What are the growth kinetics and biochemical compositions of microalgae isolated from diverse aquatic ecosystems in Morocco, France, and Tunisia?

Thirty-six microalgae belonging to five taxonomic groups (Cyanobacteria, Chlorophyceae, Diatomophyceae, Euglenophyceae, and Eustigmatophyceae) were identified from six freshwater ecosystems in Morocco, two treatment stations in Etueffont landfill in France and three hot spring waters in Tunisia. Investigations on species growth kinetics and growth rates showed that the cyanobacterium Leptolyngbya gelatinosa exhibited both the highest biomass and growth rate with 4 g DW L-1 and 0.282 day-1, respectively. A significant protein production (more than 40% DW) was observed across the studied species. Cyanobacteria and chlorophytes stood out for their increased protein production with a maximum (66.63 ± 3.84% DW) attained by the cyanobacterium Leptolyngbya sp. Chlorophytes produced substantial amounts of carbohydrates (more than 20% DW). Euglenophytes including Phacus orbicularis and Euglena ehrenbergii along with the chlorophyte Graesiella sp. accumulated significant amounts of lipids (up to 31.12% DW).

Ayurveda Rasayana as antivirals and immunomodulators: potential applications in COVID-19.

Coronavirus disease (COVID-19) has been declared as a pandemic by the World Health Organization with rapid spread across 216 countries. COVID-19 pandemic has left its imprints on various health systems globally and caused immense social and economic disruptions. The scientific community across the globe is in a quest for digging the effective treatment for COVID-19 and exploring potential leads from traditional systems of healthcare across the world too. Ayurveda (Indian traditional system of medicine) has a comprehensive aspect of immunity through Rasayana which is a rejuvenation therapy. Here we attempt to generate the potential leads based on the classical text from Ayurveda in general and Rasayana in particular to develop effective antiviral and/or immunomodulator for potential or adjunct therapy in SARS-CoV-2. The Rasayana acts not only by resisting body to restrain or withstand the strength, severity or progression of a disease but also by promoting power of the body to prevent the manifestation of a disease. These Rasayana herbs are common in practice as immunomodulator, antiviral and protectives. The studies on Rasayana can provide an insight into the future course of research for the plausible development of effective management of COVID-19 by the utilization and development of various traditional systems of healthcare. Keeping in view the current pandemic situation, there is an urgent need of developing potential medicines. This study proposes certain prominent medicinal plants which may be further studied for drug development process and also in clinical setup under repurposing of these herbs.

Growth, pigment changes, and photosystem II activity in the aquatic macrophyte Lemna minor exposed to bisphenol A.

As a result of its high production, bisphenol A (BPA) has become ubiquitous in aquatic and terrestrial habitats. In this study, we investigated the toxicity of BPA at 10 mg L-1 on Lemna minor after 7 days of exposure under controlled conditions according to ISO 20079. BPA statistically reduced the total frond number and frond area, while frond number per colony was significantly elevated in BPA-treated group. However, no change was recorded in root number, while root length was significantly reduced by BPA. BPA also decreased the content of Chl a, Chl b, Chl a + b, and carotenoid by 36%, 44%, 38%, and 32%, respectively, versus the control leading to a decrease in the quantum yield of photosystem II. In addition, non-photochemical quenching (NPQ) values were 2.4- and 4.5-fold higher in light than in dark conditions for control and BPA-treated plants, respectively. Thus, there is a significant activation (61.8%; p<0.01) of PSII photoprotection mechanism (NPQ) in BPA-treated plants compared to control but without removing the negative effect of BPA on PSII. The total amount of soluble sugars was reduced by 40% compared to control, and starch accumulation was mainly observed in fronds exposed to BPA. Even if the response patterns of Lemna minor based on fresh and dry weight measurements were less sensitive in our experiment conditions, further studies should be addressed since BPA represents a threat to the dynamic equilibrium governing aquatic ecosystems.

Expatiating the impact of anthropogenic aspects and climatic factors on long-term soil monitoring and management.

This article is an extensive collection of scientific literature related to the impact of fertilizers on soil microbial and enzymatic activity. Due to the significance of technology in quantitative and qualitative evaluation of agricultural production, this is a basic problem for the present and future of mankind, where the scientific data being of utmost importance related to the topic. The comparison, including pedo-enzymological evaluation of minerals along with organic fertilization, highlights significant differences between mineral and organic fertilizers, confirming the superiority of complex mineral-organic fertilization. Enzymatic indicators that describe and define the soil quality resulted from enzymatic activities value and provide valuable information regarding the soil fertility status. Moreover, soil enzyme responds to soil management as well as to environmental pollutants. Changes of environmental conditions and pollutants like heavy metals and other toxic substances result in a shift in the biological activity of the soil. These changes can destabilize the soil system and cause a decrease in the nutrient pools. To ensure the improvement of fertilization techniques, the properties of nanoparticles are exploited that can efficiently release nutrients to plant cells. Numerous researches were performed in order to follow the long-term effects of incorporating nanofertilizers into the soil, obtaining an exhaustive overview of this new technology over the development of sustainable agriculture.

Influence of hydro- and osmo-priming on sunflower seeds to break dormancy and improve crop performance under water stress.

This study explored the effects of two hydro- and osmo-priming durations (8 and 16 h) on growth and yield components of sunflowers (Helianthus annuus L.) under water stress. The pot experiment, performed under a rain shelter, consisted of 9 treatments replicated five times: unprimed seeds as control (C), hydro-primed seeds (T0), osmo-primed seeds in 10, 20, and 30% PEG-6000 (T1, T2, and T3, respectively). Severe water stress was applied for 12 days to all treatments at the beginning of the flowering stage. Statistical analysis revealed a very highly significant positive effect (p < 0.01) by all treatments on sunflower seed germination compared with the control. Moreover, primed seeds improved significantly for all growth parameters and yield components, but no significant differences were observed according to either priming technique or duration. The highest value of germination capacity, for fresh and dry biomasses, was obtained with PEG-primed seeds at 10% for 16 h. The grain number per anthodium and grain yield per plant from primed seeds were higher than those in the control (1.9- to 2.5-fold and 2.8- to 3.3-fold respectively). Under conditions of water stress, the proline content in primed plants was significantly higher than that in unprimed ones, with the exception of T3 treatment primed for 8 h. Soluble sugars and chlorophyll contents increased significantly with all applied treatments compared with the control. The study showed that the applied priming treatments improved germination characteristics in particular and increased growth and yield components for sunflowers under drought stress conditions.

Performance assessment of Etueffont (France) lagooning treatment system: Report from a 16-year survey.

This study examined the lagooning treatment system of the Etueffont landfill (France) over a period of 16 years. Outflow concentrations in total suspended solids, biological oxygen demand (BOD5) and trace metal elements largely met outflow standards and were on average of 5, 8 and 6 times lower than those observed at inflow, respectively. In 2000, however, high levels of BOD5 were observed in both the influent and effluent, exceeding the authorized outflow limits. At that time the lagooning ponds were subjected temporarily to organic pollution, coinciding with the arrival of the first leachates from a new cell. Though the chemical oxygen demand (COD) and total organic carbon in the influent exceeded authorized limits, overall values conformed to official standards with outflow exhibiting mean concentrations four times lower than those observed at inflow. The first period took place just after the arrival from the new cell of young leachates containing a very high level of COD (>10,000 mg L-1), causing an organic overload that led to a temporary dysfunctioning of the treatment installation lasting approximately two years. Additionally, the COD in the leachates fell below the strictest limits (125 mg L-1) at the end of monitoring (2005-2009). The initial nitrogen load brought in by the influent decreased progressively over time, evidence of continuous degradation. At the end of monitoring, regardless of the arriving inflow load, the discharge presented stable concentrations of approximately 30 mg L-1, appearing to indicate that the limits for nitrogen elimination. Total phosphorus elimination was optimal as the concentrations at outflow were minimal throughout most of monitoring, even though the phosphorus load at inflow was from two to thirty-five times greater. Thus, the findings show that landfill leachates in the methanogenic phase can be treated efficiently by lagooning without risk to the surrounding environment.

Proposed changes for post-closure monitoring of Etueffont landfill (France) from a 9-year survey.

Environmental monitoring must be continued following landfill closure for at least 30 years according French Waste Disposal Law. The goal of this investigation was to verify whether measures taken with respect to surveillance and control of leachates, surface and ground water originated from closed landfill site in France are sufficient to ensure reliable long-term environmental monitoring. This study is based on the first nine years of the Etueffont landfill's post-closure phase, from 2002 to 2010. In 2007, the site's piezometric network has 17 piezometers. Four supplementary sampling points were also added in up- and downstream of Gros Près and Mont Bonnet Brooks. No raw leachate was discharged directly into the natural environment. Piezometric monitoring has been undertaken monthly. Groundwater and effluent discharges were sampled twice per year, in January and July, while surface water was sampled three times annually. By taking into account all of the monitoring parameters imposed by the Decree of 9 September 1997 amended, the recorded values were all lower than the strictest standards (non-applicable) at the end of monitoring (2005-2010). The discharge is therefore of a much higher quality than required. Several parameters were undetected in the surface waters since their levels were below analytical detection limits. The average purification efficiency observed between upstream (the source) and downstream (MB Brook), observed to be between 72 and 91%, shows just how well the receiving environment can purify contaminated waters by natural attenuation. The groundwater present throughout the monitoring period to be at concentrations below the standards for the following parameters: Total phosphorus, Total nitrogen, Escherichia coli (E. coli), As, Zn, Cd and Cr. In contrast, some excesses are occasionally observed for the organic parameters (TOC, COD and BOD). Thus, this study shows the flaws inherent in the environmental monitoring program imposed by the Decree of 9 September 1997. Consequently, the program has indeed been adapted to the monitoring of effluent discharges and surface water quality since the decree does set quality standards.

Influence of different sludge compositions on understorey vegetation in an amended Pinus pinatser forest plantation.

The present study reports on the influence of sludge application on understory abundance and species richness in an eight year-old maritime pine forest. Four types of sludge (liquid, dewatered, limed and composted sludge) were applied at a rate equivalent to 3 tons dry weight per ha-1 per year-1. Understorey vegetation was monitored before treatment and for three successive years following initial sludge application. Species richness, the biodiversity index and naturally occurring plant community cover in maritime pine forests were measured. Results showed a significant increase in species richness two years following initial sludge application. In fact, compared to the unamended plot, eighteen additional species (Aira caryophyllea, Cerastium glomeratum, Conyza canadensis, Danthonia decumbens, Geranium robertianum, Gnaphalium sylvaticum, Hypericum humifusum, Hypericum perforatum ssp. perforatum, Jasione montana, Lonicera periclymenum ssp. periclymenum, Ornithopus compressus, Phytolacca americana, Rhamnus frangula, Teesdalia nudicaulis, Veronica arvensis, Vicia sativa angustifolia and Vulpia myuros) appeared after sludge application. Most of these species were observed with the solid limed or composted sludge treatments. The new species then declined the following year, highlighting the temporary effect of sludge treatment on species diversity. However, the cover by these eighteen new species was low and did not exceed 1%, except for Hypericum perforatum and Jasione montana for the limed sludge treatment and Vulpia myuros for the liquid sludge treatment. Additionally, sludge significantly reduces bare soil percentage, which ranged from 5 to 18% compared to the control (38%). According to sludge type, treatment also led to a significant change in species dominance of the understorey plant communities. Indeed, the cover of Molinia caerulea decreased in spite of an increase in Agrostis capillaris and/or Holcus lanatus following application of solid limed, liquid or composted sludge.

Effects of sodium chloride salinity on ecophysiological and biochemical parameters of oak seedlings (Quercus robur L.) from use of de-icing salts for winter road maintenance.

Salt is widely used to melt snow on roads especially in mountain regions. Whether as rock salt or aerosols, spread or sprayed over road surfaces, salt may result in increased salt concentrations in soils, which, in turn, affect natural vegetation, especially tree seedlings already subjected to various other types of abiotic stress. The authors investigated the effects of salt treatment-related stress on seedling growth and certain biochemical parameters in Quercus robur to determine ion concentrations in root tips. Seedlings growing in a quartz sand/vermiculite mixture were subjected to NaCl concentrations of 0, 50, or 100 mM for 5 weeks. The results showed that high NaCl concentrations caused a marked reduction in total leaf biomass 55 and 75% for 50 and 100 mM treatments, respectively, in dry weight of stems (84%) and roots (175%) for 100 mM treatment and modified root architecture, whereas no changes appeared in leaf number. A non-significant decrease in relative water content, with changes in ion balance was recorded. Comparison of stressed to control plants show an increase in sodium (3.5-8-fold), potassium (0.6-fold), and chloride (9.5-14-fold) concentrations in the root tips while the K+/Na+ ratio decreased. In taproots, no significant biochemical differences were observed between the salt-treated and the control plants for acid invertase activity, reducing sugars, sucrose, or soluble protein contents. The significance of ion and sugar accumulations in relation to osmotic adjustment and the ability of oak seedlings to cope with salt stress are discussed.

Potential vulnerability of oak forests to climate change-induced flooding: effects of mild oxygen deficiency on Quercus robur and Quercus petraea seedling physiology.

Flooding is characterized by saturation of soil pores with water, leading to hypoxic conditions which affect plant root development and metabolism. We investigated the oxygen deficiency tolerance observed in Quercus robur and Quercus petraea and seek to understand whether it can be explained by enhanced efficiency in oxygen use in the roots, as estimated through radial oxygen loss visualization in relation to growth measurements and root apex respiration. The study showed that root growth, under oxygen deficiency conditions, was significantly reduced only in Q. robur seedlings. Root respiration was maintained in Q. robur, whereas it was decreased in Q. petraea. Both species set up a barrier against radial oxygen loss, though measurement of apex oxygen leakage showed greater oxygen efficiency in Q. robur seedlings. This strategy might allow Q. robur to maintain its respiration and thus to survive longer under oxygen deficiency conditions by facilitating the seedling establishment in transient flooded soils.

Sewage sludge as a soil amendment in a Larix decidua plantation: Effects on tree growth and floristic diversity.

Sewage sludge application in forest plantations is an interesting complementary alternative practice to sewage sludge reutilization and recycling, with a significant and sustainable net effect in climate change mitigation. However, to optimize it a detailed knowledge of its effects on ecosystem components such as plants, soil, water and fauna is needed. We investigated the effects of sewage sludge application on soil, tree growth and floristic diversity in a ten-year-old plantation of European larch (Larix decidua Mill.). Our one-hectare study site, located at Mélisey, Haute-Saône, France (47°753' Lat., 6°580' Long.), was subdivided into six plots. Three plots, alternating with three control plots (no sewage sludge application), were amended in June 2008 with 0.4tDWha-1 obtained from a municipal urban wastewater treatment plant in Mélisey. Within each plot, one subplot was delimited and sludge was again manually applied at 3t of DWha-1 in July 2009 and March 2010 to the soil surface of the amended subplots without incorporation. The results showed no effect on radial and height growth of European larch amended with 0.4tDWha-1. While a significant temporary increase in pH, macro-element contents (N, P and Ca) and the trace metal (Cu and Zn) concentration in the soil was observed, it had no significant effect on needles and sporocarp contents. The number of species in the amended subplots with 3tDWha-1year-1 increased by 80% compared to the control. However, the relative species abundance present only in amended subplots remains <1, except for Hypericum humifusum.

Effects of repeated soil irrigation with liquid biological paper sludge on poplar Populus alba saplings: potential risks and benefits.

The authors explored the risks and benefits of repeated irrigation of Populus alba saplings with aqueous paper sludge (APS). Saplings were cultivated in pots of forest soil (3 L) in a greenhouse for 7 weeks and watered twice a week with differing concentrations of APS (0, 10, 20, 30, 50, 75, and 100 % v/v with deionized water). Plant growth and ecophysiological variables along with zinc and aluminum transfer were monitored. A stimulation of plant growth was observed with sludge treatments of 30 or 50 %, significantly correlated to APS input (r = 0.81). This may be explained by the easily available nitrogen as is shown with the positive correlation of CO2 assimilation and leaf nitrogen (r = 0.70). However, a significant reduction in plant growth was observed when treatments of 75 and 100 % of APS were administered, despite a high nutritional level (nitrogen and phosphorus). The study suggests that APS concentrations from 30 to 50 % may positively affect the growth of poplar saplings; however, the higher concentrations indicated a risk for plant growth and the environment.

Sensing and signalling during plant flooding.

Flooding is a major issue for plant survival in many regions of the world. Soil inundation induces multiple plant physiological dysfunctions, leading to a decline in plant growth and survival capacity. Some of the most important effects of flooding include a reduction in water and nutrient uptake and a decrease in metabolism. Prolonged soil flooding will also ultimately lead to anoxia conditions with profound effects on plant respiratory metabolism. However, it is still unclear which signals and which sensory mechanisms are responsible for triggering the plant response. In contrast, it is now established that flooding responses are typified by enhanced ethylene production, accompanied by a signalling cascade which includes a network of hormones and other common secondary signalling molecules. In recent years, there has been significant progress in the understanding of some of the signalling pathways involved during plant stress responses. Here, we present an overview of recent hypothesises on sensing and signalling during plant flooding.