RESUMO
Guava is a fruit tree with high potential in the semi-arid region of northeast Brazil. However, qualitative and quantitative water scarcity is a limiting factor for the expansion of irrigated agriculture. Thus, it is necessary to use techniques to mitigate the effects of salt stress, such as foliar application of proline. The objective of this study was to evaluate the effect of foliar application of proline as a mitigator of salt stress effects on the morphophysiology of guava cv. Paluma. The experiment was carried out under field conditions at the 'Rolando Enrique Rivas Castellón' Experimental Farm in São Domingos, PB, Brazil, using a randomized block design in a 5 × 4 factorial scheme referring to five levels of electrical conductivity of irrigation water, ECw (0.8, 1.5, 2.2, 2.9, and 3.5 dS m-1) and four concentrations of proline (0, 8, 16, and 24 mM). Salinity above 0.8 dS m-1 compromised gas exchange, photosynthetic pigment synthesis, photochemical efficiency, and growth of guava plants at 360 days after transplanting. Foliar application of proline at a concentration of 24 mM mitigated the effect of salt stress on the relative water content, stomatal conductance, and carotenoid contents in plants irrigated with 3.6 dS m-1 water. Meanwhile, a proline concentration of up to 18 mM resulted in higher transpiration, CO2 assimilation rate, instantaneous carboxylation efficiency, and absolute growth rate in stem diameter under ECw of 0.8 dS m-1. Proline concentration of up to 24 mM increased the biosynthesis of photosynthetic pigments and the relative growth rate in stem diameter of guava in the period from 190 to 360 days after transplanting.
RESUMO
Cotton is one of the most exploited crops in the world, being one of the most important for the Brazilian Northeast. In this region, the use of irrigation is often necessary to meet the water demand of the crop. Water is often used from underground wells that have a large amount of salt in their constitution, which can compromise the development of crops, so it is vital to adopt strategies that reduce salt stress effects on plants, such as the foliar application of hydrogen peroxide. Thus, the objective of this study was to evaluate the effects of foliar application of hydrogen peroxide on the gas exchange, growth, and production of naturally colored cotton under salt stress in the semi-arid region of Paraíba, Brazil. The experiment was carried out in a randomized block design in a 5 × 5 factorial scheme, with five salinity levels of irrigation water-ECw (0.3, 2.0, 3.7, 5.4 and 7.1 dS m-1)-and five concentrations of hydrogen peroxide-H2O2 (0, 25, 50, 75 and 100 µM), and with three replicates. The naturally colored cotton 'BRS Jade' had its gas exchange, growth, biomass production, and production reduced due to the effects of salt stress, but the plants were able to produce up to the ECw of 3.97 dS m-1. Foliar application of hydrogen peroxide at the estimated concentrations of 56.25 and 37.5 µM reduced the effects of salt stress on the stomatal conductance and CO2 assimilation rate of cotton plants under the estimated ECw levels of 0.73 and 1.58 dS m-1, respectively. In turn, the concentration of 12.5 µM increased water-use efficiency in plants subjected to salinity of 2.43 dS m-1. Absolute and relative growth rates in leaf area increased with foliar application of 100 µM of hydrogen peroxide under ECw of 0.73 and 0.3 dS m-1, respectively. Under conditions of low water salinity (0.3 dS m-1), foliar application of hydrogen peroxide stimulated the biomass formation and production components of cotton.
RESUMO
In the semi-arid region of Northeast Brazil, the combination of irregular rainfall and high evapotranspiration creates a consistent water deficit in plants for most months of the year. This factor prominently limits the vegetable production potential. Consequently, finding effective strategies to alleviate the adverse impacts of water deficit on plants becomes imperative to ensure successful cultivation under irrigated conditions. Within this framework, the objective of this study was to evaluate the influence of nitrogen fertilization on both the morphophysiology and production components of 'Sugar Baby' mini-watermelon plants. The experiment was carried out at the 'Rolando Rivas Castellón' experimental farm in São Domingos, PB, Brazil, within controlled greenhouse conditions. A randomized block design was employed using a 4 × 4 factorial arrangement consisting of four distinct water replenishment levels (50, 75, 100 [control], and 125% of the crop's actual evapotranspiration [ETr]) and four nitrogen application rates (50, 75, 100, and 125% of the recommended rate). Each treatment combination was replicated three times, leading to a total of 48 plants being studied. Gas exchange parameters, content of photosynthetic pigments, relative water content, and electrolyte leakage were assessed. Furthermore, growth metrics, biomass production, production components, and the postharvest quality of 'Sugar Baby' mini-watermelon fruits were also evaluated. Subjecting the plants to deficit irrigation with 50% ETr reduced gas exchange, synthesis of photosynthetic pigments, growth, and fruit quality of 'Sugar Baby' mini-watermelon, irrespective of the nitrogen rate. On the other hand, the irrigation amount of 125% ETr coupled with nitrogen fertilization at 100% of the recommended rate provided higher values of total chlorophyll content, number of leaves, dry mass of root, stem, shoot, and total plant, and the pH value of 'Sugar Baby' mini-watermelon.(AU)
No semiárido do Nordeste do Brasil, a irregularidade de chuvas e elevada evapotranspiração proporcionam déficit hídrico nas plantas na maior parte dos meses do ano, destacando-se como fator limitante para produção de olerícolas. Assim, a identificação de estratégias capazes de amenizar os efeitos do déficit hídrico nas plantas é essencial para produção sob condições irrigadas. Nesse contexto, objetivou-se avaliar o efeito da adubação nitrogenada na morfofisiologia e nos componentes de produção de mini-melancia 'Sugar Baby'. O experimento foi conduzido na Fazenda Experimental 'Rolando Rivas Castellón', São Domingos, Paraíba, sob condições de casa de vegetação, utilizando-se o delineamento de blocos casualizados em esquema fatorial 4 × 4, correspondendo a quatro níveis de reposição hídrica (50, 75, 100 - controle e 125% da evapotranspiração real da cultura - ETr) e quatro doses de nitrogênio - DN (50, 75, 100 e 125% da dose recomendada), com 3 repetições, totalizando 48 plantas. Foram avaliadas as variáveis de trocas gasosas, os teores de pigmentos fotossintéticos, o conteúdo relativo de água e o extravasamento de eletrólitos, o crescimento e a produção de fitomassa, os componentes de produção e a qualidade pós-colheita dos frutos de mini-melancia. A irrigação deficitária com 50% da evapotranspiração real inibiu as trocas gasosas, a síntese de pigmentos fotossintéticos, o crescimento, e a qualidade dos frutos da mini-melancieira 'Sugar Baby', independente da dose de nitrogênio. A lâmina de água com 125% da evapotranspiração real combinada à adubação de 100% da recomendação de nitrogênio proporcionou maiores teores de clorofilas totais, número de folhas e de fitomassa seca das raízes, caule, total, parte aérea e pH dos frutos de mini-melancieira 'Sugar Baby'.(AU)
Assuntos
Citrullus/fisiologia , Fertilizantes/análise , Hidratação , Nitrogênio/análiseRESUMO
Saline water has been used in irrigation due to the limited availability of fresh water, especially in arid and semi-arid regions. However, the use of this type of water can affect crop growth and development. Studies have tested the use of chemical conditioners to minimize the negative effects of salinity on plants. In this scenario, the present study examined the role of hydrogen peroxide in mitigating the negative effects of salt stress on zucchini plants grown in a hydroponic system. The study was carried out in a greenhouse in Pombal - PB, Brazil. The NFT (nutrient film technique) hydroponic system was employed. A randomized complete experimental design was set up with a 4 × 4 factorial arrangement consisting of four levels of electrical conductivity in the nutrient solution (ECns: 2.1 [control], 3.6, 5.1, and 6.6 dS m-1) and four concentrations of hydrogen peroxide (H2O2: 0, 20, 40, and 60 µM), in three replicates. Foliar spraying with H2O2 at 60 and 40 µM associated with the nutrient solution of 2.1 dS m-1 increased stem diameter and root length, respectively, at 47 days after transplanting. However, at ECns higher than 2.1 dS m-1, the application of H2O2 at the concentrations of 60 and 40 µM intensified salt stress, reducing stem diameter and root length. Nutrient solution salinity levels above 2.1 dS m-1 reduce photosynthetic pigments; the number of leaves; leaf area; the length of the main branch; and the dry biomass of stems, leaves, and roots of zucchini plants. Chlorophyll b and carotenoid contents are the variables most sensitive to changes in salinity levels.(AU)
A água salina vem sendo utilizada na irrigação devido à disponibilidade limitada de água doce, principalmente em regiões áridas e semiáridas. No entanto, o uso deste tipo de água pode afetar o crescimento e desenvolvimento das culturas. Alguns estudos têm testado o uso de condicionadores químicos a fim de minimizar os efeitos negativos provocados pela salinidade nas plantas. Nesse contexto, este estudo teve como objetivo avaliar o papel do peróxido de hidrogênio como mitigador dos efeitos negativos do estresse salino em plantas de abobrinha italiana cultivadas em sistema hidropônico. O trabalho foi conduzido em casa de vegetação, em Pombal PB. O sistema de cultivo utilizado foi o hidropônico tipo NFT - Técnica de Fluxo Laminar de Nutriente. O delineamento experimental foi inteiramente casualizados, em esquema fatorial 4 × 4, sendo quatro níveis de condutividade elétrica da solução nutritiva - CEsn (2,1 (controle); 3,6; 5,1 e 6,6 dS m-1), e quatro concentrações de peróxido de hidrogênio H2O2 (0; 20; 40 e 60 µM), com 3 repetições. A pulverização foliar de H2O2 na concentração de 60 e 40 µM associada a solução nutritiva com condutividade elétrica de 2,1 dS m-1 promoveu aumento no diâmetro do caule e comprimento da raiz, respectivamente, aos 47 dias após o transplantio. Contudo, em soluções nutritivas com condutividade elétrica superior a 2,1 dS m-1 a aplicação de H2O2 em concentrações de 60 e 40 µM intensificou o efeito do estresse salino, reduzindo o diâmetro de caule e o comprimento das raízes, respectivamente. A salinidade da solução nutritiva acima de 2,1 dS m-1 reduziu os pigmentos fotossintéticos, o número de folhas, área foliar, o comprimento do ramo principal, fitomassa seca do caule, de folhas e de raiz da abobrinha italiana, sendo os teores de clorofila b e carotenoides as variáveis mais sensíveis.(AU)