Eco-physiological behavior of tamarind (Tamarindus indica L.) in dry environment of West Africa (case study of Senegal).

Water deficit is considered by several authors to be the most limiting factor for agricultural production in the subtropics (Kizito et al., 2006; Porcel and Ruiz-Lozano, 2004; Bader et al., 2006; Logan et al., 2010; Rodriguez-Gamir et al., 2011; Conedera et al., 2011). On woody plants, only a few isolated studies (on Acacia, and combretaceae) exist in the tropical zone south of the Sahara. Noteworthy are the works done on Sahelian forest species, Acacia tortilis (Diouf, 1996), Combretum glutinosum, Guiera senegalensis; Piliostigma reticulatum; Balanites aegyptica, Boscia senegalensis, A. senegal and Ziziphus mauritiana (Fournier, 1995; Kizito et al., 2006; Lufafa et al., 2008). Characterization of plant water functioning is a tool for selecting plants and/or varieties for their tolerance to water deficit (Lufafa et al., 2008; Zhu Qiuan et al., 2011; Logan et al., 2010). It is most often done at young age for ease of use (nursery and early field establishment of seedlings). However, even as adults, woody plants remain dependent on climatic factors such as rainfall (Kisito et al., 2007; Lufafa et al., 2008). It is therefore important to understand the in situ water functioning of adult plants to better explain the depressive effects of such complex water stress at a young age. However, the behavior of plants in situ is influenced by the climatic conditions and the uniformity (age) of the subjects (tamarind plants) to be followed. The present work was carried out on adult T. indica plants in situ in Senegal (Niokhoul in the Sahelian zone and Mbassis in the Sudano-Sahelian zone) and aimed mainly to: (1) understand and describe the physiological water management strategies of tamarind under arid conditions; and (2) understand the impact of this water management strategy on phenology and productivity. The study was conducted in Senegal, characterized by a dry and arid climate. It adopted a field approach (Seghieri, 2010; Conedera et al., 2010) based on adult stands and climatic data collected at the study sites. Ultimately, the adaptation mechanism of tamarind to water deficit would be that of avoidance, described by various authors (Khalfaoui, 1985; Lacape, 1996; Nwalozie and Annerose, 1996; Rouhi et al., 2007; Roussel, 2008; Maes et al., 2009). Indeed, the plant first proceeds to a decrease in water potential (case of the Mbassis stand) and in case of continuous water deficit, it integrates the reduction of the leaf surface by the progressive fall of the leaves and flowers which can go up to the total defoliation (case of the stand of the Sahelian zone in Niokhoul).

Osmoprotection in Salvia hispanica L seeds under water stress attenuators / Osmoproteção em sementes de Salvia hispanica L sob atenuadores do estresse hídrico

Salvia hispanica cultivation is recent in Brazil and occurs in the off-season, when there is lower water availability in the soil. Water deficit is one of the abiotic factors that most limit germination for compromising the sequence of metabolic events that culminate with seedling emergence. Several attenuating substances have been used to mitigate the effects resulting from this stress and give higher tolerance to the species. Thus, the objective of this study was to evaluate the action of different agents as water stress attenuators in the germination and accumulation of organic compounds in S. hispanica seedlings. The treatments consisted of pre-soaking the seeds for 4 hours in salicylic acid (1 mM.L-¹), gibberellic acid (0.4 mM.L-¹), distilled water and control treatment (without soaking). The seeds were germinated at osmotic potentials of 0.0, -0.1, -0.2, -0.3 and -0.4 MPa, using PEG 6000 as an osmotic agent. The variables germination percentage, germination speed index, shoot and primary root lengths, total dry mass, proline, total soluble sugars and total free amino acids were analyzed. Salicylic acid and gibberellic acid led to the best results among the attenuators tested, increasing germination, length, dry mass and biochemical components of S. hispanica seedlings under water deficit. Therefore, salicylic and gibberellic acids are efficient in mitigating water stress in S. hispanica seeds up to the potential of -0.4 MPa.

O cultivo da Salvia hispanica é recente no Brasil e se dá no período de entressafra, quando há menor disponibilidade hídrica no solo. O déficit hídrico é um dos fatores abióticos que mais limitam a germinação por comprometer a sequência de eventos metabólicos que culminam com a emergência da plântula. Diversas substâncias atenuadoras têm sido empregadas com a finalidade de mitigar os efeitos resultantes desse estresse e conferir maior tolerância às espécies. Desse modo, objetivou-se avaliar a ação de diferentes agentes como atenuadores do estresse hídrico na germinação e acúmulo de compostos orgânicos em plântulas de S. hispanica. Os tratamentos consistiram na pré-embebição das sementes durante 4 horas em ácido salicílico (1 mM.L-¹), ácido giberélico (0,4 mM.L-¹), água destilada e o tratamento controle (sem embebição). As sementes foram germinadas sob os potenciais osmóticos 0,0, -0,1, -0,2, -0,3 e -0,4 MPa, utilizando PEG 6000 como agente osmótico. Analisaram-se as variáveis porcentagem de germinação, índice de velocidade de germinação, comprimento da parte aérea e da raiz primária, massa seca total, prolina, açúcares solúveis totais e aminoácidos livres totais. O ácido salicílico e o ácido giberélico apresentaram os melhores resultados, dentre os atenuadores testados, incrementando a germinação, o comprimento, a massa seca e os componentes bioquímicos de plântulas de S. hispanica sob déficit hídrico. Logo, os ácidos salicílico e giberélico são eficientes na mitigação do estresse hídrico em sementes de S. hispanica até o potencial -0,4 MPa.

Osmoprotection in Salvia hispanica L. seeds under water stress attenuators

Abstract Salvia hispanica cultivation is recent in Brazil and occurs in the off-season, when there is lower water availability in the soil. Water deficit is one of the abiotic factors that most limit germination for compromising the sequence of metabolic events that culminate with seedling emergence. Several attenuating substances have been used to mitigate the effects resulting from this stress and give higher tolerance to the species. Thus, the objective of this study was to evaluate the action of different agents as water stress attenuators in the germination and accumulation of organic compounds in S. hispanica seedlings. The treatments consisted of pre-soaking the seeds for 4 hours in salicylic acid (1 mM.L-1), gibberellic acid (0.4 mM.L-1), distilled water and control treatment (without soaking). The seeds were germinated at osmotic potentials of 0.0, -0.1, -0.2, -0.3 and -0.4 MPa, using PEG 6000 as an osmotic agent. The variables germination percentage, germination speed index, shoot and primary root lengths, total dry mass, proline, total soluble sugars and total free amino acids were analyzed. Salicylic acid and gibberellic acid led to the best results among the attenuators tested, increasing germination, length, dry mass and biochemical components of S. hispanica seedlings under water deficit. Therefore, salicylic and gibberellic acids are efficient in mitigating water stress in S. hispanica seeds up to the potential of -0.4 MPa.

Resumo O cultivo da Salvia hispanica é recente no Brasil e se dá no período de entressafra, quando há menor disponibilidade hídrica no solo. O déficit hídrico é um dos fatores abióticos que mais limitam a germinação por comprometer a sequência de eventos metabólicos que culminam com a emergência da plântula. Diversas substâncias atenuadoras têm sido empregadas com a finalidade de mitigar os efeitos resultantes desse estresse e conferir maior tolerância às espécies. Desse modo, objetivou-se avaliar a ação de diferentes agentes como atenuadores do estresse hídrico na germinação e acúmulo de compostos orgânicos em plântulas de S. hispanica. Os tratamentos consistiram na pré-embebição das sementes durante 4 horas em ácido salicílico (1 mM.L-1), ácido giberélico (0,4 mM.L-1), água destilada e o tratamento controle (sem embebição). As sementes foram germinadas sob os potenciais osmóticos 0,0, -0,1, -0,2, -0,3 e -0,4 MPa, utilizando PEG 6000 como agente osmótico. Analisaram-se as variáveis porcentagem de germinação, índice de velocidade de germinação, comprimento da parte aérea e da raiz primária, massa seca total, prolina, açúcares solúveis totais e aminoácidos livres totais. O ácido salicílico e o ácido giberélico apresentaram os melhores resultados, dentre os atenuadores testados, incrementando a germinação, o comprimento, a massa seca e os componentes bioquímicos de plântulas de S. hispanica sob déficit hídrico. Logo, os ácidos salicílico e giberélico são eficientes na mitigação do estresse hídrico em sementes de S. hispanica até o potencial -0,4 MPa.

Osmoprotection in Salvia hispanica L. seeds under water stress attenuators / Osmoproteção em sementes de Salvia hispanica L. sob atenuadores do estresse hídrico

Salvia hispanica cultivation is recent in Brazil and occurs in the off-season, when there is lower water availability in the soil. Water deficit is one of the abiotic factors that most limit germination for compromising the sequence of metabolic events that culminate with seedling emergence. Several attenuating substances have been used to mitigate the effects resulting from this stress and give higher tolerance to the species. Thus, the objective of this study was to evaluate the action of different agents as water stress attenuators in the germination and accumulation of organic compounds in S. hispanica seedlings. The treatments consisted of pre-soaking the seeds for 4 hours in salicylic acid (1 mM.L-1), gibberellic acid (0.4 mM.L-1), distilled water and control treatment (without soaking). The seeds were germinated at osmotic potentials of 0.0, -0.1, -0.2, -0.3 and -0.4 MPa, using PEG 6000 as an osmotic agent. The variables germination percentage, germination speed index, shoot and primary root lengths, total dry mass, proline, total soluble sugars and total free amino acids were analyzed. Salicylic acid and gibberellic acid led to the best results among the attenuators tested, increasing germination, length, dry mass and biochemical components of S. hispanica seedlings under water deficit. Therefore, salicylic and gibberellic acids are efficient in mitigating water stress in S. hispanica seeds up to the potential of -0.4 MPa.

O cultivo da Salvia hispanica é recente no Brasil e se dá no período de entressafra, quando há menor disponibilidade hídrica no solo. O déficit hídrico é um dos fatores abióticos que mais limitam a germinação por comprometer a sequência de eventos metabólicos que culminam com a emergência da plântula. Diversas substâncias atenuadoras têm sido empregadas com a finalidade de mitigar os efeitos resultantes desse estresse e conferir maior tolerância às espécies. Desse modo, objetivou-se avaliar a ação de diferentes agentes como atenuadores do estresse hídrico na germinação e acúmulo de compostos orgânicos em plântulas de S. hispanica. Os tratamentos consistiram na pré-embebição das sementes durante 4 horas em ácido salicílico (1 mM.L-1), ácido giberélico (0,4 mM.L-1), água destilada e o tratamento controle (sem embebição). As sementes foram germinadas sob os potenciais osmóticos 0,0, -0,1, -0,2, -0,3 e -0,4 MPa, utilizando PEG 6000 como agente osmótico. Analisaram-se as variáveis porcentagem de germinação, índice de velocidade de germinação, comprimento da parte aérea e da raiz primária, massa seca total, prolina, açúcares solúveis totais e aminoácidos livres totais. O ácido salicílico e o ácido giberélico apresentaram os melhores resultados, dentre os atenuadores testados, incrementando a germinação, o comprimento, a massa seca e os componentes bioquímicos de plântulas de S. hispanica sob déficit hídrico. Logo, os ácidos salicílico e giberélico são eficientes na mitigação do estresse hídrico em sementes de S. hispanica até o potencial -0,4 MPa.

Limited evidence of coupling between above and belowground functional traits in tropical dry forest seedlings / Evidencia limitada de acoplamiento entre rasgos funcionales por encima y por debajo del suelo en plántulas de bosque seco tropical

Abstract Introduction: Water availability is one of the main factors determining the distribution of woody species in the tropics. Although the functional mechanisms that determine the species tolerance to water deficit have been extensively studied in adult individuals, the responses of early ontogenetic stages have been less explored. Objective: To identify functional strategies and trait correlations between different seedlings' dimensions (leaf, stem, and root). We expect limited coordination between above and below-ground functional traits due to a single conservation-acquisition trade-off cannot capture the variability of functions and environmental pressures to which the root system is subjected. Methods: We measured 12 functional traits belonging to 38 seedling species in a tropical dry forest in Colombia. We explored the relationships between pairs of traits using Pearson correlations, and to obtain an integrated view of the functional traits, a principal component analysis (PCA) was performed. Results: The results showed limited evidence of linkage between above- and below-ground traits, but we did find significant correlations between traits for the continuum of conservative and acquisitive strategies. Root traits related to water and nutrient take capacity formed an orthogonal axis to the acquisitive-conservative continuum. Conclusions: Our results showed that dry forest seedlings have different functional strategies to cope with water deficit. The incorporation of root traits helps to explain new functional strategies not reported for leaf and stem traits. This study contributes to understanding the mechanisms that explain species coexistence and is particularly relevant for predicting future forest trajectories.

Resumen Introducción: La disponibilidad de agua es uno de los principales factores que determina la distribución de las especies leñosas en los trópicos. A pesar que los mecanismos funcionales que determinan la tolerancia de las especies al déficit hídrico han sido ampliamente estudiados en los individuos adultos, las respuestas de estados ontogenéticos tempranos han sido menos exploradas. Objetivo: Identificar las estrategias funcionales y las correlaciones de rasgos entre diferentes dimensiones de las plántulas (hoja, tallo y raíz). Nosotros esperamos baja coordinación entre los rasgos funcionales sobre y bajo el suelo debido a que un único trade-off conservación-adquisición de recursos, no puede capturar la variabilidad de funciones y presiones ambientales a las que están expuestas las raíces. Métodos: Medimos 12 rasgos funcionales pertenecientes a 38 plántulas en un bosque seco en Colombia. Exploramos las relaciones entre pares de rasgos usando correlaciones de Pearson, y para tener una visión integrada de los rasgos funcionales, usamos un análisis de componentes principales (ACP). Resultados: Reportamos limitada evidencia de acoplamiento entre los rasgos sobre y bajo el suelo, pero encontramos correlaciones significativas entre el continuo de estrategias conservativas y adquisitivas. Los rasgos de raíz relacionados con la capacidad de absorción de agua y nutrientes formaron un eje ortogonal al continuo adquisitivo-conservativo. Conclusiones: Nuestros resultados mostraron que las plántulas del bosque seco tienen diferentes estrategias funcionales para lidiar con el déficit hídrico. La incorporación de los rasgos de la raíz ayuda a explicar nuevas estrategias funcionales no reportadas por los rasgos de hoja y tallo. Este estudio contribuye al entendimiento de los mecanismos que explican la coexistencia de especies y es particularmente relevante para predecir las trayectorias de los bosques futuros.

Organic fertilization as an alternative to the chemical in cherry tomato growing under irrigation depths

Two experiments were carried out to evaluate the effects of organic fertilization as an alternative to the chemical on the yield and quality of cherry tomato grown under different irrigation depths in protected environment, in 2013 and 2014. The experimental design was in randomized blocks (5 x 3 factor), with five irrigation depths as the factors (70%, 85%, 100%, 115% and 130% of ETc) and three types of fertilization: no fertilized soil (control), NPK fertilized soil (Chemical) and earthworm humus fertilized soil (organic). The following were evaluated in this study: water use efficiency, number of aborted flowers, total soluble solid content, transverse and longitudinal diameter of the fruits, number of fruits and fruit yield per plant. Organic fertilization is an alternative to the chemical with no losses in yield and fruit quality. The increase in water depth enhanced yield and fruit diameters and reduced water use efficiency. Water use efficiency was more sensitive to the increments in water depth than to different types of fertilization. The values ​​of °Brix obtained in the experiment were classified as acceptable for the domestic and international market when submitted to organic fertilization.

Seed discontinuous hydration does not benefit germination, but improves drought tolerance of Triplaris gardneriana seedlings

The discontinuous seed hydration enables the acquisition of tolerance to environmental stresses, causing a stress imprint. It may modify metabolic patterns and lead to improved stress responses. This study aims to evaluate the effects of discontinuous hydration on germination and on seedling growth of Triplaris gardneriana Wedd. under intermittent drought. The seeds have gone through cycles (0, 1, 2 and 3) of hydration and dehydration (HD). The seedlings produced were subjected to water deficit (daily watering and intervals of seven and fourteen days between watering). Seed germinability parameters and, relative growth rate (RGR) of seedling, leaf area, dry matter yield and leaf relative water content (RWC) were evaluated. The HD cycles did not benefit germination, but two HD cycles induced a better biomass accumulation and increased leaf area in seedlings under moderate water deficit, while three HD cycles promoted an increase in RGR and influenced the RWC values. Severe stress affects seedling growth, but subjection to HD cycles minimizes the deleterious effects of drought, suggesting discontinuous hydration acts leading stress imprint in plants.

Gas Exchange, Root Morphology and Nutrients in Maize Plants Inoculated with Azospirillum brasilense Cultivated Under Two Water Conditions

HIGHLIGHTS Azospirillum brasilense stimulates root growth in maize under water deficit. Maize inoculated with A. brasilense shows greater photosynthesis under drought conditions. Under water deficit, maize plants inoculated with A. brasilense showed greater water use efficiency (WUE).

Abstract The objective of this study was to evaluate the gas exchange, root morphology and nutrient concentration in maize plants inoculated with A. brasilense under two water conditions. The experiments were carried out in a greenhouse, one under irrigation and the other under water deficit. The treatments consisted of four A. brasilense inoculants (control (without inoculation), Az1 (CMS 7 + 26), Az2 (CMS 11 + 26) and Az3 (CMS 26 +42). At the V6 plant stage, water stress was imposed on maize plants for 15 days. The phytotechnical characteristics, gas exchange, root morphology, root dry matter and macronutrient analysis were evaluated after 15 days of water deficit imposition. The water deficit caused a reduction in the development of maize plants. The presence of A. brasilense Az1 under the same condition yielded higher photosynthesis, carboxylation efficiency, water use efficiency, and greater soil exploration with increased length, surface area and root volume of plants. Inoculation by A. brasilense increased root system volume by an average of 40 and 47% under irrigation and water deficit, respectively, when compared to non-inoculated plants. The inoculant Az1 attenuated the deleterious effects caused by drought and yielded the best growth of the root system, resulting in the tolerance of maize plants to water deficit.

Efecto de la interacción luz-agua sobre la fotosíntesis de la Vanilla planifolia (Orchidaceae) / Light-water interaction effect on photosynthesis of the Vanilla planifolia (Orchidaceae)

Introducción: La vainilla (Vanilla planifolia Andrews) es una planta CAM de gran importancia económica en el mercado mundial de saborizantes y aromatizantes. Por ser una planta hemiepífita que inicialmente crece en el sotobosque sombreado y posteriormente asciende hasta el dosel, se aclimata a diferentes condiciones de radiación y humedad. La posibilidad de extender su cultivo a zonas secas donde sea menor la incidencia de enfermedades, dependerá de su respuesta a períodos prolongados de sequía. Objetivo: Evaluar los efectos de la interacción entre la radiación y la humedad sobre los parámetros de la fotosíntesis y funcionamiento del CAM de plantas de vainilla en sus fases iniciales de desarrollo vegetativo, y determinar si las condiciones de radiación en las que crece la planta pueden ayudar a moderar los efectos negativos de la sequía. Métodos: Se evaluaron plantas de vainilla que crecieron con riego durante 18 meses en casetas con iluminación relativa (IR) de 8, 17, 31 y 67 %; posteriormente se suspendió el riego y se fueron deshidratando durante 94 días hasta alcanzar un contenido de humedad crítico (contenido hídrico relativo, CHR ≤ 50 %), y finalmente se reinició el riego durante 22 días; se evaluó el efecto de estos procesos sobre la asimilación de CO2, la acidez titulable y la eficiencia cuántica del Fotosistema II (Fv/Fm). Resultados: Bajo condiciones intermedias de IR (17 % y 31 %), la asimilación de CO2 y laacumulación nocturna de ácidos orgánicos presentaron la menor afectación por el déficit hídrico, así como la mejor recuperación luego de la rehidratación. El CHR se vio más afectado por la disponibilidad de agua en el tejido vegetal, mientras que Fv/Fm lo fue por el ambiente de radiación. Los efectos combinados de estrés hídrico y alta radiación ocasionaron daños irreversibles en la fotosíntesis para el tratamiento de IR de 67 %. Conclusiones: En las plantas de vainilla, el impacto negativo de la sequía sobre los parámetros de la fotosíntesis fue mayor en alta radiación; sin embargo, en condiciones de baja radiación también aumentó la susceptibilidad de las plantas a la sequía, en comparación con los ambientes de radiación intermedia, en los cuales la densidad de flujo de fotones media fue de 340 μmol m-2 seg-1 (17 % de IR) y 620 μmol m-2 seg-1 (31 % de IR). Estos resultados sugieren el potencial de cultivar vainilla en zonas con sequía estacional bajo sistemas productivos de baja tecnificación, manteniendo estas condiciones de radiación.

Introduction: Vanilla planifolia Andrews is a CAM plant of economic importance in the global market of flavorings and essences. Being a hemiepiphyte which initially grows in the shady understory and later climbs to the canopy, it acclimates to different conditions of radiation and humidity. The possibility of extending this crop to dry areas where the incidence of diseases is lower will depend on the response to prolonged periods of drought. Objective: To evaluate the effects of the interaction of radiation and humidity on the parameters of photosynthesis and operation of CAM of vanilla plants, and to determine if the radiation environment could help to moderate the negative effects of drought. Methods: We evaluated well-watered vanilla plants grown for 18 months in relative illumination (RI) of 8, 17, 31 and 67 %, which underwent dehydration for 94 days until reaching critical water content (relative water content, RWC < 50 %) and then rehydration for 22 days; variables evaluated were: CO2 assimilation, titratable acidity, and quantum efficiency of Photosystem II (Fv / Fm). Results: Under intermediate conditions of radiation (17 % and 31 % RI), CO2 assimilation and nocturnal accumulation of organic acids were less affected by water deficit and also showed the best recovery after rehydration. The RWC was most affected by the water available in plant tissue, while Fv / Fm was affected by radiation. The combined effects of water stress and high radiation caused irreversible damage to photosynthesis for the 67 % RI treatment. Conclusions: In vanilla plants, the negative impact of drought on photosynthetic parameters was greater in high radiation; however, in low radiation conditions the susceptibility of plants to drought also increased, as compared to intermediate radiation environments, which were under a mean photon flux density of 340 µmol m-2 s-1 (17 % IR) and 620 µmol m-2 s-1 (31 % IR). These results suggest the potential for growing vanilla in areas with seasonal drought under low-tech production systems, maintaining these radiation conditions.

Permanent wilt point from two methods for different combinations of citrus rootstock / Ponto de murcha permanete a partir de dois métodos para diferentes combinações copa porta-enxerto de citros

ABSTRACT: Considering that water is extremely important in agricultural production, but with restricted availability in some Brazilian regions, this research sought to identify the water limit for the rootstocks: Cleóptra tangerine (Citrus reshni hort. Ex Tan), Volkamer lime (Citrus Volkameriano Pasquale), Citrandarin 'indio' (TSK X TRENG 256), Santa Cruz Rangpur lime (Citrus × limonia) and Sunki Tropical tangerine (Citrus sunki HORT. EX TAN) grafted orange 'Pera' (Citrus sinensis), obtained by two methods: the traditional method of determining the permanent wilting point described by SHANTZ & BRIGGS (1912) recovery of plants with saturated environment and by irrigating recovery method. The experimental design used was in a completely randomized design with four replications totaling 20 experimental plots. It was verified that the rootstocks Cravo Santa Cruz lemon and Volkamerian lemon were the most resistant in initial conditions of water restriction, evaluated by the method of BRIGGS & SHANTZ (1912), with recording of humidity of 0.0488 and 0.0489 respectively. Under more severe conditions of water restriction, determined by the irrigation method, Volkamerian lemon presented the highest resistance, with a humidity of 0.0371.

RESUMO: Considerando que a água é extremamente importante na produção agrícola, mas com restrita disponibilidade em algumas regiões brasileiras, é que esse trabalho buscou identificar o limite hídrico inferior para os porta-enxertos: tangerina Cleóptra (Citrus reshni hort. Ex Tan), limão Volkameriano (Citrus Volkameriano Pasquale), citrandarin 'Indio' -TSK X TRENG 256, limão Cravo Santa Cruz (Citrus × limonia) e tangerina Sunki Tropical (Citrus sunki HORT. EX TAN) enxertadas em laranja 'Pêra' (Citrus sinensis), obtidos por dois métodos: o método tradicional de determinação do ponto de murchamento permanente descrito por BRIGGS & SHANTZ (1912) com recuperação das plantas em ambiente saturado e o método de recuperação por rega. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições, totalizando 20 parcelas experimentais. Verificou-se que os porta-enxertos limão Cravo Santa Cruz e o limão Volkameriano foram os mais resistentes em condições iniciais de restrição hídrica, avaliado pelo método de BRIGGS & SHANTZ (1912), com registro das umidades de 0,0488 e 0,0489, respectivamente. Em condições mais severas de restrição hídrica, determinado pelo método de rega, o limão Volkameriano foi o que apresentou maior resistência, com a umidade de 0,0371.

Morphological and physiological variation in Toona ciliata under water and salinity stress / Variação morfológica e fisiológica em Toona ciliata sob efeito de estresse hídrico e salino

ABSTRACT: The objective of this paper was to test the effects of water deficit, saturation and salinity in individuals of Toona ciliata. Seven treatments were tested: the control group, the complete suspension of irrigation, the permanent saturation of the pot soil and four doses of NaCl (50, 100, 200 and 400 µmol). The experimental design was completely randomized, with 8 repetitions in each treatment. Physiologic evaluations were carried out during the experiment, and morphologic evaluations at the end. The plants were responsive to the applied stresses comparatively to the control group. Reductions were observed in morphological and physiological variables in all treatments under stress. All individuals under stress recovered slightly in the end of the experiment, and began to sprout again, representing a probable adaptation to the conditions.

RESUMO: O trabalho teve como objetivo mensurar os efeitos de déficit hídrico, saturação e efeito da salinidade em mudas de Toona ciliata. Foram testados sete tratamentos: controle, suspensão completa de irrigação, saturação permanente do solo no vaso e quatro diferentes doses de NaCl (50, 100, 200 e 400 µmol). O delineamento experimental utilizado foi inteiramente casualizado, com oito repetições. Foram realizadas avaliações fisiológicas ao longo do experimento e ao final, avaliações morfológicas. As plantas foram responsivas aos estresses aplicados comparativamente ao controle. Havendo redução em variáveis morfológicas e fisiológicas em todos os tratamentos sobre estresse. Todos os indivíduos sob estresse tiveram uma pequena recuperação ao final do experimento, iniciando a rebrotar, representando uma possível adaptação ao estresse.

Análisis regional de zonas homogéneas de precipitación en Carabobo, Venezuela / Regional analysis of homogeneous precipitation areas in Carabobo, Venezuela / Análise regional de áreas de precipitação homogênea em Carabobo, Venezuela

Resumen Introducción. La utilidad primordial de los datos sobre el clima para planificar el desarrollo sostenible en áreas agrícolas y hacer frente a todas las consecuencias del cambio climático ya ha quedado firmemente establecida en diferentes programas y políticas a nivel mundial. Objetivo. Analizar la variabilidad espacio temporal de la precipitación e identificar las zonas homogéneas a partir de datos mensuales y anuales (1969-1999) provenientes de las estaciones climatológicas en Carabobo, Venezuela. Materiales y métodos. Para definir subgrupos de estaciones pluviométricas que caractericen zonas homogéneas se aplicaron técnicas multivariadas (análisis de componentes principales y análisis de conglomerados) basadas en la similitud del comportamiento de las series de datos de lluvia anual precipitada. Finalmente se elaboró el mapa de distribución espacial de la precipitación mediante la interpolación kriging. Resultados. Se lograron identificar cuatro grupos de estaciones con comportamiento similar en lo que se refiere a los procesos pluviométricos. Esta investigación permitió conocer el comportamiento espacial y temporal de la precipitación, caracterizada por la marcada estacionalidad producto de la influencia directa de la Zona de Convergencia Intertropical. La tendencia mostró un patrón de distribución espacial con una gradación que va de menor a mayor en sentido noreste a sureste. Conclusiones. Este estudio permitió estimar la regularidad espacial del comportamiento de la lluvia y del grado de heterogeneidad de este elemento climático año tras año, que a su vez representa el inicio de la planificación estratégica a nivel regional.

Abstract Introduction: The primary utility of climate data for planning sustainable development in agricultural areas and addressing all the consequences of climate change has already been firmly established in different programs and policies worldwide. Objective: Analyze the temporal space variability of precipitation and identify homogeneous areas based on monthly and annual data from weather stations in Carabobo, Venezuela, during the period 1969-1999. Materials and methods: To define subgroups of rainfall stations that characterize homogeneous zones, multivariate techniques (principal component analysis and cluster analysis) were applied based on the similarity of the behavior of the data series of precipitated annual rainfall. Finally, the spatial distribution map of the precipitation was prepared by means of kriging interpolation. Results: It was possible to identify four groups of stations with similar behavior in terms of rainfall processes. This investigation allowed to know the spatial and temporal behavior of precipitation, characterized by the marked seasonality resulting from the direct influence of the Intertropical Convergence Zone. The trend showed a pattern of spatial distribution with a gradation that goes from minor to major in the northeast to southeast direction. Conclusion: In addition, this study allowed estimating the spatial regularity of rainfall behavior and the degree of heterogeneity of this climatic element year after year, which in turn represents the beginning of strategic planning at the regional level.

Resumo Introdução. A utilidade primordial dos dados climáticos para planejar o desenvolvimento sustentável em áreas agrícolas e abordar todas as consequências da alteração climática já ficou firmemente estabelecida nos diferentes programas e políticas ao nível mundial. Objetivo. Analisar a variabilidade do espaço temporal da precipitação e identificar as zonas homogêneas a partir de dados mensais e anais (1969-1999) provenientes das estações climatológicas em Carabobo, Venezuela. Materiais e métodos. Para definir subgrupos de estações pluviométricas que posam caracterizar as zonas homogêneas aplicaram-se técnicas multivariadas (análise de componentes principais e análise de conglomerados) baseadas na similitude do comportamento das series de dados de chuva anual precipitada. Finalmente elaborou-se o mapa de distribuição espacial da precipitação mediante a interpolação kriging. Resultados. Conseguiu-se identificar quatro grupos de estações com comportamento similar no que se refere aos processos pluviométricos. Esta pesquisa permitiu conhecer o comportamento espacial e temporal da precipitação, caracterizada pela marcada sazonalidade, produto da influência direta da Zona de Convergência Intertropical. A tendência mostrou um padrão de distribuição espacial com uma gradação que vai de menor à maior no sentido nordeste à sudeste. Conclusões. Este estudo permitiu estimar a regularidade espacial do comportamento da chuva e do grau da heterogeneidade deste elemento climático ano após ano, que ao mesmo tempo representa o início do planejamento estratégico ao nível regional.

Morfogênese de braquiárias sob estresse hídrico / Morphogenesis of Brachiarias species under water stress

Objetivou-se avaliar Urochloa spp. submetida a duas situações de estresse hídrico: déficit e alagamento. As forrageiras estudadas foram: U. humidicola cv. Tully, U. humidicola cv. Llanero, U. brizantha cv. BRS Piatã, U. brizantha cv. Xaraés, U. decumbens cv. Basilisk e U. ruziziensis cv. Kenedy, e os parâmetros avaliados foram relacionados às características estruturais e morfogênicas. O trabalho foi desenvolvido em casa de vegetação pertencente à Unidade Universitária de Aquidauana. Os tratamentos consistiram em diferentes condições de umidade do solo: 50 e 80% da capacidade de retenção de umidade do solo, e lâminas de 0cm, 1cm e 5cm de água acima do solo, com quatro repetições, em delineamento inteiramente ao acaso. O modelo considerou o efeito de umidade do solo para cada espécie forrageira a 5% de significância. As características estruturais e morfogênicas do capim-tully não foram afetadas pelas diferentes condições hídricas aqui avaliadas. O capim-llanero não reagiu ao alagamento. O capim-piatã foi tolerante às condições de déficit hídrico e apresentou mecanismos de adaptação ao alagamento. A U. decumbens cv. Basilisk apresentou respostas adaptativas que melhoram sua tolerância ao alagamento. A U. ruziziensis cv. Kenedy apresentou-se inapta às condições de alagamento e de déficit hídrico.(AU)

The aim of this study was to evaluate braquiarias submitted to two situations of water stress: deficit and flood. The studied forages were: U. humidicola cv. Tully, U. humidicola cv. Llanero, U. brizantha cv. BRS Piatã, U. brizantha cv. Xaraés, U. decumbens cv. Basilisk and U. ruziziensis cv. Kenedy, and the parameters evaluated were related to the structural and morphogenic characteristics. The work was carried out in a greenhouse at the University Unit of Aquidauana. The treatments consisted of different soil moisture conditions: 50 and 80% of the moisture retention capacity of the soil, and slides of 0cm, 1cm and 5cm of water above the soil, with four replications, in a completely randomized design. The model considered the effect of soil moisture for each forage species at 5% of significance. The structural and morphogenic characteristics of grass-tully were not affected by the different water conditions evaluated here. The grass-llanero did not react to flooding. The grass-piatã was tolerant to water deficit conditions and presented adaptation to flooding. The U. decumbens cv. Basilisk presented adaptive responses that improved its tolerance to flooding. The U. ruziziensis cv. Kenedy was unfit for flood and water deficit conditions.(AU)

Aplicación de métodos multivariados para la caracterización de periodos de sequía meteorológica en Venezuela / Application of multivariate methods for the characterization of meteorological drought periods in Venezuela

El análisis multivariado consiste en determinar si existen maneras más simples de representar un conjunto de datos complejo, además de explorar si las observaciones se concentran en grupos y si existe una interdependencia entre los elementos. Este tipo de técnicas se han utilizado ampliamente para analizar datos climatológicos. Es por ello que el objetivo de esta investigación fue caracterizar la ocurrencia de períodos de sequía por medio de series temporales del Índice Normalizado de Precipitación (SPI) para siete localidades agrícolas de Venezuela, mediante el uso de dos métodos multivariados. A través del SPI, se cuantificaron las condiciones de déficit o exceso de precipitación en las localidades agrícolas con una escala mensual del periodo 1980-2014. Para el análisis, se usó la combinación de dos métodos multivariados: el Análisis de Coordenadas Principales de las matrices de datos usando distancia Euclídea y el Análisis de Conglomerados. En las siete localidades se describieron dos o tres grupos de años de SPI. En el caso de las localidades que resultaron con tres grupos (CENIAP, El Cují y Yaritagua) estos se categorizaron en años húmedos, años intermedios y años con déficit hídrico significativo. En tanto que, en el caso de las localidades que resultaron con dos grupos (Turén, Quíbor, Mucuchíes y Bramón) se clasificaron en años húmedos y años asociados al déficit hídrico. La aplicación de estos métodos multivariados permitió identificar los patrones espaciales mensuales dominantes del SPI sobre las localidades estudiadas, además de estar relacionados con la ocurrencia de sequías locales de gran importancia desde el punto de vista agrícola.

Multivariate analysis consists in determining if there are simpler ways to represent a complex set of data, besides exploring if the observations are concentrated in groups and if there is interdependence between the elements. These types of techniques have been widely used to analyze climatological data. That is why the objective of this research was to characterize the occurrence of drought periods by means of time series of the Standard Precipitation Index (SPI) for seven agricultural locations in Venezuela, by using two multivariate methods. The conditions of deficit or excess of precipitation in the agricultural localities were quantified through the SPI with a monthly scale of the period 1980-2014. The combination of two multivariate methods was used for the analysis: Principal Coordinate Analysis of the data matrices using Euclidean distance and Cluster Analysis. Two or three groups of years of SPI were described in the seven locations. In the case of the locations that resulted with three groups (CENIAP, El Cují and Yaritagua), these were categorized in wet years, intermediate years and years with significant water deficit. Meanwhile, in the case of the locations that resulted with two groups (Turén, Quíbor, Mucuchíes and Bramón), they were classified into wet years and years associated with the water deficit. The application of these multivariate methods made it possible to identify the dominant monthly spatial patterns of the SPI on the studied locations, besides being related to the occurrence of local droughts of great importance from the agricultural point of view.

Leaf Amino Acids and Anatomical Traits of Drought Tolerant vs Sensitive Genotypes of Quinoa (Chenopodium quinoa Willd.) under Elevated Levels of Water Stress

Many plants accumulate compatible osmolytes at high levels in plant cells such as amino acids and/or develop special epidermal cell bladders which may serve as external water reservoirs and having small and thick-walled cells in response to water deficit. The objectives of the present investigation were: (i) to study effects of water stress on the anatomical traits and accumulation of free amino acids in quinoa leaves and (ii) to describe differences among drought tolerant and sensitive genotypes in such traits following the imposition of water deficit. A field experiment was carried out in the growing season 2015/2016, using a split plot design with five replications. Main plots were allotted to three irrigation regimes, i.e. well watering (WW) [95% field capacity (FC)], moderate water stress (WS) [65% FC] and severe water stress (SWS) [35% FC] and sub plots to five genotypes. Mean squares due to genotypes, irrigation regimes and their interaction were significant (p≤0.01) for studied leaf free amino acids and anatomical traits. Water stress caused a significant decrease in leaf thickness under WS and SWS, upper and lower epidermis under WS, palisade and spongy layers under SWS, but caused a significant increase in palisade and spongy layers under WS and upper and lower epidermis under SWS. The genotype CICA-17 (tolerant) had the thickest leaf and upper epidermis and second thickest lower epidermis, palisade and spongy layers. Contents of each amino acid were significantly increased due to water stress, except Leucine. Increases in amino acid content increased by increasing severity of water stress. Maximum increase (109.6%) was shown by Threonine under SWS, but minimum (8.08%) was by Arginine under WS. Under SWS, the tolerant genotype CICA-17 showed the highest mean increase percentage (47.9%) in total amount of amino acids relative to WW; it showed the highest increase in all amino acids, especially Proline, Methionine and Phenylalanine.

Mapping QTLs for drought tolerance in a SEA 5 x AND 277 common bean cross with SSRs and SNP markers

Abstract The common bean is characterized by high sensitivity to drought and low productivity. Breeding for drought resistance in this species involves genes of different genetic groups. In this work, we used a SEA 5 x AND 277 cross to map quantitative trait loci associated with drought tolerance in order to assess the factors that determine the magnitude of drought response in common beans. A total of 438 polymorphic markers were used to genotype the F8 mapping population. Phenotyping was done in two greenhouses, one used to simulate drought and the other to simulate irrigated conditions. Fourteen traits associated with drought tolerance were measured to identify the quantitative trait loci (QTLs). The map was constructed with 331 markers that covered all 11 chromosomes and had a total length of 1515 cM. Twenty-two QTLs were discovered for chlorophyll, leaf and stem fresh biomass, leaf biomass dry weight, leaf temperature, number of pods per plant, number of seeds per plant, seed weight, days to flowering, dry pod weight and total yield under well-watered and drought (stress) conditions. All the QTLs detected under drought conditions showed positive effects of the SEA 5 allele. This study provides a better understanding of the genetic inheritance of drought tolerance in common bean.

Photosynthetic capacity and water use efficiency in Ricinus communis (L) under drought stress in semi-humid and semi-arid areas

ABSTRACT Castor bean is one of the crops with potential to provide raw material for production of oils for biodiesel. This species possess adaptive mechanisms for maintaining the water status when subjected to drought stress. A better understanding these mechanisms under field conditions can unravel the survival strategies used by this species. This study aimed to compare the physiological adaptations of Ricinus communis (L.) in two regions with different climates, the semi-arid and semi-humid subject to water stress. The plants showed greater vapor pressure deficit during the driest hours of the day, which contributed to higher values of the leaf temperature and leaf transpiration, however, the VPD(leaf-air) had the greatest effect on plants in the semi-arid region. In both regions, between 12:00 p.m. and 2:00 p.m., the plants presented reduction in the rates of photosynthesis and intracellular CO2 concentration in response to stomatal closure. During the dry season in the semi-arid region, photoinhibition occurred in the leaves of castor bean between 12:00 p.m. and 2:00 p.m. These results suggest that castor bean plants possess compensatory mechanisms for drought tolerance, such as: higher stomatal control and maintenance of photosynthetic capacity, allowing the plant to survive well in soil with low water availability.

Dinâmica do controle químico de Phakopsora pachyrhizi em plantas de soja submetidas a diferentes regimes hídricos / Dynamics of fungicide in chemical control of Phakopsora pachyrhizi in soybean plants subjected to different water regimes

Objetivou-se com este trabalho avaliar a dinâmica do controle químico de Phakopsora pachyrhizi em plantas de soja submetidas a diferentes regimes hídricos. O experimento foi conduzido na área experimental do Instituto Phytus, no município de Itaara, região central do Rio Grande do Sul, na safra 2012/2013. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições, em arranjo fatorial (2x6). O fator A foi composto por dois regimes hídricos: 1) déficit hídrico (50-60% da capacidade de campo); 2) sem déficit hídrico (90-100% da capacidade de campo). O fator B consistiu em quatro intervalos de tempo entre a aplicação de fungicidas e a simulação de chuva (0, 30, 60 e 120 min), uma testemunha com aplicação sem chuva e mais uma testemunha sem aplicação de fungicida. Na aplicação foram utilizados os ingredientes ativos trifloxistrobina + protioconazol (60,0 + 70,0 g i.a.ha-1) com adição de Aureo(r) na dose de 0,375 L.p.c ha-1. Os parâmetros avaliados foram o tempo decorrido entre a aplicação e o surgimento da primeira pústula de ferrugem asiática, a severidade da doença, a produtividade e a massa de grãos. Verificou-se que a aplicação de fungicida em plantas sob déficit hídrico proporciona o maior número de dias para o aparecimento da primeira pústula. A simulação de chuva tem grande efeito na remoção de fungicidas independentemente do regime hídrico. O controle de P. pachyrhizi em plantas sob déficit hídrico foi eficaz, resultando em incrementos de produtividade.(AU)

The objective of this study was to evaluate the dynamics of chemical control of Phakopsora pachyrhizi in soybean plants subjected to different water regimes. The experiment was conducted in the experimental area of Phytus Institute, in Itaara city, central region of Rio Grande do Sul, in 2012/2013 harvest. The experimental design was completely randomized, with four replications in a factorial arrangement (2x6). The first factor was composed of two water regimes: 1) water deficit (50-60% of field capacity); 2) no water deficit (90-100% of field capacity). The B factor was four time intervals between fungicide application and rainfall simulation (0, 30, 60 and 120 min), a witness to application without rain and a control without fungicide application. In application the active ingredients trifloxystrobin + prothioconazole (60.0 + 70.0 g i.a.ha-1) with the addition of Aureo(r) at a dose of 0.375 Lpc ha-1 were used. The parameters evaluated were the number of days until the first pustule preview of Asian rust, disease severity, yield and grain yield. It was found that the fungicide application in plants under water deficit provides the greatest number of days until the first pustule preview. A rainfall simulation has great effect in removing fungicides no matter the water regime. The control of P. pachyrhizi in plants under water deficit was effective, resulting in increased productivity.(AU)

PLASTICIDAD FENOTÍPICA EN PLANTAS DE Lippia dulcis (VERBENACEAE) SOMETIDAS A DÉFICIT HÍDRICO / Phenotypic Plasticity in Plants of Lippia dulcis (Verbenaceae) Subjected to Water Deficit

La plasticidad fenotípica (PF) es un mecanismo mediante el cual las plantas pueden responder a la heterogeneidad ambiental con ajustes morfológicos y fisiológicos. En este estudio se cuantificó la PF de plantas de Lippia dulcis en respuesta a la disponibilidad hídrica en el suelo (baja, moderada y alta), en caracteres morfológicos y de asignación de biomasa, durante la ontogenia vegetativa (días 39, 45, 59 y 66). Nuestra hipótesis planteó que como respuesta a la disponibilidad hídrica, debería esperarse una mayor PF en caracteres morfológicos en comparación con caracteres de asignación de biomasa. La fracción de masa foliar, la razón del área foliar, la longitud de ramas, el número de hojas, así como la razón biomasa de la raíz/biomasa foliar, presentaron la mayor capacidad de ajuste plástico en las plantas de L. dulcis al déficit hídrico, mientras que el área foliar especifica representó el carácter con menor PF a lo largo de la ontogenia vegetativa. La magnitud y patrón de la PF variaron dependiendo del carácter, agua disponible y desarrollo ontogénico. Contrario a nuestra hipótesis, el grupo de caracteres morfológicos y de asignación de biomasa; exhibieron una PF equivalente. Los modelos de asignación óptima y forrajeo óptimo no son mutuamente excluyentes bajo condiciones de déficit hídrico. L. dulcis alteró su patrón de asignación de biomasa, la morfología foliar y la radicular, y como beneficio adaptativo optimizó el balance entre los órganos encargados de la absorción y el uso de agua. L. dulcis exhibió una notable capacidad para evadir el déficit hídrico.

Phenotypic plasticity (FP) is one of the mechanisms by which plants can respond to environmental heterogeneity by adjusting their morphology and physiology. This study tested and quantified the FP of Lippia dulcis plants in response to water availability in soil (low, medium and high), on morphologic and biomass allocation traits during the vegetative ontogeny (days 39, 45, 59 and 66). We hypothesized that in response to water availability, a higher FP should be expected in morphological compared to biomass allocation traits. The leaf mass fraction, leaf area ratio, branch length, number of leaves and root mass/leaf mass ratio, showed the largest capacity of plastic adjustment in the L. dulcis plants to water deficit, whereas the specific leaf area represented the trait with the lowest FP along vegetative ontogeny. The magnitude and pattern of FP changed depending on trait, water availability and ontogenic development. Contrary to our hypothesis the morphological traits and biomass allocation traits showed equivalent FP. The models of optimum allocation and optimum foraging are not mutually exclusive under water deficit. L. dulcis changed its pattern of biomass allocation, leaf and root morphology and as an adaptive advantage optimized the balance between organs involved in water acquisition and use. L. dulcis showed a remarkable ability to avoid water deficit.

Cloning and characterization of a gene encoding novel zinc finger protein transcription factor induced under water deficit stress from rice (Oryza sativa) cv. N-22.

A gene OsZnI encoding Cys3/His1-type zinc finger protein was isolated from the water stress-induced cDNA library of rice (Oryza sativa) cv. N-22, an early maturing, deep-rooted, drought-tolerant genotype adapted to upland conditions. The in-silico analysis revealed an insert of 800 bp with an ORF of 663 nucleotides, encoding 221 amino acids. OsZnI had three distinct features — nuclear localization signal (NLS) present in Arg152-Arg168, Zn finger domain between 185-193 amino acids and 12 amino acids conserved domain in 71-82 amino acids homologous to LEA motif, and belonged to C-type family of Zn finger protein. OsZnI showed induced expression under water deficit stress.