Microwave exposure added characteristics to the wounding-induced variation potential of Aloe arborescens leaves

The influence of radiofrequency electromagnetic radiation on the wounding-induced electric potentials (EPs) in Aloe arborescens plants was investigated. Burn wounding-induced electrical potentials of mature A. arborescens plants were observed under the exposure of 2.45 ​GHz, 3.5 ​GHz and 5.5 ​GHz microwaves at incident power density 1.5 ​± ​0.2 ​W ​m−2. Aloe leaves were subjected to flame wounding at the leaf tips and propagation EPs were recorded by inserting a glass Ag/AgCl microelectrode into the leaf pulp. The propagation of electrical potential and a standard deviation of the fluctuations in electrical potential (SDEF) were investigated. The flame wounding generated propagating characteristic electric potential, and the exposure of microwaves added extra characteristics to the signals by reversing the electrical potential temporally for a shorter duration. The characteristics appeared in the repolarization phase of the signal under 2.45 ​GHz and 3.5 ​GHz exposure; for the 5.5 ​GHz exposure, 3 out of 6 characteristics appeared during the depolarization phase. Averaged polarization rates of the characteristics were increased with the increased microwave frequency. Added characteristics to the electric potential may have resulted from a secondary signal triggered due to microwave exposure, which should be further studied. The repolarization and depolarization rates of the wound signals were not different between control and microwave exposures. SDEFs were also not affected by microwave exposure

Recoverability of <i>Microcystis aeruginosa</i> and <i>Pseudanabaena foetida</i> Exposed to a Year-Long Dark Treatment

Cyanobacteria are a significant primary producer and pioneer species that play a vital role in ecological reconstruction, especially in aquatic environments. Cyanobacteria have excellent recovery capacity from significant stress exposure and are thus suggested as bioreserves, even for space colonization programs. Few studies have been conducted on the recovery capacity after experiencing stress. Long-duration darkness or insufficient light is stressful for photosynthetic species, including cyanobacteria, and can cause chlorosis. Cyanobacterial recovery after extensive exposure to darkness has not yet been studied. In this experiment, Microcystis aeruginosa and Pseudanabaena foetida were subjected to a year-long darkness treatment, and the change in recovery capacity was measured in monthly samples. Cyanobacterial growth, chlorophyll-a concentration, oxidative stress, and photosynthetic capacity were evaluated. It was found that the rapid recovery capacity of the two species remained even after one year of darkness treatment. However, the H2O2 content of recovered samples of both M. aeruginosa and P. foetida experienced significant changes at six–seven months, although the photosynthetic capacity of both cyanobacteria species was maintained within the healthy range. The chlorophyll-a and carotenoid content of the recovered samples also changed with increasing darkness. The results showed that long-term dark treatment had time-dependent effects but different effects on M. aeruginosa and P. foetida. However, both cyanobacteria species can recover rapidly after one year of dark treatment

Inhibitory Effect of Aqueous Extracts from <i>Egeria densa</i> Planch. on Cyanobacteria <i>Microcystis aeruginosa</i> (Kützing) Lemmermann Growth

This study aimed to investigate the allelopathic effect of live Egeria densa Planch. and its aqueous extracts in inhibiting the cyanobacterium Microcystis aeruginosa (Kützing) Lemmermann through a possible growth inhibition pathway. Under coexistence, the presence of live E. densa reduced the growth of M. aeruginosa by 48% compared to when M. aeruginosa was alone. Consequently, we prepared two separate aqueous extracts with distilled water: one from E. densa plants collected from monocultures, and the other from E. densa plants collected from co-cultivation with M. aeruginosa. At a concentration of 0.5 g/L, both extracts successfully suppressed the growth of M. aeruginosa throughout the 5-day exposure period. The extracts obtained from E. densa plants grown in a combined culture with M. aeruginosa showed significant growth-inhibiting capabilities compared to the extracts obtained from E. densa monoculture (p E. densa was induced during co-existence with cyanobacteria. However, the higher concentrations (2 and 4 g/L) of both extracts did not effectively exhibit a successful inhibitive ability, possibly due to the presence of high nutrient concentrations, specifically PO43−, which may be potentially suppressing the activity of allelochemicals. Further studies are recommended in identifying the specific allelochemicals and exploring their practical implementation in the field

Application of Hydrogen Peroxide as an Environmental Stress Indicator for Vegetation Management

Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species (ROS) has long been used as an indicator of environmental stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide (H2O2) is relatively stable, and can be conveniently and accurately quantified. Thus, the quantification of plant H2O2 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H2O2 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and field conditions (Lake Shinji, Saba River, Eno River, and Hii River in Japan) for H2O2 formation under various stress conditions. The results suggest that H2O2 can be conveniently applied as a stress indicator in environmental management. Keywords: Macrophytes, Riparian zone, Environmental gradient, Stress indicator, Reactive oxygen species, Hydrogen peroxid

Effects of short-term exposure to different salinity levels on

Sea-level rise caused by global warming is leading to increased freshwater salinization, which causes significant stress on aquatic ecosystems and species, including macrophytes. To form a better understanding of the responses of macrophytes to salinity stress, we assessed biochemical, pigmentation and growth responses of Myriophyllum spicatum L. and Ceratophyllum demersum L. exposed to different salinity levels (0, 1.5, 2.5, 5.0, and 10 ppt). For both species, elongation rates decreased, and levels of photosynthetic pigments (chlorophyll a and chlorophyll b) increased at higher salinities (5 ppt and 10 ppt). Anthocyanin and H2O2 concentrations increased in M. spicatum but decreased in C. demersum with the increase in salinity. The activities of antioxidant enzymes (guaiacol peroxidase, catalase, and ascorbate peroxidase) were different between two species and fluctuated along the salinity gradient. M. spicatum and C. demersum exhibit species-specific salinity sensitivities, reaching different physiological statuses at each salinity level. Elongation rates were significantly correlated with several biochemical parameters in a species-specific manner. These correlations can be used in evaluating the expected responses of these two species to salinity changes. The species-specific responses of most parameters measured in the present study suggests the inapplicability of common biochemical responses across species.M. spicatum and C. demersum exposed to different salinity levels in a laboratory study. Two species exhibited species-specific salinity sensitivities reaching different physiological statuses at each salinity level. Elongation rates were correlated with several biochemical parameters. These correlations can be used in evaluating the expected responses of two species to salinity

A Review of Emerging Scientific Discussions on Green Infrastructure (GI)-Prospects towards Effective Use of Urban Flood Plains

The goal of the present review is to collect data on trending scientific discussions on applying green infrastructure (GI) approaches to the effective use of urban floodplains and conceptualize potential future directions. A systematic literature review methodology was employed for this review. We reviewed 120 scholarly articles published between 2011 and 2022 under a predefined protocol. In this review, we discuss the trending dialogues on GI approaches and their applications. The research gap in applying GI approaches for macro-level urban-flood-plain management is addressed by (a) speculative arguments drawn from reviewed GI case studies, (b) an analysis of the trends’ strengths, weaknesses, opportunities, and threats (SWOT), and (c) presenting the concurrent ‘green–gray’ debate on neutral ground. Evidently, GI has its strengths and opportunities, as well as weaknesses and threats. The approaches to GI can be customized according to the application purpose, the regional or locational context, and the intended capacity. Following the analysis of emerging GI discussions, we position the current GI dialogues into four categories: (i) the green–gray continuum; (ii) GI for sustainable and resilient cities; (iii) GI as a resolution for urban issues; and (iv) the green–gray debate. In this classification, we strongly argue that placing GI in a more certain and instrumental position can be optimally achieved in the ‘green–gray continuum’ concept with a win–win scenario. Therefore, scientifically investigating the ‘green–gray continuum’ possibilities in a futuristic approach is strongly recommended