No abstract

BACKGROUND: High concentrations of ammonium as the sole nitrogen source may result in physiological and nutritional disorders that can lead to reduced plant growth and toxicity. In this study, we hypothesized that ammonium toxicity in radish seedlings (Raphanus sativus L.) might be mitigated by the incorporation of silicon (Si) into applied nutrient solution. To examine this possibility, we conducted a hydroponic experiment to evaluate the effects of five concentrations of ammonium (1, 7.5, 15, 22.5, and 30 mmol L −1) on the photosynthesis, green color index, stomatal conductance, transpiration, instantaneous wateruse efficiency, and biomass production of radish in the absence and presence (2 mmol L −1) of Si. The experimental design was a randomized block design based on a 2 × 5 factorial scheme with four replicates. RESULTS: The highest concentration of applied ammonium (30 mmol L −1) was found to reduce the photosynthesis, transpiration and total dry biomass of radish seedlings, independent of the presence of Si in the nutrient solution. However, at lower ammonium concentrations, the application of Si counteracted these detrimental effects, and facilitated the production of seedlings with increased photosynthesis, greater instantaneous water-use efficiency, and higher total dry biomass compared with the untreated plants (without Si). Transpiration and stomatal conductance were affected to lesser extents by the presence of Si. CONCLUSION: These findings indicate that the addition of Si to nutrient solutions could provide an effective means of alleviating the unfavorable effects induced by ammonium toxicity at concentrations of less than 30 mmol L −1 .

Con el objetivo de evaluar la asociación entre diferentes formas de aplicación de microorganismos eficientes y la inoculación con Rhizobium en el comportamiento morfológico y productivo del frijol común se desarrolló un experimento en la Cooperativa de Créditos y Servicios “Mártires de Taguasco”, Sancti Spíritus, Cuba, de octubre de 2012 a febrero de 2013 y se utilizó el cv. Cuba cueto. Fueron evaluados dos factores, el primero fue la utilización de Rhizobium (sin y 1 kg/46 kg de semilla) y el segundo fue cuatro formas de aplicación de microorganismos eficientes, sin (0), al surco (100 mg/L), foliares (100 mg/L) y la asociada (surco más la foliar). Los indicadores morfológicos y productivos que se determinaron fueron: promedio de hojas por plantas, altura de las plantas (cm), legumbres por plantas, granos por legumbres, masa de 100 granos (g/100 semillas) y rendimiento (t/ha). Los resultados mostraron que la aplicación asociada al surco más la foliar de microorganismos eficientes comparadas con las otras formas, incrementó los parámetros morfológicos y productivos evaluados como la producción de hojas, altura de la planta, legumbres por planta, granos por legumbre, la masa de 100 semillas y el rendimiento del grano en 153,23 % cuando no fueron inoculadas con Rhizobium y 100,00 % con la inoculación en relación al tratamiento control.

Temperature and other abiotic factors, such water and nutrient availability, play an important role for plants in response to the changing environments. At this regard, both warming and drought might affect the nutrient use efficiency (NUE) and growth of Megathyrsus maximus a C4 forage grass of high interest for cattle feeding. However, the nutrient requirements of this species under climate change are unknown. Therefore, we aimed to evaluate the individual and combined effects of two levels of temperature: ambient and elevated temperature (2°C above ambient temperature), and two levels of soil water availability: irrigated plants and non‐irrigated plants on accumulation of leaf nutrients, NUE and biomass production of M. maximus. Temperature control was performed by a temperature free‐air‐controlled enhancement (T‐FACE) system under field conditions. In general, we observed that warming under well‐irrigated conditions increased the leaf accumulation of most nutrients, improving the NUE of N, P, K, Ca, Mg, Cu, Mn and Zn. Plant growth was also enhanced under warming effects, with higher leaf dry mass accumulation and root development. Meanwhile, drought decreased NUE of K, Ca, B and leaf dry biomass, while root growth was stimulated. The combined effects of warming and drought on nutrient accumulation, NUE and plant growth tended to be greater than the individual effects expected from a single factor; thus, warming mitigated the negative impacts of individual drought. In summary, our findings suggest that warming and drought, both as individual and combined factors, will change the nutrient requirements of M. maximus in tropical ecosystems.

No abstract

Esta investigación tuvo como escenario 4 agroecosistemas de la Provincia de Sancti Spíritus, Cuba. Se estudió la respuesta productiva de diferentes cultivos de hortalizas y granos a la cobertura muerta dispuesta sobre el suelo y al empleo de biofertilizantes en condiciones experimentales de campo y en diferentes tipos de suelo. Dentro de las hortalizas se evaluó la cebolla (Allium cepa L.) y el tomate (Solanum lycopersicum L.); para ambas se utilizó diferentes tipos de cobertura muerta sobre el suelo. Con los granos, se empleó Fitomas-E y Biobras 16 en el cultivo del frijol () y microrganismos eficientes en maíz (Zea mays L.). El diseño experimental para los 4 experimentos fue de bloques al azar. En todos el rendimiento de los cultivos fue superior en las variantes tratadas en relación con el control. Cuando se usó cobertura muerta en cebolla y tomate, el mayor rendimiento se obtuvo con el tratamiento con restos de cosecha de arroz: 14,08 y 31,25 t.ha-1, respectivamente. En el cultivo del frijol (Phaseolus vulgaris L.) la mejor combinación fue la aplicación conjunta de Fitomas E y Biobras 16, con un rendimiento de 2,23 t.ha-1. La producción de maíz fue superior en más del 50% cuando se usó microorganismos eficientes en correspondencia con la variante control. Las prácticas agrícolas evaluadas contribuyeron a mejorar la respuesta productiva en todos los cultivos donde fueron aplicadas.

Response of radish seedlings (Raphanus sativus L.) to different concentrations of ammoniacal nitrogen in absence and presence of siliconRespuesta de las plántulas del rábano (Raphanus sativus L.) a diferentes concentraciones de nitrógeno amoniacal en ausencia y presencia de silicio ABSTRACT RESUMENThere are unknown thresholds about the effects of ammonia toxicity in the cultivation of radish and its prejudice is higher in the root than in the aerial part, been the use of silicon an alternative to mitigate this toxicity. The objective was to evaluate the response of radish crop to different concentrations of an ammonium nutrient solution in the absence and presence of silicon under greenhouse conditions. After 30 days of germination were evaluated photosynthesis, green color index, stomatal conductance, transpiration, leaf area, tap root diameter, dry matter accumulation of nitrogen and silicon in shoot parts and roots respectively. Ammonia toxicity in radish decreased photosynthesis, transpiration, and stomatal conductance, having greater prejudice in the dry matter accumulation of root and aerial part, this effect was mitigated with the presence of silicon in the nutrient solution.Existen dudas sobre los efectos de la toxicidad amoniacal en la fisiología del cultivo del rábano y su perjuicio es mayor en la raíz que en la parte aérea, siendo posible el uso del silicio para mitigar esa toxicidad. Para esto el objetivo fue evaluar la respuesta del cultivo del rábano en función de diferentes concentraciones de NH 4 + en la solución nutritiva en ausencia y presencia de silicio. Posterior a los 30 días de la germinación se evaluaron la fotosíntesis, índice de color verde, conductancia estomática, transpiración, área foliar, diámetro de la raíz, materia seca y acúmulos de nitrógeno y silicio respectivamente en la parte aérea y las raíces de las plantas. La toxicidad amoniacal en el rábano disminuyó la fotosíntesis, la transpiración y la conductancia estomática, habiendo mayor perjuicio en el acúmulo de la materia seca de la raíz y la parte aérea, siendo mitigado este efecto con la presencia de silicio en la solución nutritiva.Key words: beneficial element, abiotic stress, nitrogen; nutrient solution, vegetable.Palabras clave: elemento benéfico, estrés abiótico, solución nutritiva, hortaliza.Nitrogen is the second most required nutrient by vegetables. This element is mainly absorbed in form of nitrate or ammonium, and constitutes amino acids, proteins and enzymes. In this way, it exerts influence on the growth of plant species and on the production of reserve substances and maturation. Ammoniacal nitrogen can bring some benefits to plants, because it acts as an important intermediary in many metabolic reactions (Britto and Kronzucker, 2002), has lower energy expenditure for its metabolism, and dispenses the reduction phases, which are required to the absorption of NO 3 - (Hachiya et al., 2012). However, elevated concentrations of NH 4 + lead to several issues: induces toxicity in plants, may lead to chlorosis in leave...

The cultivated area of soybean has increased worldwide in past decades, including regions with saline soils, strongly decreasing growth and productivity. The use of amino acids (AAs) as buffering compounds against stressful conditions can be a useful strategy to mitigate salt stress in these regions. This study aimed to evaluate the effects of foliar application of AA mixtures on the growth, physiology, and biochemistry traits of salt-stressed soybean plants. A pot experiment was designed as a factorial scheme (4 × 3) in a randomized complete design (RCD). Treatments consisted of four concentrations of AA mixtures of a non-VA application, 0.4 mL L−1, 0.8 mL L−1, and 1.2 mL L−1 (VIUSID Agro® (VA) source), which were combined with non-salt stressed and salt-stressed groups (50 and 100 mmol L−1 NaCl), to analyze improvement in growth and potassium (K+) accumulation, maintenance of relative water content (RWC), net photosynthesis rate (A), transpiration (E), stomatal conductance (gs), and chlorophyll content, and increase of proline accumulation and water use efficiency (iWUE). Moderate and high salinity induced a notable increase in oxidative and ionic biomarkers, coupled with higher Malondialdehyde (MDA) concentration and Na+ accumulation. Alternatively, soybean growth, K+ accumulation, and physiological and biochemical parameters were decreased under salinity. Foliar spraying of AAs drastically increased osmolyte accumulation associated with sustained iWUE and RWC, increased proline accumulation, and improved A, E, gs, and chlorophyll content. Greater outcomes were achieved with the foliar spraying of amino acids at 1.2 mL L−1. Collectively, foliar application of AA mixtures plays an important role in salt stress remediation by modifying important physiological and biochemical processes, thereby resulting in a higher growth of soybean plants.