数的影响。将42日龄的植株转移至含有50 μM褪黑素的营养液中。两天后，部分植株暴露于50 μM Cd中。Cd处理8天后，测定了一些与叶绿素荧光相关的指标和一些生化参数。在本研究中，在Cd存在的情况下，褪黑素增加了叶绿素含量、叶绿素/脱镁叶绿素（pheo）比值、叶绿素酸酯（chlide）、卟啉化合物和5-氨基乙酰丙酸（5-ALA）。然而，在这些条件下，它降低了叶绿素/叶绿素酸酯比值。Cd处理导致PSII的光化学活性和电子传递速率显著降低，而褪黑素通过降低Cd对电子供体部位放氧复合体（OEC）活性的毒性作用和减少非光化学猝灭（NPQ），提高了PSII的光化学效率。基于这些结果，似乎褪黑素可以通过增加叶绿素生物合成途径的前体并降低其降解速率，来维持Cd胁迫下植物的叶绿素含量。至少在我们的实验条件下，这些结果可能部分解释了用褪黑素预处理时Cd胁迫下植物产量和生长改善的原因。
