Resumo: A aplicação exógena de H 2 O 2 tem demonstrado eficiência na aclimatação das plantas aos estresses bióticos e abióticos devido estimular a ativação do sistema de defesa antioxidativo. Neste sentido, objetivou-se com o trabalho avaliar a influência do método de aplicação de diferentes concentrações de H 2 O 2 sobre o crescimento inicial de plantas de milho irrigadas água salina. O experimento foi conduzido em ambiente protegido, com os tratamentos dispostos em delineamento inteiramente casualizado, em esquema fatorial 5 x 2, correspondente as concentrações de peróxido de hidrogênio (H 2 O 2 ) de 0; 5; 10; 15 e 20 µmol L -1 aplicados na semeadura via água de irrigação e, pulverização foliar aos 15 dias após a semeadura (DAS), com quatro repetições e unidade experimental constituída por um vaso de 3 L contendo duas plantas de milho híbrido 4051. As plantas foram irrigadas com água de CE de 2,0 dS m -1 . As 28 DAS verificou-se que a aplicação de H 2 O 2 na semeadura e através de pulverização foliar promove aclimatação de plantas de milho à salinidade da água de irrigação, aumentando a tolerância ao estresse salino. O maior crescimento inicial do milho é obtido nas concentrações de H 2 O 2 variando de 7 a 8 µmol L -1 , sendo mais eficiente a aplicação na semeadura. O pré-tratamento de plantas de milho com H 2 O 2 a partir de 15 µmol L -1 incrementa o estresse, promovendo maiores danos ao crescimento vegetativo. Palavras-chaves:Zea mays L., estresse salino, peróxido de hidrogênio, aclimatação. Abstract:Exogenous application of H 2 O 2 has established efficiency in acclimatization of plants to biotic and abiotic stresses due to stimulate the activation of antioxidant defense system. In this context, it was aimed with this work evaluate the effect of application method of different concentrations of H 2 O 2 on initial growth of maize plants irrigated saline water. The experiment was conducted in a greenhouse, with the treatments in a randomized completely design in a factorial 5 x 2 corresponding the hydrogen peroxide concentrations (H 2 O 2 ) 0; 5; 10; 15:20 µmol L -1 applied in sowing by irrigation water and foliar spray at 15 days after sowing (DAS), with four repetitions and experimental unit consisting of vessel a 3 L containing two plants hybrid maize 4051. The plants were irrigated with EC water of 2.0 dS m -1 . The 28 DAS it was found what the application H 2 O 2 at sowing and foliar spraying promote acclimatization of maize plants at salinity irrigation water, increasing tolerance to salt stress. The more initial growth of maize is obtained in H 2 O 2 concentrations ranging from 7 to 8 µmol L -1 , being more efficient the application at sowing. The pretreatment of maize plants with H 2 O 2 from 15 µmol L -1 increasing stress, promoting further damage to vegetative growth.
The salinity of irrigation water or soil is the abiotic factor that most negatively impacts the yield of crops, including green maize, so it is necessary to find alternatives to ensure production. In this context, this study aimed to evaluate gas exchange, photosynthetic pigments, and growth of maize under salinity of irrigation water and application of hydrogen peroxide. The experiment was conducted at the Center of Sciences and Agrifood Technology, Pombal, PB, belonging to the Federal University of Campina Grande, in the period from January to February 2015, using the maize hybrid ‘AG 1051’. The treatments consisted of two salinity levels of irrigation water (0.3 and 2.0 dS m-1) and five concentrations of hydrogen peroxide (0, 40, 80, 160, and 320 µmol L-1) applied via irrigation water. The experimental design was completely randomized, in a 2 × 5 factorial scheme, with four replicates. ECw of 2.0 dS m-1 reduces transpiration, stomatal conductance, total chlorophyll, carotenoids, and initial growth, but does not affect the dry mass accumulation of maize plants. Application of H2O2 via soil varying from 0 to 320 µmol L-1 causes reductions in the CO2 assimilation rate and transpiration, as well as at concentrations from 0 to 160 µmol L-1 for stomatal conductance of plants irrigated with ECw of 2.0 dS m-1. Application of H2O2 via soil up to a concentration of 320 µmol L-1 increases the plant height, but reduces culm diameter of maize.
In the semi-arid region of northeastern Brazil, soil and climate conditions can increase the risk of soil salinization, particularly when poor-quality water is used for irrigation. Therefore, techniques that improve the yields of melon culture under adverse conditions, such as salinity, are of great relevance to the production sector. The objective of this study was to evaluate the effectiveness of hydrogen peroxide (H2O2) in acclimatizing melon trees subjected to irrigation water with different salinity levels. The treatments consisted of irrigation water with two electrical conductivities (0.3 and 5.0 dS m-1) and four concentrations of H2O2 (0, 5, 10, and 15 µmol L-1). The experimental design used was randomized blocks, arranged in a 2 × 4 factorial scheme, with four replicates and four plants per plot. Increase in salinity of irrigation water reduced the growth, gas exchange, and production of melon plants. However, H2O2, at a concentration of 6.35 µmol L-1, yielded improvements in physiology, growth, and production, in addition to reducing the deleterious effects of saline stress on melon production.
Trabalho de dissertação de Mestrado do primeiro autor. PALAVRAS-CHAVE Citrullus lanatus Fertilizantes Fisiologia Produção Efeito residual KEYWORDS Citrulluslanatus Fertilizers Physiology Production Residual effect RESUMO: A busca por alternativas de adubação que diminuam ou até mesmo eliminem a utilização de fertilizantes minerais industrializados é uma realidade dentre os pequenos e médios produtores agrícolas nordestinos. O objetivo do trabalho foi avaliar as respostas morfofisiológicas da melancieira, em um cultivo sucessivo, à aplicação de doses de NPK, utilizando diferentes proporções de adubos minerais e orgânicos. O experimento foi realizado em uma área da Universidade Federal de Campina Grande (UFCG), Campus Pombal-PB (6º 48' 16"S e 37º 49' 15"W), durante o período de outubro de 2013 a janeiro de 2014. O delineamento foi em blocos ao acaso, com quatro repetições, dispostos em esquema fatorial 3 × 5. No fator (A), foram alocadas as doses de 50%, 100% e 150% da recomendação de NPK para melancieira e, no fator (B), cinco proporções de adubo mineral e orgânico (100/0, 75/25, 50/50, 25/75 e 0/100). A dose de 50% da recomendação de NPK favoreceu a maior atividade fotossintética das plantas de melancia no segundo ciclo de cultivo. Não houve diferença entre as concentrações de nutrientes estudadas no segundo ciclo da melancieira sobre os aspectos de produção e qualidade dos frutos, podendo-se optar pela menor concentração de nutrientes, 50%. Não houve diferença entre as proporções de adubo mineral e orgânico estudadas no segundo ciclo da melancieira sobre os aspectos de produção e qualidade dos frutos, podendo-se optar pela adubação orgânica sem perdas de rendimento.
The study aimed to assess the yield, nutrients accumulation and fruit quality of watermelon grown under different NPK rates provided by mineral and organic fertilizers. The experiment was performed at the Federal University of Campina Grande (UFCG), Campus Pombal-PB, during the period from June to September 2013. Treatments consisted of three nutrient concentrations N, P and K (50, 100 and 150% of NPK recommendation for watermelon) and five ratios of mineral and organic fertilizer (100/0, 75/25, 50/50, 25 / 75 to 0/100). The experimental design was in randomized blocks, in a 3x5 factorial scheme with four replicates. The NPK rate corresponding to 100% was 120 kg ha-1 respectively for N, P and K. The following variables were evaluated: fruit yield, nutrient accumulation, titratable acidity, soluble solids and ratio between soluble solids and titratable acidity. The concentration of 150% of nutrients was more effective in increasing the yield for the 75/25, 25/75 and 0/100 ratios of mineral and organic fertilizers, and the concentrations of 100 and 150% were the most effective in the accumulation of soluble solids when applied in the mineral and organic fertilizer ratios of 75/25 and 50/50.
The aim of this study was to evaluate the physiological and growth responses of watermelon under application of NPK rates using different proportions of mineral and organic fertilizers. The experiment was taken place in an area located at the Federal University of Campina Grande (UFCG), Campus Pombal - PB (6º48'16'' S and 37º49'15'' W), during the period from June to September 2013. The treatments consisted of three nutrient concentrations of N, P and K (50, 100 and 150% of NPK recommendation for watermelon) and five proportions of mineral and organic fertilizer (100/0, 75/25, 50/50, 25/75 to 0/100). The design was a randomized block in factorial scheme 3 x 5, with four replications. The amount of 100 % was the corresponding NPK 120 kg ha-1, respectively, for N, P and K. They were evaluated: gas exchange, leaf dry matter, stem, fruit and leaf area. The concentration of 150 % of the recommended NPK to the culture of watermelon was the most effective in increasing the physiological characteristics and dry matter accumulation in stem, leaf, fruit, and leaf area. The combined application of mineral and organic fertilizer provides equivalent photosynthetic rate isolated application of mineral fertilizer with an 50/50 ratio the most effective for this variable. The proportions 75/25 and 50/50 were the most efficient in dry matter accumulation in watermelon.
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