Integrated Molecular Plant Physiology Research (IMPRES), Department of Biology, University of Antwerp, Belgium; Botany and Microbiology Department, Faculty of Science, Beni-Suef University, Beni-Suef, 62511, Egypt.
Integrated Molecular Plant Physiology Research (IMPRES), Department of Biology, University of Antwerp, Belgium; Center of Excellence Plants and Ecosystems (PLECO), Department of Biology, University of Antwerp, Belgium; Shanghai Center for Plant Stress Biology, Center of Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Environ Pollut. 2020 Mar;258:113705. doi: 10.1016/j.envpol.2019.113705. Epub 2019 Dec 5.
Heavy metal accumulation in agricultural land causes crop production losses worldwide. Metal homeostasis within cells is tightly regulated. However, homeostasis breakdown leads to accumulation of reactive oxygen species (ROS). Overall plant fitness under stressful environment is determined by coordination between roots and shoots. But little is known about organ specific responses to heavy metals, whether it depends on the metal category (redox or non-redox reactive) and if these responses are associated with heavy metal accumulation in each organ or there are driven by other signals. Maize seedlings were subjected to sub-lethal concentrations of four metals (Zn, Ni, Cd and Cu) individually, and were quantified for growth, ABA level, and redox alterations in roots, mature leaves (L1,2) and young leaves (L3,4) at 14 and 21 days after sowing (DAS). The treatments caused significant increase in endogenous metal levels in all organs but to different degrees, where roots showed the highest levels. Biomass was significantly reduced under heavy metal stress. Although old leaves accumulated less heavy metal content than root, the reduction in their biomass (FW) was more pronounced. Metal exposure triggered ABA accumulation and stomatal closure mainly in older leaves, which consequently reduced photosynthesis. Heavy metals induced oxidative stress in the maize organs, but to different degrees. Tocopherols, polyphenols and flavonoids increased specifically in the shoot under Zn, Ni and Cu, while under Cd treatment they played a minor role. Under Cu and Cd stress, superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR) activities were induced in the roots, however ascorbate peroxidase (APX) activity was only increased in the older leaves. Overall, it can be concluded that root and shoot organs specific responses to heavy metal toxicity are not only associated with heavy metal accumulation and they are specialized at the level of antioxidants to cope with.
重金属在农业土壤中的积累导致了全球范围内的作物减产。细胞内的金属内稳态受到严格调控。然而，内稳态的破坏会导致活性氧（ROS）的积累。在胁迫环境下，植物整体适应能力取决于根和地上部的协调。但是，对于重金属的器官特异性响应知之甚少，其是否取决于金属类别（氧化还原或非氧化还原反应性），以及这些响应是否与每个器官中的重金属积累有关，或者是否由其他信号驱动。本研究将玉米幼苗分别暴露于亚致死浓度的四种金属（Zn、Ni、Cd 和 Cu）中，在播种后 14 和 21 天（DAS）时，定量测定根、成熟叶片（L1、2）和幼叶（L3、4）中的生长、ABA 水平和氧化还原变化。结果表明，所有器官中的内源金属水平都显著增加，但程度不同，其中根中的金属水平最高。重金属胁迫下生物量显著减少。尽管老叶积累的重金属含量低于根，但它们的生物量（FW）减少更为明显。金属暴露主要在老叶中引发 ABA 积累和气孔关闭，从而降低光合作用。重金属在玉米器官中诱导氧化应激，但程度不同。在 Zn、Ni 和 Cu 处理下，生育酚、多酚和类黄酮特异性地在地上部增加，而在 Cd 处理下它们的作用较小。在 Cu 和 Cd 胁迫下，根中诱导了超氧化物歧化酶（SOD）和脱氢抗坏血酸还原酶（DHAR）活性，而在老叶中仅增加了抗坏血酸过氧化物酶（APX）活性。总之，可以得出结论，根和地上部器官对重金属毒性的特异性响应不仅与重金属积累有关，而且在抗氧化剂水平上具有特异性。
