Asaeda Takashi, Rahman Mizanur, Liping Xia, Schoelynck Jonas
Hydro Technology Institute Co, Ltd., Tokyo, Japan.
Research and Development Center, Ibaraki, Japan.
Front Plant Sci. 2022 May 16;13:855477. doi: 10.3389/fpls.2022.855477. eCollection 2022.
In vegetation management, understanding the condition of submerged plants is usually based on long-term growth monitoring. Reactive oxygen species (ROS) accumulate in organelles under environmental stress and are highly likely to be indicators of a plant's condition. However, this depends on the period of exposure to environmental stress, as environmental conditions are always changing in nature. Hydrogen peroxide (HO) is the most common ROS in organelles. The responses of submerged macrophytes, , to high light and iron (Fe) stressors were investigated by both laboratory experiments and natural river observation. Plants were incubated with combinations of 30-200 μmol m s of photosynthetically active radiation (PAR) intensity and 0-10 mg L Fe concentration in the media. We have measured HO, photosynthetic pigment concentrations, chlorophyll (Chl-a), chlorophyll (Chl-b), carotenoid (CAR), Indole-3-acetic acid (IAA) concentrations of leaf tissues, the antioxidant activity of catalase (CAT), ascorbic peroxidase (APX), peroxidase (POD), the maximal quantum yield of PSII (F F ), and the shoot growth rate (SGR). The HO concentration gradually increased with Fe concentration in the media, except at very low concentrations and at an increased PAR intensity. However, with extremely high PAR or Fe concentrations, first the chlorophyll contents and then the HO concentration prominently declined, followed by SGR, the maximal quantum yield of PSII (F F ), and antioxidant activities. With an increasing Fe concentration in the substrate, the CAT and APX antioxidant levels decreased, which led to an increase in HO accumulation in the plant tissues. Moreover, increased POD activity was proportionate to HO accumulation, suggesting the low-Fe independent nature of POD. Diurnally, HO concentration varies following the PAR variation. However, the CAT and APX antioxidant activities were delayed, which increased the HO concentration level in the afternoon compared with the level in morning for the same PAR intensities. Similar trends were also obtained for the natural river samples where relatively low light intensity was preferable for growth. Together with our previous findings on macrophyte stress responses, these results indicate that HO concentration is a good indicator of environmental stressors and could be used instead of long-term growth monitoring in macrophyte management.
在植被管理中，了解沉水植物的状况通常基于长期生长监测。活性氧（ROS）在环境胁迫下会在细胞器中积累，很可能是植物状况的指标。然而，这取决于暴露于环境胁迫的时间，因为自然界中的环境条件总是在变化。过氧化氢（HO）是细胞器中最常见的ROS。通过实验室实验和天然河流观测，研究了沉水大型植物对高光和铁（Fe）胁迫的响应。将植物置于光合有效辐射（PAR）强度为30 - 200 μmol m⁻² s⁻¹和培养基中铁浓度为0 - 10 mg L⁻¹的组合条件下培养。我们测量了HO、光合色素浓度、叶绿素a（Chl-a）、叶绿素b（Chl-b）、类胡萝卜素（CAR）、叶片组织中吲哚 - 3 - 乙酸（IAA）浓度、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）、过氧化物酶（POD）的抗氧化活性、PSII的最大量子产率（Fv/Fm）以及枝条生长速率（SGR）。HO浓度随培养基中铁浓度的增加而逐渐升高，但在极低浓度和PAR强度增加时除外。然而，在极高的PAR或Fe浓度下，叶绿素含量首先显著下降，随后HO浓度下降，接着是SGR、PSII的最大量子产率（Fv/Fm）和抗氧化活性下降。随着底物中铁浓度的增加，CAT和APX的抗氧化水平降低，这导致植物组织中HO积累增加。此外，POD活性的增加与HO积累成正比，表明POD具有低铁非依赖性。在白天，HO浓度随PAR变化而变化。然而，CAT和APX的抗氧化活性出现延迟，这使得在相同PAR强度下，下午的HO浓度水平比上午高。对于天然河流样本也获得了类似趋势，相对较低的光照强度更有利于其生长。与我们之前关于大型植物胁迫响应的研究结果一起，这些结果表明HO浓度是环境胁迫的良好指标，可用于大型植物管理中替代长期生长监测。
