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Current climate change scenarios require strategies that mitigate the effects of water deficits. Given that chitosan stimulates induced resistance responses, we tested the hypothesis that foliar application of this polysaccharide can have positive effects on the primary metabolite, antioxidant, and osmoregulatory metabolisms of sorghum, mitigating the effects of water deficit on grain yield. Sorghum plants were cultivated under either irrigated or water-deficit conditions and were either treated or untreated with chitosan, and we assessed the following responses: water potential, gas exchange, nutritional status, biosynthesis of primary and osmoregulatory metabolites, the activity of the antioxidant system constituents, and hydrogen peroxide and malondialdehyde contents. An active methodology was used to impose water stress on plants grown in pots with 20 kg of soil, 06 replications per treatment. Sorghum plants subjected to water deficit that were treated with chitosan exhibited higher stomatal conductance and transpiration than the untreated plants. Water restriction reduced the nutrient contents of leaves, but in the irrigated plants, chitosan treatment increased the tissue contents of certain nutrients and leaf concentrations of total proteins and total amino acids. In the plants under water-deficit conditions that were treated with chitosan, an elevated photosynthetic rate contributed to an increase in carbohydrate accumulation and a higher production of panicle and grain dry biomass compared with the untreated plants. The activity of catalase and ascorbate peroxidase also increased in response to chitosan. Overall, chitosan was effective in enhancing the water deficit tolerance of sorghum plants cultivated under water-deficit conditions by 57%. With this work, we generate perspectives for studies focusing on the development of water-deficit-resistant sorghum lineages, by means of chitosan elicitation.

The objective was to evaluate the effect of the glyphosate on Hymenaea courbaril L. A randomized block design with five replications was implemented. Each experimental unit was composed of one plant in a 5 L container. The treatments were 0 “control”; 96; 240; 480; and 960 g ha−1 “corresponding to 10, 25, 50, and 100% of the commercial dose of glyphosate recommended for Caryocar brasiliense crop, respectively”. The evaluations were performed at 24 h and 60 days after application. Visual and anatomical evaluations did not change regardless of the dose, while the histochemical evaluation showed an accumulation of starch grains in leaf tissues. There was an increase in the photosynthetic rate, in the electron transport rate, and in the effective quantum yield of photosystem II at 24 h after application. At 60 days after the application of the treatments, the photosynthetic rate showed a slight decrease and the transpiratory rate showed quadratic behavior. An increase in plant height was observed up to the dose of 480 g ha−1, a linear increase in stem diameter and a decrease in the number of leaves with increasing glyphosate doses. These results show that the cuticle protected the plant, and that the little absorbed glyphosate increased photosynthesis and transpiration to favor the plants. We can conclude that the H. courbaril species is able to survive after contact with glyphosate during the evaluated time, with no visual and/or anatomical damage, showing increases in growth and physiological characteristics for the tested doses.

The expansion of land use for agricultural interests and the excessive use of herbicides are among the causes of biodiversity losses in the Brazilian Cerrado biome. Therefore, we aimed to test the hypothesis that Dipteryx alata Vogel, a common species in this biome, is sensitive to nicosulfuron because of its high phytotoxicity. We evaluated physiological, biochemical and morphological responses in D. alata plants exposed to increasing doses of the herbicide. Young plants were transplanted to 10 L pots containing substrate composed of soil and sand (2:1) after fertilization. After an acclimation period, the following doses of nicosulfuron were applied: 0 (control), 6, 12, 24, 48, and 60 g a.e. ha−1. The experiment was conducted in a randomized block design factorial scheme with six doses of nicosulfuron, three evaluation times, and five replicates per treatment. The effects of the herbicide were assessed by measuring gas exchange, chlorophyll a fluorescence, photosynthetic pigments, membrane permeability, antioxidant enzymes and acetolactate synthase. Nicosulfuron altered the photosynthetic machinery and enzymatic metabolism of D. alata. Reductions in physiological traits, increased catalase and ascorbate peroxidase activities, enhanced malondialdehyde concentrations rate of electrolyte leakage and decreased acetolactate synthase activity in response to nicosulfuron all suggest that D. alata is sensitive to this herbicide.

ABSTRACT The herbicide tembotrione may be seletivity to sorghum, which is of utmost importance in grain production systems. Thus, the present study aimed to evaluate the selectivity of tembotrione + atrazine combinations applied post-emergence at different phenological stages of grain sorghum. Four experiments were carried out in Rio Verde and Montividiu (state of Goiás) in succession to soybean cultivation in 2017 and 2018. The experiments were carried out in randomized block design with six replications, both in a (3x2) + 1 factorial arrangement. The first factor referred to three vegetative stages of application (V3, V5 and V7) associated with two doses of tembotrione (90 and 180 g ha-1) combined with atrazine (1,000 g ha-1)and and an additional treatment with no herbicide application. Tembotrione + atrazine applications at the V7 stage caused less damage to grain yield and dry mass accumulation in relation to V3 and V5. The dose of 90 g ha-1 tembotrione + atrazine combined with atrazine resulted in higher grain yields compared to 180 g ha-1, although still at lower levels compared to the treatment with no herbicides. Thus, herbicide tembotrione at doses of 90 and 180 g ha-1 combined with atrazine did not have selectivity for grain sorghum in applications at V3, V5 and V7 stages.

The objective of this study was to evaluate the the ability of foliar application of potassium nitrate (KNO3) to induce water deficit tolerance in sorghum plants (Sorghum bicolor cv. P898012) subjected to water deficit at pre-flowering. The experiment was conducted under greenhouse conditions with 4 treatments: field capacity (FC), water deficit (WD), field capacity + KNO3 (FC + KNO3), and water deficit + KNO3 (WD + KNO3). Two foliar applications of 3% (m/v) KNO3 were made, the first on day zero of stress and the second on the fifth day. All analyses were performed after 12 days of stress (end of stress). Foliar application of KNO3 to irrigated plants led to increases in relative chlorophyll content, photosynthetic rate, stomatal conductance, transpiration, and carboxylation efficiency. It also induced increases in leaf concentrations of P, Mg, S, Cu, and Fe, in addition to height growth. Under water deficit conditions, plants treated with KNO3 presented higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency, and higher levels of P, K, Mg, S, Cu, and Fe than those not treated with KNO3. The morphometry of the root system was not altered by the treatments. In addition, plants treated with KNO3 under water deficit conditions showed higher growth and a grain yield 32.2% higher than those that did not receive KNO3. These results demonstrated that KNO3 applied to the leaves induced water deficit tolerance in sorghum plants subjected to severe water stress at pre-flowering.

The aim of this study was to evaluate the effects of pre-harvest desiccant herbicides on the yield and the physiological and technological quality of cowpea seeds after harvest and after storage. The experiment was conducted in a randomized block design with four replications. A split-plot design (6 × 2) was composed of the desiccant herbicides flumioxazin (30 g ai.ha-1), glufosinate ammonium (500 g ai.ha-1), paraquat (400 g ai.ha-1), saflufenacil (70 g ai.ha-1), and carfentrazone (24 g ai.ha-1) and an untreated control, as well as two seed evaluation periods, at harvest and six months after h arvest. Desiccants were applied at the R5 stage. The desiccants affected the yield, classification, color, and physiological quality of seeds of ‘BRS Guariba’. The glufosinate ammonium and paraquat herbicides compromised seed physiological quality. Flumioxazin did not affect seed yield components, color, and physiological quality. Storage at 20 °C for six months affected seed physiological quality. Resumo: O objetivo deste estudo foi avaliar os efeitos de herbicidas dessecantes aplicados em pré-colheita sobre o rendimento, a qualidade fisiológica e tecnológica de sementes de feijão-caupi após a colheita e o armazenamento. O experimento foi conduzido em delineamento de blocos ao acaso, com quatro repetições. Adotou-se o esquema de parcelas subdivididas (6 x 2), compostas pelos herbicidas dessecantes: flumioxazim (30 g i.a.ha-1), glufosinato de amônio (500 g i.a.ha-1), paraquate (400 g i.a.ha-1), saflufenacil (70 g i.a.ha-1), carfentrazone (24 g i.a.ha-1) e uma testemunha não tratada, por duas épocas de avaliação das sementes: colheita e seis meses após a colheita. A aplicação dos dessecantes ocorreu no estágio R5. Os dessecantes afetaram o rendimento, a classificação, a coloração e a qualidade fisiológica das sementes da cultivar BRS Guariba. Os herbicidas glufosinato de amônio e paraquate comprometeram a qualidade fisiológica das sementes. O flumioxazin não afetou os componentes de rendimento, a coloração e a qualidade fisiológica. O armazenamento a 20 °C por seis meses afetou a qualidade fisiológica das sementes.

This study aimed to evaluate the response of Toona ciliata seedlings to sublethal doses of glyphosate. The increasing use of glyphosate in agriculture concerns the scientific community, as the drift of this pollutant into aquatic systems or atmospheric currents can affect non-target species. Therefore, we need to understand how non-target species respond to small doses of this herbicide. T. ciliata seedlings (clone BV-1110) were exposed to sublethal doses of glyphosate (0, 9.6, 19.2, 38.4, 76.8 g ae ha−1). Anatomical, physiological, and photochemical analyses were performed 60 days after herbicide application, and growth assessments were carried out after 160 days of cultivation. We found that sublethal doses of glyphosate above 19.2 g ae ha−1 induced toxicity symptoms in Toona ciliata leaves. These symptoms were mild in some cases, such as chlorosis, but severe in other cases, such as tissue necrosis. We observed a positive relationship between increased plant height and photochemical yield with plant exposure to sub-doses 9.6 and 19.2 g ae ha−1. A sublethal dose of 38.4 g ae ha−1 improved the photosynthetic rate and carboxylation efficiency. Thus, we confirmed the hypothesis of a hormetic effect when T. ciliata was exposed to sub-doses of glyphosate equal to or lower than 38.4 g ae ha−1. However, the sublethal dose of 76.8 g ae ha−1 must be considered toxic, impacting photosynthetic activity and, consequently, the height of T. ciliata. The stem diameter of T. ciliata responded positively to increasing glyphosate doses. This occurs to compensate for the negative effect of glyphosate on water absorption. Further research will provide valuable information for harnessing the potential benefits of hormesis to improve the productivity of T. ciliata.

The excessive use of agrochemicals negatively impacts the environment, making the development of sustainable technologies for the reduction of contaminants in soil necessary. Hexazinone is the herbicide most used for sugarcane crops and persists in the environment. Moreover, its main route of degradation in the soil is through microorganisms. Therefore, six microorganisms were selected that presented growth in the presence of the herbicide; SCR1 - Microbacterium arborescens; SCR2 - Bacillus pumilus; SCM3 - Stenotrophomonas maltophilia; SCM4 - Bacillus cereus; SCM5A - M. arborescens; and SCM5B - B. safensis. A test was performed to evaluate the ability of each lineage in phosphate solubilization. For the Ca3(PO4)2 solubilization test, the strains that showed the best results were B. pumilus and S. maltophilia. Subsequently, the inoculants were prepared and the concentrations after plating were 2.71 × 109 CFU mL-1 for B. pumilus, 1.02 × 109 CFU mL-1 for S. maltophilia, and 1.14 × 1010 CFU mL-1 for a combination of the two strains. These were satisfactory values for use as inoculants. RESUMO: O uso de agroquímicos resulta em impactos ambientais e torna-se necessário o emprego de tecnologias sustentáveis para diminuição de contaminantes no solo. O hexazinona é o herbicida mais utilizado para a cultura da cana-de-açúcar, e apresenta persistência no ambiente. A principal via de degradação no solo é por meio de microrganismos. Com isso, selecionou-se seis microrganismos que apresentaram crescimento na presença do herbicida: SCR1 - Microbacterium arborescens; SCR2 - Bacillus pumilus; SCM3 - Stenotrophomonas maltophilia; SCM4 - Bacillus cereus; SCM5A - M. arborescens; SCM5B - Bacillus safensis. Foi realizado um teste para avaliar a habilidade de cada linhagem na solubilização de fosfatos, e no caso da solubilização de Ca3(PO4)2, as linhagens que apresentaram melhores resultados foram B. pumilus e S. maltophilia. Posteriormente, os inoculantes foram preparados e a concentração após plaqueamento de 2,71x109 UFC mL-1 para B. pumilus, 1,02x109 UFC mL-1 para S. maltophilia e consórcio com as duas linhagens 1,14x1010 UFC mL-1 apresentaram valores satisfatórios para utilização como inoculantes.

The release of soybean varieties resistant to dicamba herbicide leads to the possibility of dicamba herbicide drift into soybean seed production fields and reduction in the physiological quality of soybean seeds. The aim of this study was to evaluate the physiological quality of soybean seeds as a function of the application of reduced rates of dicamba in two phenological phases. A randomized block experimental design was used, with four replications. The 4 × 2 + 1 factorial arrangement consisted of four reduced rates (0.028, 0.28, 2.8 and 28 g.ha-1) of dicamba applied in the V4 and R2 stages + a control. The physiological quality of the seeds was evaluated after harvest and at six months after storage at 20 °C. At the rate of 28 g.ha-1 of dicamba applied in the V4 and R2 stages, seed germination declined by 15% and 42%, respectively. After storage, seeds under the 28 g.ha-1 dicamba treatment had 64% lower germination compared to the lowest application rate evaluated, and electrical conductivity doubled in relation to the control. The physiological quality of soybean seeds declines under these reduced rates of dicamba applied in the V4 and R2 stages, both before and after storage. Resumo: Com a inserção de variedades de soja resistentes ao herbicida dicamba, surge a possibilidade de deriva deste herbicida em campos de produção e a ocorrência de redução na qualidade fisiológica das sementes. Objetivou-se avaliar a qualidade fisiológica das sementes de soja em função da aplicação de subdoses de dicamba em duas fases fenológicas. O delineamento foi em blocos casualizados, com quatro repetições. O esquema fatorial 4 x 2 + 1 composto por quatro doses (0,028, 0,28, 2,8 e 28 g.ha-1) de dicamba aplicados em V4 e R2 + testemunha. A qualidade fisiológica das sementes foi avaliada após a colheita e aos seis meses após armazenadas a 20 °C. Na dose de 28 g.ha-1 de dicamba aplicados em V4 e R2, as sementes apresentaram redução da germinação em 15 e 42%, respectivamente. Após o armazenamento, as sementes do tratamento com 28 g.ha-1 de dicamba apresentaram germinação 64% menor se comparado à menor dose avaliada e a condutividade elétrica duplicou em relação à testemunha. As sementes de soja têm sua qualidade fisiológica reduzida por subdoses de dicamba aplicadas nos estádios V4 e R2 tanto antes quanto após o armazenamento.

ABSTRACT The objective of this study was to evaluate the responses of Raphanus sativus to the application of the herbicide tepraloxydim by analyzing photosynthetic and biometric characteristics of the plants. The experiment was conducted in a greenhouse and treatments were instituted when the plants had five expanded leaves. The herbicide tepraloxydim was applied at doses of 0, 75, 100, and 125 g of active ingredient per hectare (g a.i. ha-1). The herbicide dose of 125 g a.i. ha-1 led to a small decrease in the photosynthetic rate, water use efficiency, effective quantum yield of PSII, rate of electron transport, and the concentration of chloroplastidic pigments in the leaves of R. sativus. On the other hand, there was a small increase in CO2 concentration in the substomatal chamber. The number of branches, leaves, flowers, plant height and dry mass of the stem and flowers were reduced more prominently in response to herbicide doses than the photosynthetic characteristics. Therefore, treatment with tepraloxydim inhibits the growth and formation of the leaves, branches and flowers of R. sativus at the stage of development analyzed. However, doses of 75, and 100 g a.i. ha-1 neither compromise the photosynthetic apparatus nor the stability of cell membranes.