High nighttime temperatures impair rice yield. Additionally, heat stress periods have increased during the last years in the rice areas of the tropics. The aim of this study was to physiologically characterize six genotypes of rice (a commercial cultivar (ʻF60ʼ) and five selected lines (ʻIR 1561ʼ, ʻFLO 2764ʼ, ʻLV447-1ʼ, ʻCT19021ʼ, and ʻLV1401ʼ) subjected to two nighttime temperatures (24 and 30 °C), based on different physiological traits. When the collar formed on leaf 6 of the main stem, one group of six plants in each genotype was subjected to 30 °C from 18:00 to 24:00 hours for eight days, while the other group remained at 24 °C. Differences were found in the interaction between genotype and nighttime temperatures, where a high night temperature reduced leaf photosynthesis by approximately 50% in all genotypes compared to the controls (20 µmol vs. 10 µmol CO 2 m -2 s -1 , respectively). In general, higher plant respiration was also observed in almost all genotypes when the plants were exposed to 30 °C. However, rice plants of the genotype ʻF60ʼ showed a constant respiration under two different night temperatures. A high nighttime temperature increased the electrolyte leakage and malondialdehyde content only in the ʻLV1401ʼ plants. Plant growth and F v /F m ratio were separately conditioned by the night temperature or the genotype factor. A lower total plant dry weight was found at 30 °C (620.36 mg) than in rice plants exposed to 24 °C (254.16 mg). The F v /F m ratio was slightly diminished at a high nighttime temperature. These results suggest that physiological variables, such as leaf photosynthesis, plant respiration, malondialdehyde content and leaf photosynthetic pigments, can be considered markers for characterizing tolerant genotypes in earlier growth phases during plant breeding programs.
Titulo en ingles: Water stress on citric fruit (Citrus spp.): a reviewTitulo en portugues: O estresse hídrico em cítricos (Citrus spp): Uma revisãoResumen: Los cítricos constituyen el principal producto frutícola a nivel mundial por sus ventajas y beneficios Una humedad adecuada y homogénea en el suelo garantiza su calidad y producción, incluso en los países subtropicales donde existen distribuciones uniformes de la precipitación La mayoría de las áreas de cítricos cuentan con infraestructura de riego localizado, lo que incrementa la eficiencia en el uso del agua Sin embargo, la presión sobre los recursos hídricos hace necesario seguir estudiando el comportamiento ante condiciones adversas para manejar eficientemente la programación del riego En este artículo se presenta el efecto del déficit hídrico en los cítricos Además de algunas respuestas fisiológicas y anatómicas que manifiestan los cítricos a este déficit y que efecto tiene un estrés hídrico sobre la producción y el crecimiento vegetativo Por último se recopilan algunos resultados de la aplicación de riego deficitario como una forma de ahorrar agua sin afectar la producciónPalabras clave: agua, evapotranspiración, árboles frutales, riego deficitario, estrés hídricoAbstract: Citric fruit represent the main fruit product worldwide due to their advantages and benefits Adequate and homogenous moisture in the soil ensures consistent fruit quality and production, even in subtropical countries having patterns Most citricrowing areas have drip irrigation infrastructure, thereby increasing wateruse efficiency However, pressure on water resources means that water use in adverse conditions must continue to be studied to ensure efficient irrigation scheduling This paper deals with the effect of water stress on citric plants, as well as some of their physiological and anatomical responses to such deficit and what effect hydric stress has on vegetable production and growth Some results are compiled regarding deficit irrigation (DI) as a way to save water without affecting production.Key words: water, evapotranspiration, fruit tree, deficit irrigation, water stressResumo: Os cítricos constituem o principal produto frutícola no mundo pelas suas vantagens e benefícios Uma umidade adequada e homogênea no solo garante sua qualidade e produção, ainda nos países subtropicais onde existe distribuição uniforme da precipitação A maioria das áreas citrícolas, contam com infraestrutura de risco localizado, o que incrementa a eficiência no uso da água Porém, a pressão sobre os recursos hídricos faz necessário estudar o comportamento em condições adversas para manejar eficientemente o planejamento da irrigação Nesta revisão apresenta-se o efeito do déficit hídrico nos cítricos Além disto, algumas respostas fisiológicas e anatômicas pelos cítricos ao déficit e o efeito do estresse hídrico sobre a produção e o crescimento vegetativo Finalmente, apresentam-se alguns resultados da aplicação de irrigação deficitária, como forma de poupar água sem afetar a produção.Palavras chave: agua, evapotranspiração, arvores frutais, irrigação deficitária, estresse hídrico
Debido al sistema radicular superficial, la cebolla de bulbo requiere de un suministro de riego en el momento y con la intensidad adecuada para favorecer la absorción de agua y nutrientes y obtener altos rendimientos. Se evaluó el efecto de diferentes láminas de riego en el crecimiento y desarrollo de cebolla de bulbo en un suelo franco arenoso y con un sistema de riego por aspersión. Se usó un diseño experimental completamente al azar con cuatro tratamientos (coeficientes de cultivo de 0,8; 1,0; 1,2 y 1,4 de la evaporación (Ev)), cada uno con 16 repeticiones, para un total de 64 unidades experimentales, donde cada unidad experimental correspondió a una parcela de 1 m2. El coeficiente de 1,2 (43 L por planta por ciclo) presentó los mayores promedios en masa seca total y masa seca del bulbo con diferencias significativas en relación al coeficiente de 0,8, pero sin diferencias con la aplicación de 1,0 y 1,4 de la Ev. Además, en masa seca de raíz el tratamiento de 1,2 Ev presentó el mayor promedio. En el crecimiento general no hubo diferencias significativas los primeros 70 días después del trasplante, pero luego de este tiempo se presentaron diferencias estadísticas y la aplicación de 1,2 de la Ev presentó la mayor acumulación de masa seca.
Spinach is susceptible to drought conditions, and, because of climate change, it is necessary to optimize water application to crops. Therefore, a test was carried out in a completely randomized design (CRD) with four treatments consisting of the following irrigation suspension durations: T1: 0 d, T2: 4 d, T3: 7 d and T4: 10, with six replicates for a total of 24 experiment units (EU). Each EU consisted of 6 plants, for a total of 120 plants that were transplanted to 2 L pots with a mixture of peat and soil (2:1). The upper part of the substrate was maintained with a higher moisture content in the treatment without irrigation suspension and in the one with irrigation suspended for 4 d. An inversely proportional relationship was observed between the moisture content and the leaf water potential. The treatment without irrigation suspension recorded the highest leaf water potential value during the measurement period. There were no significant differences between the chlorophyll content in the SPAD units or for the leaf area, stomatal conductance and dry mass. The fresh mass presented significant differences and had the highest value in the treatment without suspension of irrigation.
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