RESUMO

Since sugarcane is semi-perennial, it has no escape from water stresses in the Brazilian Cerrado, and consequently, drought impacts plant growth and industrial quality. The objective of this study was to evaluate the morphophysiology and quality of the first ratoon of two sugarcane varieties submitted to irrigated and stressed treatments under field conditions. For the biometric characteristics, in general, significant decreases were observed under the stressed treatment for all periods, and only minor differences were detected between the studied cultivars. Physiological parameters decreased under stressed conditions, but to a different extent between the varieties. RB855536 was able to maintain a greater rate of transpiration. Productivity was reduced by 103 t ha-1 for variety RB855536 and 121 t ha-1 for RB867515, compared to plants with full irrigation during the dry period, but cane quality was similar in both genotypes. Measurements of physiological and morphological parameters may prove useful in the rapid identification of genotypes with greater tolerance to abiotic stress.

RESUMO

The objectives of this study were to estimate the residual and half-life of [imazapic + imazapyr] and to infer on the impact of these residuals over time. The first experiment comprised the application of [imazapic + imazapyr] to Clearfield® rice. On the following summer cropping season (365 days later), undeformed soil samples 0-5 cm depth were collected and seeds of six species or varieties were sown as bioindicators of residuals (experiment 2), being assessed plant height and dry mass 20 days after emergence start. The third experiment comprised the cultivation of the same species submitted to ten increasing herbicide doses (0-280 g ha-1) to establish standard response curves, also assessing plant height and dry mass 20 days after emergence start. About 2.1-5.8% of the applied imazapic remains in soil after one year, for the label doses. Imazapyr was considered to be at negligible doses as its half-life is short, and less than 0.0000001% of the applied dose is expected to be in soil 365 days later. The expected imazapic half-life in lowland areas of Southern Brazil is longer than for dryland, being estimated as between 63 and 77 days (95% confidence interval), contrasting to the 60 days half-life previously estimated for dryland soils.

Assuntos

RESUMO

Rice is a crop that presents sensitivity to cold, especially in the germination phase, which leads to high economic losses. Alternative management forms are essential to increase tolerance to low temperatures, and seed priming represents a promising tool. The objective of this study was to investigate the priming effect of the aqueous extract of carrot roots on rice seeds to increase tolerance to low temperatures during germination. Seeds from cultivars BRS Querência (cold-susceptible) and Brilhante (cold-tolerant) were soaked for 24 h in concentrations of 0, 25, 50, and 100% carrot extract, sown on germitest paper and conditioned in BOD for 21 days at 15 °C. As a control, the seeds soaked in water were also germinated at 25 °C. They were evaluated for germination, first germination count, and germination speed index to calculate the stress indices: tolerance index, susceptibility index, and harmonic mean. They were also evaluated for the length and dry mass of shoot and root. The results showed that the rice seeds conditioning in carrot extract effectively reduces the damage caused by cold, significantly increasing the germination speed and the percentage of final germination and the growth evaluations, more expressive at 100% concentration. The stress indexes are efficient in estimating the tolerance of the cultivars and the effect of the different conditions in low-temperature conditions, highlighting the superiority of the Brilhante cultivar.

Assuntos

RESUMO

ABSTRACT This study aimed to evaluate the radiosensitivity of castor bean seeds after applications of different doses of Cobalt60 gamma radiation. Seeds were pre-soaked for 24 hours in distilled water and then irradiated with 50, 100, 150, and 200 Gy, except the control. Sowing was performed in trays, which contained soil as substrate and were maintained in a greenhouse. The electrical conductivity, emergence, emergence speed index, growth parameters and activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, and catalase) were evaluated in the leaves and roots of castor bean seedlings. Gamma radiation did not affect the electrical conductivity of the seeds; however, at a dose of 200 Gy, the emergence and emergence speed index of the seedlings was negatively affected. An analysis of the morphophysiological parameters revealed a reduction in seedling size as the radiation dose increased. There was a significant increase in superoxide dismutase and ascorbate peroxidase activities at higher radiation doses in the leaves, but not in roots. Thus, the analysis of all the variables suggests a response pattern as to the morphophysiological and biochemical changes of castor bean seedlings due to the increase of gamma radiation, which may serve as a tool for generating greater genetic variability.

Assuntos

RESUMO

This study aimed to evaluate the radiosensitivity of castor bean seeds after applications of different doses of Cobalt60 gamma radiation. Seeds were pre-soaked for 24 hours in distilled water and then irradiated with 50, 100, 150, and 200 Gy, except the control. Sowing was performed in trays, which contained soil as substrate and were maintained in a greenhouse. The electrical conductivity, emergence, emergence speed index, growth parameters and activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, and catalase) were evaluated in the leaves and roots of castor bean seedlings. Gamma radiation did not affect the electrical conductivity of the seeds; however, at a dose of 200 Gy, the emergence and emergence speed index of the seedlings was negatively affected. An analysis of the morphophysiological parameters revealed a reduction in seedling size as the radiation dose increased. There was a significant increase in superoxide dismutase and ascorbate peroxidase activities at higher radiation doses in the leaves, but not in roots. Thus, the analysis of all the variables suggests a response pattern as to the morphophysiological and biochemical changes of castor bean seedlings due to the increase of gamma radiation, which may serve as a tool for generating greater genetic variability.

Assuntos

RESUMO

This study aimed to evaluate the mechanisms of flood tolerance of the root system of Erythrina crista-galli L. plants by measuring the activity of antioxidant enzymes and oxidative stress components in the leaves and roots. Additionally, the activity of fermentation enzymes in the roots was measured. The following two treatments were used: plants with flooded roots, which were maintained at a given water level above the soil surface, and non-flooded plants, which were used as the control. The measurements were performed at 10, 20, 30, 40, and 50 days after treatment. The following parameters were evaluated at each time-point: the activities of superoxide dismutase, catalase and ascorbate peroxidase, the quantification of lipid peroxidation and hydrogen peroxide (H2O2) content in the leaves, roots, and adventitious roots, and the activities of lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase in both the primary and adventitious roots. There was an increase in the activity of catalase and ascorbate peroxidase in the leaves to maintain stable H2O2 levels, which reduced lipid peroxidation. In the roots, higher activity of all antioxidant enzymes was observed at up to 30 days of flooding, which favoured both reduced H2O2 levels and lipid peroxidation. Activity of the fermentation enzymes was observed in the primary roots from the onset of the stress conditions; however, their activity was necessary only in the adventitious roots during the final periods of flooding. In conclusion, E. crista-galli L. depends on adventitious roots and particularly on the use of the fermentation pathway to tolerate flood conditions.(AU)

O objetivo deste trabalho foi determinar os mecanismos de tolerância ao alagamento de plantas de Erythrina crista-galli L., por meio da avaliação da atividade de enzimas antioxidantes e fermentativas, assim como dos componentes do estresse oxidativo em folhas e raízes. Plantas oriundas de sementes foram cultivadas em vasos com capacidade para 0,5 litros em casa de vegetação e transferidas para vasos de cinco litros. Foram utilizados dois tratamentos: plantas alagadas nas raízes com a manutenção de uma lâmina de água acima da superfície do solo e plantas não alagadas (controle). As avaliações foram realizadas aos 10, 20, 30, 40 e 50 dias após a indução dos tratamentos. O delineamento experimental utilizado foi em blocos ao acaso e os resultados obtidos submetidos à análise de variância e analisados por comparação de médias pelo Teste de Tukey. Em cada período foram avaliadas a atividade de superóxido dismutase, catalase, ascorbato peroxidase, quantificação da peroxidação lipídica e teores de peróxido de hidrogênio em folhas, raízes e raízes adventícias; a atividade das enzimas lactato desidrogenase, piruvato descarboxilase e álcool desidrogenase nas raízes principais e adventícias. Foi verificado um aumento na atividade das enzimas ascorbato peroxidase e catalase nas folhas para manter estáveis os níveis de H2O2, o que proporcionou redução na peroxidação lipídica. Nas raízes foi verificada uma atuação mais marcante de todas as enzimas antioxidantes até os 30 dias de alagamento, favorecendo a redução nos níveis de H2O2 e de peroxidação de lipídios. A atividade das enzimas fermentativas foi evidenciada nas raízes principais desde o início do estresse, porém nas raízes adventícias só foi requerida nos períodos finais. Pode-se concluir que a E. crista-galli L., depende das raízes adventícias e, em especial, da utilização da rota fermentativa para tolerar a condição de alagamento.(AU)

Assuntos

RESUMO

This study aimed to evaluate the mechanisms of flood tolerance of the root system of Erythrina crista-galli L. plants by measuring the activity of antioxidant enzymes and oxidative stress components in the leaves and roots. Additionally, the activity of fermentation enzymes in the roots was measured. The following two treatments were used: plants with flooded roots, which were maintained at a given water level above the soil surface, and non-flooded plants, which were used as the control. The measurements were performed at 10, 20, 30, 40, and 50 days after treatment. The following parameters were evaluated at each time-point: the activities of superoxide dismutase, catalase and ascorbate peroxidase, the quantification of lipid peroxidation and hydrogen peroxide (H2O2) content in the leaves, roots, and adventitious roots, and the activities of lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase in both the primary and adventitious roots. There was an increase in the activity of catalase and ascorbate peroxidase in the leaves to maintain stable H2O2 levels, which reduced lipid peroxidation. In the roots, higher activity of all antioxidant enzymes was observed at up to 30 days of flooding, which favoured both reduced H2O2 levels and lipid peroxidation. Activity of the fermentation enzymes was observed in the primary roots from the onset of the stress conditions; however, their activity was necessary only in the adventitious roots during the final periods of flooding. In conclusion, E. crista-galli L. depends on adventitious roots and particularly on the use of the fermentation pathway to tolerate flood conditions.

O objetivo deste trabalho foi determinar os mecanismos de tolerância ao alagamento de plantas de Erythrina crista-galli L., por meio da avaliação da atividade de enzimas antioxidantes e fermentativas, assim como dos componentes do estresse oxidativo em folhas e raízes. Plantas oriundas de sementes foram cultivadas em vasos com capacidade para 0,5 litros em casa de vegetação e transferidas para vasos de cinco litros. Foram utilizados dois tratamentos: plantas alagadas nas raízes com a manutenção de uma lâmina de água acima da superfície do solo e plantas não alagadas (controle). As avaliações foram realizadas aos 10, 20, 30, 40 e 50 dias após a indução dos tratamentos. O delineamento experimental utilizado foi em blocos ao acaso e os resultados obtidos submetidos à análise de variância e analisados por comparação de médias pelo Teste de Tukey. Em cada período foram avaliadas a atividade de superóxido dismutase, catalase, ascorbato peroxidase, quantificação da peroxidação lipídica e teores de peróxido de hidrogênio em folhas, raízes e raízes adventícias; a atividade das enzimas lactato desidrogenase, piruvato descarboxilase e álcool desidrogenase nas raízes principais e adventícias. Foi verificado um aumento na atividade das enzimas ascorbato peroxidase e catalase nas folhas para manter estáveis os níveis de H2O2, o que proporcionou redução na peroxidação lipídica. Nas raízes foi verificada uma atuação mais marcante de todas as enzimas antioxidantes até os 30 dias de alagamento, favorecendo a redução nos níveis de H2O2 e de peroxidação de lipídios. A atividade das enzimas fermentativas foi evidenciada nas raízes principais desde o início do estresse, porém nas raízes adventícias só foi requerida nos períodos finais. Pode-se concluir que a E. crista-galli L., depende das raízes adventícias e, em especial, da utilização da rota fermentativa para tolerar a condição de alagamento.

Assuntos

RESUMO

Techniques used to induce mutations, such as ionizing radiation, are an effective tool in increasing genetic variability in breeding programs of species of economic interest. This study aimed to evaluate the effect of different doses of Co60 gamma radiation on previously soaked seeds on the emergence and early growth of seedlings of two rice cultivars. To do this, seeds (25 percent moisture) of BRS Querência and BRS Fronteira were irradiated with zero (control), 50, 100, 150 and 200 Gy, and then sown in trays containing soil and kept in a greenhouse. The results showed that gamma radiation affected seedling development, where the highest dose tested (200 Gy) significantly reduced the emergence and the index of emergence speed. Growth parameters were reduced greater reduction in cv. BRS Querência. For antioxidant enzymes, superoxide dismutase expressed little variation for the periods evaluated. Already ascorbate peroxidase and catalase showed a significant increase in horsepower cv. BRS Fronteira at 14 DAS, followed by an increase in both cultivars ascorbate peroxidase activity at 28 DAS. The highest antioxidant capacity observed in cv. BRS Fronteira conferred greater tolerance to stress caused by gamma radiation.

Técnicas como radiações ionizantes, utilizadas para induzir mutações constituem ferramenta eficaz no aumento de variabilidade genética em programas de melhoramento de espécies de interesse econômico. Neste trabalho, objetivou-se verificar o efeito de diferentes doses de radiação gama Co60 em sementes previamente embebidas sobre a emergência e o crescimento inicial de plântulas de duas cultivares de arroz. Lotes de sementes com 25 por cento de umidade das cultivares BRS Querência e BRS Fronteira foram irradiados com doses de zero (controle), 50, 100, 150 e 200 Gy, sendo, em seguida, semeadas em bandejas contendo solo e mantidas em casa de vegetação. Os resultados mostraram que a radiação gama afetou o desenvolvimento das plântulas, sendo que a maior dose testada (200 Gy) reduziu, significativamente, a emergência e o índice de velocidade de emergência. Os parâmetros de crescimento apresentaram maior redução na cv. BRS Querência. Na atividade das enzimas antioxidantes, a superóxido dismutase expressou pouca variação para os períodos avaliados. Já, a ascorbato peroxidase e catalase mostraram expressivo aumento na cv. BRS Fronteira aos 14 DAS, seguidas de incremento para as duas cultivares na atividade da ascorbato peroxidase aos 28 DAS. A maior capacidade antioxidante observada na cv. BRS Fronteira conferiu uma maior tolerância ao estresse causado pela radiação gama.

RESUMO

Coffee (Coffea arabica) plants show a positive relationship between stomatal closure and formation and accumulation of H2O2. However, for coffee plants under water restriction such relationship has never been studied. The objective of the present study was evaluate the stomatal movement and the antioxidant capacity of coffee seedlings under different water regimes. Eight months old coffee seedlings of cv. Catuaí IAC 99 were submitted to field capacity, gradual and total suspension of irrigation during a period of 21 days. Evaluations of leaf water potential (w) were performed in the beginning of the morning, and stomatal resistance, transpiration rate and vapor pressure deficit were determined at 10 am and 5 pm. All biochemical and enzymatic determinations were performed in leaves collected at 5 pm. Evaluations and samplings were performed at three days intervals. There was no variation in w during the evaluated period for plants in field capacity. However, an expressive decrease of w following day 12, reaching values near -2.5 MPa at the end of the experiment was observed for plants submitted to gradual suspension of irrigation. For plants submitted to total suspension of irrigation, w decreases after the sixth day, reaching -2.5 MPa at day 15. The decay of w in plants submitted to gradual and total suspension of irrigation reflected in increased stomatal resistance and in a decreased transpiration rate leading to an increase in hydrogen peroxide formation and, on final stages, increase in lipid peroxidation. As a conclusion, an increase in the activity of antioxidant enzymes as well as in the levels of ascorbate and dehydroascorbate was observed, which act in the detoxification of free radicals formed as result of the water stress.

Para o cafeeiro (Coffea arabica) existe uma comprovada relação positiva entre fechamento estomático e formação e acúmulo de H2O2. Entretanto, tal relação para a cultura sob restrição hídrica ainda não foi estudada. Avaliou-se o movimento estomático e a capacidade antioxidante em mudas de cafeeiro sob diferentes regimes hídricos. Mudas de cafeeiro cv. Catuaí IAC 99, com oito meses de idade, foram submetidas à capacidade de campo, suspensão gradativa e suspensão total da irrigação por um período de 21 dias. Foram realizadas avaliações do potencial hídrico (w) foliar na antemanhã e resistência estomática, taxa transpiratória e déficit de pressão de vapor foram avaliados as 10h00 e 17h00. As determinações bioquímicas e enzimáticas foram realizadas em folhas coletadas às 17h00. Todas as avaliações e coletas foram realizadas em intervalos de três dias. Nas plantas em capacidade de campo não houve variação no w durante o período de avaliação. Para a suspensão gradativa da irrigação, houve queda expressiva a partir dos 12 dias, chegando próximo a -2,5 Mpa, ao final do experimento. Já nas plantas em suspensão total da irrigação observou-se queda no w a partir do sexto dia, chegando a -2,5 MPa aos 15 dias. A queda no w para as plantas em suspensão gradual e total da irrigação refletiu em aumentos na resistência estomática e diminuição da taxa transpiratória, ocasionando aumento na formação de peróxido de hidrogênio e nos períodos finais, aumentos na peroxidação de lipídios. Em conseqüência obervaram-se aumentos na atividade das enzimas antioxidantes, bem como nos teores de ascorbato e dehidroascorbato, atuando na detoxificação dos radicais livres formados em função do estresse.

RESUMO

Coffee (Coffea arabica) plants show a positive relationship between stomatal closure and formation and accumulation of H2O2. However, for coffee plants under water restriction such relationship has never been studied. The objective of the present study was evaluate the stomatal movement and the antioxidant capacity of coffee seedlings under different water regimes. Eight months old coffee seedlings of cv. Catuaí IAC 99 were submitted to field capacity, gradual and total suspension of irrigation during a period of 21 days. Evaluations of leaf water potential (w) were performed in the beginning of the morning, and stomatal resistance, transpiration rate and vapor pressure deficit were determined at 10 am and 5 pm. All biochemical and enzymatic determinations were performed in leaves collected at 5 pm. Evaluations and samplings were performed at three days intervals. There was no variation in w during the evaluated period for plants in field capacity. However, an expressive decrease of w following day 12, reaching values near -2.5 MPa at the end of the experiment was observed for plants submitted to gradual suspension of irrigation. For plants submitted to total suspension of irrigation, w decreases after the sixth day, reaching -2.5 MPa at day 15. The decay of w in plants submitted to gradual and total suspension of irrigation reflected in increased stomatal resistance and in a decreased transpiration rate leading to an increase in hydrogen peroxide formation and, on final stages, increase in lipid peroxidation. As a conclusion, an increase in the activity of antioxidant enzymes as well as in the levels of ascorbate and dehydroascorbate was observed, which act in the detoxification of free radicals formed as result of the water stress.

Para o cafeeiro (Coffea arabica) existe uma comprovada relação positiva entre fechamento estomático e formação e acúmulo de H2O2. Entretanto, tal relação para a cultura sob restrição hídrica ainda não foi estudada. Avaliou-se o movimento estomático e a capacidade antioxidante em mudas de cafeeiro sob diferentes regimes hídricos. Mudas de cafeeiro cv. Catuaí IAC 99, com oito meses de idade, foram submetidas à capacidade de campo, suspensão gradativa e suspensão total da irrigação por um período de 21 dias. Foram realizadas avaliações do potencial hídrico (w) foliar na antemanhã e resistência estomática, taxa transpiratória e déficit de pressão de vapor foram avaliados as 10h00 e 17h00. As determinações bioquímicas e enzimáticas foram realizadas em folhas coletadas às 17h00. Todas as avaliações e coletas foram realizadas em intervalos de três dias. Nas plantas em capacidade de campo não houve variação no w durante o período de avaliação. Para a suspensão gradativa da irrigação, houve queda expressiva a partir dos 12 dias, chegando próximo a -2,5 Mpa, ao final do experimento. Já nas plantas em suspensão total da irrigação observou-se queda no w a partir do sexto dia, chegando a -2,5 MPa aos 15 dias. A queda no w para as plantas em suspensão gradual e total da irrigação refletiu em aumentos na resistência estomática e diminuição da taxa transpiratória, ocasionando aumento na formação de peróxido de hidrogênio e nos períodos finais, aumentos na peroxidação de lipídios. Em conseqüência obervaram-se aumentos na atividade das enzimas antioxidantes, bem como nos teores de ascorbato e dehidroascorbato, atuando na detoxificação dos radicais livres formados em função do estresse.