Campomanesia xanthocarpa (Myrtaceae: Myrtoideae) seedlings reveal morpho-physiological plasticity under shade conditions

Plants exposed to different light intensities generate physiological, morphological, and anatomical changes conducting to plasticity. Thus, this characteristic establishes the ability of plants to present phenotypic adjustments by the same genotype under different environmental conditions. The objective of this study was to verify the morphophysiological alterations in Campomanesia xanthocarpa (Mart.) O. Berg (guabiroba) seedlings cultivated in different shading levels. The seedlings were grown for 21 months under full sun or 30%, 50%, and 80% under shading. Growth, photosynthetic pigments, gas exchange rate, chlorophyll fluorescence, and leaf anatomy were evaluated. In all the treatments subjected to shading, plasticity mechanisms involved structural and physiological changes such as an increase in leaf area and chlorophyll content (total and Chl a), reduction in leaf thickness, and increased gas exchange and quantum yield of photosystem II. The guabiroba seedlings can be cultivated in full sun or different shading environments; even under high shading intensity (80%), the plants showed vigor similar to those produced in a sunny environment. These results confirmed our hypothesis about guabiroba acclimation capacity to shading, noteworthy information for nurseries, orchards, agroforestry systems, or forest restoration in a wide range of light environments.

Phytoremediation: A green and low-cost technology to remediate herbicides in the environment

Pesticide dependence is one of the main disadvantages of agriculture. Despite the advances in biological control and integrated management of plant pests and diseases in recent years, herbicides are still essential for weed control and constitute the main class of pesticides worldwide. Herbicide residues in water, soil, air, and non-target organisms are among the biggest agricultural and environmental sustainability obstacles. Therefore, we suggest an environmentally viable alternative to reduce the harmful effects of herbicide residues, a technology called phytoremediation. Remediating plants were grouped into herbaceous, arboreal, and aquatic macrophytes. Phytoremediation can reduce the loss of at least 50% of all herbicide residues to the environment. Among the herbaceous species reported as phytoremediators of herbicides, the Fabaceae family was mentioned in more than 50% of reports. This family is also among the main species of trees reported. Regarding the most reported groups of herbicides, it is observed that most of them, regardless of the group of plants, are triazines. Processes such as extraction or accumulation are the best known and reported for most herbicides. The phytoremediation may be effective against chronic or unknown herbicide toxicity. This tool can be included in proposals for management plans and specific legislation in countries, guaranteeing public policies to maintain environmental quality.

Neuroprotective potential of Cannabis sativa-based oils in Caenorhabditis elegans

Substances from the Cannabis sativa species, especially cannabidiol (CBD) and Delta-9-tetrahydrocannabinol (Δ9-THC), have attracted medical attention in recent years. The actions of these two main cannabinoids modulate the cholinergic nervous system (CholNS) involving development, synaptic plasticity, and response to endogenous and environmental damage, as a characteristic of many neurodegenerative diseases. The dynamics of these diseases are mediated by specific neurotransmitters, such as the GABAergic nervous system (GNS) and the CholNS. The nematode Caenorhabditis elegans is an important experimental model, which has different neurotransmitter systems that coordinate its behavior and has a transgene strain that encodes the human β-amyloid 1–42 peptide in body wall muscle, one of the main proteins involved in Alzheimer´s disease. Therefore, the objective of this study was to evaluate the protective potential of terpenoids found in C. sativa in the GNS and CholNS of C. elegans. The effect of two C. sativa oils with variations in CBD and THC concentrations on acetylcholinesterase (AChE) activity, lipid peroxidation, and behavior of C. elegans was evaluated. C. sativa oils were efficient in increasing pharyngeal pumping rate and reducing defecation cycle, AChE activity, and ROS levels in N2 strains. In the muscle:Abeta1-42 strain, mainly when using CBD oil, worm movement, body bends, and pharyngeal pumping were increased, with a reduced AChE activity. Consequently, greater investments in scientific research are needed, in addition to breaking the taboo on the use of the C. sativa plant as an alternative for medicinal use, especially in neurodegenerative diseases, which have already shown positive initial results.

Redox status upon herbicides application in the control of Lolium multiflorum (2n and 4n) as weed

Lolium multiflorum Lam. is a winter weed of difficult control found as diploid (2n) and tetraploid plants (4n). Our study aimed to evaluate the responses of antioxidant enzymes and lipid peroxidation, in both diploid and tetraploid ryegrass varieties. Treatments consisted of control plants (without any herbicide application), and four herbicides with different mechanisms of action. Leaf material was collected 36 h after treatment imposition to determine the lipid peroxidation by ferrous oxidation-xylenol (FOX) content, and the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione-S-transferase (GST), and δ-aminolevulinic acid dehydratase (ALAD). Both ryegrass varieties showed oxidative stress mainly due to a downregulated decreased (>31%) in SOD activity and an increase (>32%) in lipid peroxidation (FOX), mainly in ryegrass genotypes exposed to haloxyfop, glyphosate, and iodosulfuron. On the other hand, clethodim-treated plants had an increase in SOD and APX activities, associated with a reduced ALAD activity in both 2n (32%) and 4n (11%) genotypes. In general, the 2n genotype was more affected than the 4n genotype.

Morphophysiological changes of Acca sellowiana (Myrtaceae: Myrtoideae) saplings under shade gradient

Understanding morphological and physiological changes under different light conditions in native fruit species in juveniles' stage is important, as it indicate the appropriate environment to achieve vigorous saplings. We aimed to verify growth and morphophysiological changes under shade gradient in feijoa (Acca sellowiana (O. Berg) Burret) to achieve good quality saplings adequate to improve cultivation in orchards. The saplings were grown for twenty-one-month under four shading treatments (0%, 30%, 50%, and 80%). Growth, photosynthetic pigments, gas exchanges, chlorophyll fluorescence, and leaf anatomy parameters were evaluated. Saplings under full sun and 30% shade had higher height and diameter growth and dry mass accumulation due to higher photosynthesis rate. As main acclimatization mechanisms in feijoa saplings under 80% shade were developed larger leaf area, reduced leaf blade thickness, and enhanced quantum yield of photosystem II. Even so, the net CO2 assimilation and the electron transport rate was lower and, consequently, there was a restriction on the growth and dry mass in saplings under deep shade. Therefore, to obtain higher quality feijoa saplings, we recommend that it be carried out in full sun or up to 30% shade, to maximize the sapling vigor in nurseries and, later, this light environment can also be used in orchards for favor growth and fruit production.

Interaction between pesticides applied alone or in mixtures in corn

The objective of this work was to evaluate the selectivity of herbicides applied alone or in tank mix, and also of combinations of different classes of pesticides (fungicides, herbicides and insecticides) on corn. An experiment was installed in the 2017/18 crop to assess herbicide selectivity, and repeated in 2018/19. The second experiment aimed to assess the selectivity of mixtures of different classes of pesticides, and was installed only in 2017/18. The experimental design adopted in the tests was randomized blocks, with four replicates. In each trial, a total of 16 treatments were evaluated, plus a control. At 7, 14 and 21 days after the application of treatments the phytotoxicity to corn was evaluated and the yield components and grain yield were determined. Herbicides caused low levels of injury to the corn plants, with small variations in yield components, and affected crop yield differently. The mixtures of pesticides promoted low phytotoxicity, affected yield components inconsistently and caused changes in corn yield. Although these herbicides and other pesticides are registered for use in corn crops, application alone or in tank mix of certain molecules can cause losses in grain yield.

Tank mixture of glyphosate and 2,4-D applied on RR® maize crop

Herbicide tank-mixing is often carried out by farmers aiming to control weeds in crops. Thus, it is important to evaluate the effects of these mixtures regarding the selectivity of crops. The aim of this work is to assess the selectivity of increasing doses of herbicides (glyphosate and 2,4-D), applied alone or as a mixture, on maize crop. Two experiments were carried out in randomized blocks, with four replications, during two crop years. The evaluated variables were: phytotoxicity, plant height, stem diameter, ear length, number of rows per ear, number of grains per row, mass of 1,000 grains and grain yield. The herbicide, 2,4-D, when applied in mixture with glyphosate caused severe phytotoxicity symptoms on maize. Grain yield and growth characteristics were not affected by the herbicides applied alone or as a mixture. Increasing doses of 2,4-D caused severe phytotoxicity symptoms on hybrid Status VIP3. Increasing doses of glyphosate did not show phytotoxicity symptoms and are not directly correlated to any injury caused by 2,4-D in the SX 5885 VIP3 maize hybrid.

Morphophysiological characteristics of Brazilian bean genotypes related with sulfentrazone tolerance

In the bean crop there are limited options of herbicides to control eudicotyledons weeds in pre-emergence and sulfentrazone presents potential to be used in a weed management program. The aim of this study was to determine the tolerance of a large number of Brazilian bean genotypes to sulfentrazone and their relation with morphophysiological characteristics, associating it to market classes, seed size and their center of origin. It was evaluated the effect of sulfentrazone application (400 g a.i. ha^-1) in pre-emergence of 40 Brazilian bean genotypes, 36 of which were common-bean (Phaseolus vulgaris), two cowpeas (Vigna unguiculata), one adzuki bean (Vigna angularis) and one mung bean (Vigna radiata). There was high tolerance variation of the genotypes to sulfentrazone. Morphological parameters were strongly related with relative tolerance. Common bean genotypes that had medium to large seed size (cranberry and carioca) were more tolerant, while small-sized seed genotypes were more sensitive (black). Andean genotypes were more tolerant than Mesoamerican genotypes. Within the Mesoamerican group, medium-sized seed genotypes (carioca beans) were more tolerant than small-sized seed (black beans). Considering only the Vigna genera, cowpea was highly tolerant to sulfentrazone, while mung bean showed intermediary response and adzuki bean was completely sensible.

Selectivity of metsulfuron applied to soybean before sowing in different intervals and soils

This work aimed to evaluate the selectivity of the herbicide metsulfuron applied at different times on the development of soybeans grown in soils with different characteristics. The experiment was conducted in a randomized block design, in a factorial scheme (4 x 4), with four replicates. Factor A was application time (0, 15, 30, and 45 days before sowing, DBS) and factor B was soil type (Erechim, Itaqui, Piratini, and Santa Maria). Soybean plants cultivated in the Erechim soil showed moderate phytotoxicity, with greater damage to the leaf area and plant dry matter, mainly after application at 30 DBS. Those cultivated in Itaqui soil showed gradual phytotoxicity between 14 and 28 days after emergence (DAE). Soybean plants grown in the Piratini and Santa Maria soils showed the highest phytotoxicity and photosynthetic reduction, mainly at 15 and 0 DBS. Metsulfuron application at 45 DBS caused reduced plant growth by up to 40%, and reduced shoot development (30%) in soybean plants grown in Piratini and Santa Maria soils, respectively. There were gradual changes in phytotoxicity and the morphophysiological traits of soybean plants exposed to the residual effect of metsulfuron in different soils, which indicates that soybeans should be sown more than 45 days after the application of metsulfuron, regardless of soil characteristics.

Mobility and environmental monitoring of pesticides in the atmosphere - a review

Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.

Remedial capacity of diclosulam by cover plants in different edaphoclimatic conditions

Pre-emergent herbicides have been developed for their long residual effect; however, they can make sensitive successor cultures unfeasible. Waste remediation techniques are needed for sustainable agricultural systems; for this, the edaphoclimatic asymmetries in the country must be considered. This study aimed to evaluate the remedial capacity of the herbicide diclosulam by covering crops under different edaphoclimatic conditions. Treatments were arranged in an n × 2 factorial scheme, the first factor being the number of plant species in each location and the second being the presence or absence of diclosulam in the soil. The physiological and growth characteristics of 15 potential phytoremediation species were evaluated. Herbicide residues in the environment were positively correlated with the soil pH; organic matter, aluminum, and silt contents; and aluminum saturation. The effectiveness of phytoremediation varied between species and between regions. Plant species suitable for efficient phytoremidation systems of diclosulam residues were Canavalia ensiformis for Couto Magalhães de Minas, Cajanus cajan and Canavalia ensiformis for Diamantina, Raphanus sativus for Erechim and Cajanus cajan for São João Evangelista.

Weed management in glyphosate-resistant maize

ABSTRACT The application of glyphosate associated with other herbicides is an important alternative for weed control in maize, to increase control spectrum and to minimize problems with resistance and tolerance from some species to the product. The objective of this work was to evaluate the efficacy, selectivity and effects on the grain yield components of glyphosate-resistant maize as a function of its application, associated or not with other pre- and postemergence herbicides. The design used was randomized blocks with four replications. Treatments consisted in the use of glyphosate combined with the herbicides: atrazine, [atrazine + simazine], [atrazine + oil], [atrazine + S-metolachlor], applied pre- and/or postemergence and [nicosulfuron + mesotrione] only postemergence, plus two controls, one weeded and one infested. The evaluated variables were maize phytotoxicity, weed control, ear insertion height, number of rows per ear, number of grains per row, one thousand grain mass and grain yield. Herbicide treatments caused low phytotoxicity to maize, less than 6%; control greater than 88, 95 and 95% for alexandergrass, turnip and sunflower, respectively, and did not affect grain yield components. The tested herbicides are selective to the hybrid Forseed 2A521 PW and effective in weed control. Weed control with weeding or herbicide increased maize Forseed 2A521 PW yield by 43%. The association of glyphosate with pre- or postemergence herbicides increased maize grain yield by approximately 14%.

New perspectives for weeds control using autochthonous fungi with selective bioherbicide potential

The prospection of bioherbicides has been an alternative to weed control, aiming at mitigating chemical risks to human, animal and environmental health due to extreme use of synthetic herbicides. In the present study, various fungi were isolated from plants with symptoms of fungal diseases for bioherbicide purposes against weeds (Urochloa plantaginea, Euphorbia heterophylla and Bidens pilosa). Fungi isolated were identified by molecular methods and enzymatic products obtained by fungi fermentation (cellulase, lipase, peroxidase, and amylase) were quantified. Bioherbicide selectivity study was performed on crops (soybean and corn), as well as on resistant weeds. Among the isolated fungi, Fusarium oxysporum, Fusarium ploriferatum, and Trichoderma koningiopsis presented bioherbicide potential. T. koningiopsis, in particular, presented the highest effect on Euphorbia heterophylla (popular name - Mexican fire plant), causing up to 60% of foliar damage, without presenting phytotoxicity against corn crop. New perspectives for weeds control and their use in corn crops were prospected, considering the bioherbicide selectivity described in this study.

Competitive interaction and economic injury level of Urochloa plantaginea in corn hybrids

ABSTRACT Identifying the competitive ability of corn hybrids and the economic injury level (EIL) caused by Urochloa plantaginea is important for the adoption of integrated management of this weed. This work aims to evaluate the interference and EIL of U. plantaginea infesting corn hybrids. Treatments included the corn hybrids Syngenta Status VIP3, Syngenta SX8394 VIP3, Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021, as well as 12 densities of U. plantaginea for each hybrid. We used a rectangular hyperbolic model to describe the relationship between corn grain productivity loss and the explanatory variables — plant density (PD), dry mass (DM) of the aerial parts, ground cover (GC), and leaf area (LA). EIL was determined using grain productivity, control cost, corn price, and herbicide efficacy. The rectangular hyperbolic model provides a satisfactory estimate of grain productivity loss regarding the interference of U. plantaginea in corn culture. The hybrids Pioneer 30F53 YH and Pioneer P1630H presented better competitiveness and higher EIL. Sowing the hybrids Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021 increased EIL, justifying the adoption of control measures for U. plantaginea at higher densities.

Acute and chronic toxicity of pesticides on tadpoles of Physalaemus cuvieri (Anura, Leptodactylidae)

Brazil is the largest consumer of pesticides in the world. However, knowledge on how these pesticides affect wildlife is scarce. Among the vertebrates, amphibians are particularly important in research to assess the impact of pesticides because of the correlation between pesticide and the decline of these species. This study aimed to evaluate the acute and chronic toxicity of commercial formulations of pesticides, i.e., atrazine (herbicide), cypermethrin (insecticide), and tebuconazole (fungicide) in Physalaemus cuvieri tadpoles. Eggs were collected in nature and cultivated under controlled conditions in the laboratory. Toxicity tests were carried out under standard conditions to determine the lethal concentration (LC₅₀) after 96 h of exposure and to determine the effect of sublethal concentrations after 7 days. In addition, we performed swimming activity tests on tadpoles exposed to sublethal concentrations. The lethal concentration (LC₅₀) was 19.69 mg/L for atrazine, 0.24 mg/L for cypermethrin and 0.98 mg/L for tebuconazole. In the acute test, atrazine showed lower toxicity than cypermethrin and tebuconazole for P. cuvieri. Swimming activity was affected at sublethal doses of atrazine and cypermethrin, but was not after exposure to tebuconazole. Cypermethrin was the insecticide that most altered the swimming activity of the individuals tested. The risk evaluation analysis indicated risks for tadpoles exposed to three tested pesticides, specially cypermethrin.