Microplastics and nanoplastics are emerging pollutants of global importance. They are small enough to be ingested by a wide range of organisms and at nano-scale, they may cross some biological ...barriers. However, our understanding of their ecological impact on the terrestrial environment is limited. Plastic particle loading in agroecosystems could be high due to inputs of some recycled organic waste and plastic film mulching, so it is vital that we develop a greater understanding of any potentially harmful or adverse impacts of these pollutants to agroecosystems. In this article, we discuss the sources of plastic particles in agroecosystems, the mechanisms, constraints and dynamic behaviour of plastic during aging on land, and explore the responses of soil organisms and plants at different levels of biological organisation to plastic particles of micro and nano-scale. Based on limited evidence at this point and understanding that the lack of evidence of ecological impact from microplastic and nanoplastic in agroecosystems does not equate to the evidence of absence, we propose considerations for addressing the gaps in knowledge so that we can adequately safeguard world food supply.
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•We estimate maximum loadings in agroecosystem using existing regulations.•Lifetime loading of 2.8–63t·ha−1 of microplastics from biosolids use alone.•Biotic response is mediated by the organism, soil and plastic properties.•We deduce ecosystem impact by linking organismal response to ecological role.•Estimated loadings can be used to set up ecotoxicology experiments.
Plant biostimulants (PBs) attract interest in modern agriculture as a tool to enhance crop performance, resilience to environmental stress, and nutrient use efficiency. PBs encompass diverse organic ...and inorganic substances (humic acids and protein hydrolysates) as well as prokaryotes (e.g., plant growth promoting bacteria) and eukaryotes such as mycorrhiza and macroalgae (seaweed). Microalgae, which comprise eukaryotic and prokaryotic cyanobacteria (blue-green algae), are attracting growing interest from scientists, extension specialists, private industry and plant growers because of their versatile nature: simple unicellular structure, high photosynthetic efficiency, ability for heterotrophic growth, adaptability to domestic and industrial wastewater, amenability to metabolic engineering, and possibility to yield valuable co-products. On the other hand, large-scale biomass production and harvesting still represent a bottleneck for some applications. Although it is long known that microalgae produce several complex macromolecules that are active on higher plants, their targeted applications in crop science is still in its infancy. This paper presents an overview of the main extraction methods from microalgae, their bioactive compounds, and application methods in agriculture. Mechanisms of biostimulation that influence plant performance, physiology, resilience to abiotic stress as well as the plant microbiome are also outlined. Considering current state-of-the-art, perspectives for future research on microalgae-based biostimulants are discussed, ranging from the development of crop-tailored, highly effective products to their application for increasing sustainability in agriculture.
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•Resting operation stimulates wetland plants root redundancy.•The absorption of pollutants by plants was enhanced under the resting operation.•Resting operation enhanced microbial ...nitrogen fixation and assimilation.•Excessively long resting period (>5 d) led to limited denitrification function.•Resting operation changed root traits thus regulated rhizosphere microorganisms.
The stable operation of subsurface flow (SSF) constructed wetlands (CWs) depends on the adopted maintenance and management strategies. To determine a suitable resting period for SSF CWs, this study investigated and compared the impacts of three resting periods on plant physiological metabolism, wetland purification effectiveness, and microbial responses. The results revealed that resting operations induced morphological adaptations in wetland plants, significantly enhanced the root-shoot ratio and specific root length. A 2-d resting period enhanced oxygen secretion from plant roots, which was beneficial for SSF CW reoxygenation, leading to significant increases in the average removal rates of chemical oxygen demand and total phosphorus. After the resting operation, the inorganic phosphorus solubilization and transporters function of rhizosphere microorganisms were enhanced, resulting in efficient phosphorus removal. The functional genes related to nitrification, nitrogen fixation, and assimilation were increased, and a 2–5 d resting period facilitated the aerobic nitrification in SSF CWs. Inversely, an excessively long resting (>5 d) significantly inhibits plant and microbial activity, resulting in a deteriorated pollutant removal performance. Plants regulate rhizosphere microorganisms by adjusting root traits, which are the key factors and important reference indicators guiding the formulation of the operation and maintenance strategies for SSF CWs during resting periods.
Plants exposed to a variety of abiotic and biotic stressors including environmental pollution and global warming pose significant threats to biodiversity and ecosystem services. Despite substantial ...literature documenting how plants adapt to distinct stressors, there still is a lack of knowledge regarding responses to multiple stressors and how these affects growth and development. Exposure of plants to concurrent biotic and abiotic stressors such as cadmium and drought, leads to pronounced inhibition in above ground biomass, imbalance in oxidative homeostasis, nutrient assimilation and stunted root growth, elucidating the synergistic interactions of multiple stressors culminating in adverse physiological outcomes. Impact of elevated heavy metal and water deficit exposure extends beyond growth and development, influencing the biodiversity of the microenvironment including the rhizosphere nutrient profile and microbiome. These findings have significant implications for plant-stress interactions and ecosystem functioning that prompt immediate action in order to eliminate effect of pollution and address global environmental issues to promote sustainable tolerance for multiple stress combinations in plants. Here, we review plant tolerance against stress combinations, highlighting the need for interdisciplinary approaches and advanced technologies, such as omics and molecular tools, to achieve a comprehensive understanding of underlying stress tolerance mechanisms. To accelerate progress towards developing stress-tolerance in plants against multiple environmental stressors, future research in plant stress tolerance should adopt a collaborative approach, involving researchers from multiple disciplines with diverse expertise and resources.
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•Multiple environmental stressors interact to disrupt plant homeostasis.•Plant chooses single or multiple signalling pathways during exposure to stress combination.•Physio-biochemical and molecular mechanisms work together in plant against environmental hazards.•The plant-stress combination interactions disturb the ecosystem functioning and balance.•Future research should accelerate progress to develop stress-tolerance in plant species.
Understanding and predicting plant response to disturbance is of paramount importance in our changing world. Resprouting ability is often considered a simple qualitative trait and used in many ...ecological studies. Our aim is to show some of the complexities of resprouting while highlighting cautions that need be taken in using resprouting ability to predict vegetation responses across disturbance types and biomes. There are marked differences in resprouting depending on the disturbance type, and fire is often the most severe disturbance because it includes both defoliation and lethal temperatures. In the Mediterranean biome, there are differences in functional strategies to cope with water deficit between resprouters (dehydration avoiders) and nonresprouters (dehydration tolerators); however, there is little research to unambiguously extrapolate these results to other biomes. Furthermore, predictions of vegetation responses to changes in disturbance regimes require consideration not only of resprouting, but also other relevant traits (e.g. seeding, bark thickness) and the different correlations among traits observed in different biomes; models lacking these details would behave poorly at the global scale. Overall, the lessons learned from a given disturbance regime and biome (e.g. crown‐fire Mediterranean ecosystems) can guide research in other ecosystems but should not be extrapolated at the global scale.
Rising atmospheric CO
concentration is a key driver of enhanced global greening, thought to account for up to 70% of increased global vegetation in recent decades. CO
fertilization effects have ...further profound implications for ecosystems, food security and biosphere-atmosphere feedbacks. However, it is also possible that current trends will not continue, due to ecosystem level constraints and as plants acclimate to future CO
concentrations. Future predictions of plant response to rising CO
are often validated using single-generation short-term FACE (Free Air CO
Enrichment) experiments but whether this accurately represents vegetation response over decades is unclear. The role of transgenerational plasticity and adaptation in the multigenerational response has yet to be elucidated. Here, we propose that naturally occurring high CO
springs provide a proxy to quantify the multigenerational and long-term impacts of rising CO
in herbaceous and woody species respectively, such that plasticity, transgenerational effects and genetic adaptation can be quantified together in these systems. In this first meta-analysis of responses to elevated CO
at natural CO
springs, we show that the magnitude and direction of change in eight of nine functional plant traits are consistent between spring and FACE experiments. We found increased photosynthesis (49.8% in spring experiments, comparable to 32.1% in FACE experiments) and leaf starch (58.6% spring, 84.3% FACE), decreased stomatal conductance (g
, 27.2% spring, 21.1% FACE), leaf nitrogen content (6.3% spring, 13.3% FACE) and Specific Leaf Area (SLA, 9.7% spring, 6.0% FACE). These findings not only validate the use of these sites for studying multigenerational plant response to elevated CO
, but additionally suggest that long-term positive photosynthetic response to rising CO
are likely to continue as predicted by single-generation exposure FACE experiments.
Plants are exposed to a variety of abiotic stresses in nature and exhibit unique and complex responses to these stresses depending on their degree of plasticity involving many morphological, ...cellular, anatomical, and physiological changes. Phytohormones are known to play vital roles in the ability of plants to acclimatize to varying environments, by mediating growth, development, source/sink transitions and nutrient allocation. These signal molecules are produced within the plant, and also referred as plant growth regulators. Although plant response to salinity depends on several factors; nevertheless, phytohormones are thought to be the most important endogenous substances that are critical in modulating physiological responses that eventually lead to adaptation to salinity. Response usually involves fluctuations in the levels of several phytohormones, which relates with changes in expression of genes involved in their biosynthesis and the responses they regulate. Present review described the potential role of different phytohormones and their balances against salinity stress and summarized the research progress regarding plant responses towards salinity at physiological and molecular levels. We emphasized the role of abscisic acid, indole acetic acid, cytokinins, gibberellic acid, salicylic acid, brassinosteroids, jasmonates, ethylene and triazoles in mediating plant responses and discussed their crosstalk at various baseline pathways transduced by these phytohormones under salinity. Current progress is exemplified by the identification and validation of several significant genes that enhanced crops tolerance to salinity, while missing links on different aspects of phytohormone related salinity tolerance are pointed out. Deciphering mechanisms by which plant perceives salinity and trigger the signal transduction cascades via phytohormones is vital to devise salinity related breeding and transgenic approaches.
•The concentrations and mobility of metals/metalloids in red mud were assessed.•The response of soil extractable metals/metalloids to red mud addition was compared.•Key controls on metal/metalloid ...fixation due to red mud application were identified.•Effects of red mud amendment of contaminated soil on plant growth were described.•Bacterial activity was intensified in red mud-amended contaminated soil.
This review focuses on the applicability of red mud as an amendment for metal/metalloid-contaminated soil. The varying properties of red muds from different sources are presented as they influence the potentially toxic element (PTE) concentration in amended soil. Experiments conducted worldwide from the laboratory to the field scale are screened and the influencing parameters and processes in soils are highlighted. Overall red mud amendment is likely to contribute to lowering the PTE availability in contaminated soil. This is attributed to the high pH, Fe and Al oxide/oxyhydroxide content of red mud, especially hematite, boehmite, gibbsite and cancrinite phases involved in immobilising metals/metalloids. In most cases red mud amendment resulted in a lowering of metal concentrations in plants. Bacterial activity was intensified in red mud-amended contaminated soil, suggesting the toxicity from PTEs was reduced by red mud, as well as indirect effects due to changes in soil properties. Besides positive effects of red mud amendment, negative effects may also appear (e.g. increased mobility of As, Cu) which require site-specific risk assessments. Red mud remediation of metal/metalloid contaminated sites has the potential benefit of reducing red mud storage and associated problems.
•Red and far-red control development, nutrition, tolerance to drought and pests.•Mechanistic bases are progressively being unveiled.•Plant responses depend on species and growing conditions.•Handling ...light quality can improve the economic value of horticultural production.
Light drives plant growth and development, so its control is increasingly used as an environment-friendly tool to manage horticultural crops. However, this implies a comprehensive view of the main physiological processes under light control, and bridging knowledge gaps. This review presents the state of the art in (i) perception of red (R) and far-red (FR) wavelengths and of the R:FR ratio by plants, (ii) phenotypic plant responses, and (iii) the molecular mechanisms related to these responses. Changes in red or far red radiation and R:FR ratios are perceived by phytochromes. Phytochrome-mediated regulation is complex and specific to each physiological process. Our review presents the effects of red and far-red lights on germination, aerial architectural development, flowering, photosynthesis and plant nutrition. It also addresses how red and far-red radiations interact with tolerance to drought, pathogens and herbivores. Current knowledge about the mechanisms whereby red, far-red and R:FR regulate these different processes is presented. The specific actors of light signal transduction are better known for germination or flowering than for other processes such as internode elongation or bud outgrowth. The phenotypic response to red, far-red and R:FR can vary among species, but also with growing conditions. The mechanisms underlying these differences in plant responses still need to be unveiled. Current knowledge about plants’ response to light is being applied in horticulture to improve crop yield and quality. To that purpose, it is now possible to manipulate light quality thanks to recent technological evolutions such as the development of photo-selective films and light-emitting diodes.
Dramatic accumulation of proline is a common physiological response in plants exposed to various abiotic stresses. Accumulation of proline could be due to de novo synthesis, decreased degradation, ...lower utilization, or hydrolysis of proteins. Extensive intercellular proline transport occurs between the cytosol, chloroplasts, and mitochondria due to its compartmentalized metabolism. Although all functions of proline in stress tolerance are still a matter of debate, it is suggested that proline contributes to stabilization of sub-cellular structures, scavenging free radicals, and buffering cellular redox potential. It also chelates heavy metals, modulates cellular functions, and even triggers gene expression. Apparently, proline acts as stress-related signal exhibiting cross tolerance to a range of different stresses. Besides these significant roles, its metabolism is found to be coupled to several key pathways such as pentose phosphate, tricarboxylic acid, or urea cycles and contributes to, i.e., purine synthesis and the phenylpropanoid pathway. Although the molecular basis of regulation of proline metabolism is still largely obscure, the genetic engineering of proline content could lead to new opportunities to achieve plant stress tolerance.
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