Search

ResumenRespuestas al estrés por calor en los cultivos. I aspectos moleculares, bioquímicos y fisiológicos. El objetivo de esta revisión fue integrar los mecanismos por los cuales las plantas responden al estrés por calor a lo largo del continuo suelo-planta-atmósfera, desde una perspectiva agronómica. Esta revisión presenta las bases fisiológicas del estrés por calor, para lo cual se examinaron las temperaturas óptimas y los umbrales de estrés por calor en los cultivos, las metodologías para su estudio, y las respuestas moleculares, bioquímicas y fisiológicas de las plantas a altas temperaturas. Se describe el efecto de las altas temperaturas sobre la estructura y el metabolismo celular, la respiración y la aclimatación de la Q10, la estabilidad de las membranas, la acumulación de osmolitos compatibles, la producción de pigmentos y metabolitos secundarios, la producción de especies reactivas de oxígeno (ROS) y enzimas antioxidantes, la producción de proteínas de estrés, y el efecto sobre la fotosíntesis y la partición de asimilados. Además, se discuten los cambios hormonales que regulan la respuesta de las plantas en el campo, su señalización y la aclimatación al estrés térmico. AbstractCrop physiological responses to high temperature stress. I. Molecular, biochemical and physiological aspects. The objective of this review was to integrate the mechanisms by which plants respond to high temperature stress along the soil-plant-atmosphere continuum, from an agronomic perspective. The review presents the physiological basis underlying thermal stress, for which the optimum and threshold temperatures of crops are examined, along with methodologies for its study and the molecular, biochemical and physiological responses of plants to high temperature. The effects of high temperatures on cell ultrastructure and metabolism, respiration, the acclimation of Q10, membrane stability, accumulation of compatible osmolites, production of pigments, secondary metabolites and stress proteins, production of reactive oxygen species (ROS) and antioxidant enzymes, and the effects on photosynthesis and assimilate partitioning are examined. Hormonal changes and signaling regulating plant responses in the field, and the acclimation to temperature stress are also discussed.

ResumenRespuestas al estrés por calor en los cultivos. II. Tolerancia y tratamiento agronómico. El objetivo de esta revisión fue describir las respuestas de las plantas y los mecanismos de tolerancia al estrés térmico, así como el uso de prácticas agronómicas para mitigar los efectos del estrés por alta temperatura en los cultivos. Se introduce el balance de energía de las hojas y los doseles como enlace entre la temperatura de las plantas y el aire. Se describen los efectos de las altas temperaturas sobre las relaciones hídricas, la fotosíntesis y la partición de los asimilados, y las respuestas morfológicas y fenológicas de algunos cultivos al estrés por calor. Se presenta la agronomía de respuesta para la prevención y remediación del estrés causado por calor, que se abordó desde el punto de vista del mejoramiento genético, del manejo agronómico, la farmacéutica y prácticas hortícolas variadas. Por último, se describen algunas prácticas agronómicas utilizadas para reducir los efectos negativos del estrés por alta temperatura en los cultivos, como el uso de coberturas del suelo, sombra natural o artificial, y la aplicación de sustancias hormonales, protectoras y otros productos de la industria fitoquímica moderna. AbstractCrop physiological responses to high temperature stress. II. Tolerance and agronomic treatment. The objective of this review was to describe plant responses and tolerance mechanisms to thermal stress, as well as the use of agronomic practices to mitigate the effects of high temperature stress on crops. The energy balance of leaves and canopies is presented as a link between plant and air temperature. The effects of high temperatures on water relations, photosynthesis and assimilate partitioning, and the morphological and phenological responses of some crops are described. Response agronomy is presented as a means for the prevention and remediation of thermal stress, which is approached form the perspective of plant breeding, agronomic management, and several pharmaceutical and horticultural practices. Some agronomic practices utilized to reduce the negative effects of high temperature stress on crops are described, such as the use of ground covers, natural or artificial shade, and the application of growth regulators, plant protectants and other products of the modern pharmaceutical industry.

La producción de semillas de calidad es una actividad de alta tecnología que demanda años de investigación y desarrollo y grandes inversiones. A diferencia de la producción de granos, la producción de semillas requiere de cuidados adicionales, mayor precisión en los procedimientos y más capacidades técnicas. Se deben implementar diversos controles para asegurar la pureza genética y la calidad de los atributos fisiológicos de cada variedad. La semilla requiere de un adecuado manejo poscosecha, clasificación, tratamiento y almacenamiento para poder asegurar la calidad y el control de factores como el grado de humedad, la pureza física y varietal, la viabilidad, el contenido de semillas de malezas y la presencia de enfermedades. Las semillas constituyen un insumo básico de la agricultura y representan un pilar estratégico en la producción agropecuaria, son una pieza fundamental de la industria agroalimentaria y de la economía de los países agro-exportadores. El frijol común, es un cultivo cercano a la cultura latinoamericana, su historia corre paralela a la de la Región, transformándose con el paso del tiempo, en un cultivo universal. Desde el sentido antropológico hasta el nutricional, su presencia en los campos de cultivos y las mesas de miles de habitantes del mundo acrecientan su importancia. El presente libro editado por el M.Sc. Rodolfo Araya y el Dr. Marco Gutiérrez son al mismo tiempo un tributo a esta historia además de un recuento fundamental desde el punto de vista científico y de extensión sobre este cultivo. Las contribuciones realizadas por las Universidades, el sector productivo y de Gobierno son por otra parte, un ejemplo de trabajo en equipo y coordinación del sector que sin duda redundará en beneficios tanto para los conocedores y practicantes del sector como para todo aquel que se interese por conocer más sobre esta leguminosa. Los temas abordados van desde la seguridad alimentaria, la fisiología, las plagas, tratamientos poscosecha, calidad, certificación y leyes. Es sin duda un material valioso y una excelente contribución de este equipo de expertos y expertas del campo. Dra. Alice Pérez, Vicerrectora. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM)

La incidencia de la quema de la corona de piña de exportación es un trastorno de origen desconocido, pero probablemente relacionado con estreses fisiológicas originados en el campo y reportado como un problema poscosecha. Se ha sugerido que la aplicación de las ceras empleadas para reducir el deterioro y prolongar la vida poscosecha de los frutos puede ser la causa de este trastorno. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM)

The morphology, growth and physiology of oil palms (Elaeis guineensis Jacq., Deli x Nigeria variety) was characterized at different stages of development of the condition known as ‘dry spear’ or FS (for ‘flecha seca’ in Spanish), and some morpho-physiological indicators associated with a predisposition for the disorder were identified. In Costa Rica, ‘FS’ has symptomology very similar to spear rot or PC (pudrición del cogollo), as it was described in South America. ‘PC’ is a dynamic disorder of complex etiology that affects the development and physiology of palms. The symptomology (‘yellowing’, drying and rotting/) occurs in young leaves and in tissues near the meristem. The aerial symptoms are associated with a deteriorated fine root system. During the initial stages of the disorder in the season with the least precipitation (3.8-73 mm/month), the palms presented low water potential in the leaves, increases in stomatic conductance, reduction in foliage temperature, higher chlorophyll content and reduction of vegetative development. The loss of the fine root system was possibly the cause of the interruption of hormonal ‘signals’ toward the aerial part; which caused the loss of stomatic control of transpiration that led to a hydric, nutritional and energetic imbalance. The anomalous behavior of stomatic conductance and other variables (root density and petiole cross-section), described in a previous article (this journal), is an indicator that could signal conditions of predisposition to a syndrome like PC. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM)

Spear rot or PC (for the Spanish name pudrición del cogollo), known locally in Costa Rica as ‘flecha seca’ is a disorder that affects the development, physiology and yield of the oil palm. It is associated with the deterioration of the fine root system under unfavorable weather and soil conditions. The disorder is not lethal and most palms can overcome the symptoms after a variable period. The hypothesis tested in this work was that it is possible to reduce the severity of the symptoms and eventually the recovery period, using practices that improve the physical and microbiological conditions of the soil to stimulate root growth and improve the nutritional and energy status of the palms. The response obtained was measured using data on morphology, growth, physiology and yield of treated and control palms. In addition, the physical, chemical and microbiological properties of the soil were characterized. To reduce the genetic effect, the study was done with a particular clone that was known to be highly susceptibility to the disorder and that required a long period to recover from the symptoms. The study began when the palms were 28 months old and continued for two years. Two edaphic units (Coarse, Aquic Eutrudept and Medial, Aquic Eutrudept) were identified at the experimental site; where the terrain was irregular, the soil had poor drainage in the first 30 cm, high bulk density, low hydraulic conductivity and few air spaces. All these physical properties favored the presence of standing water during prolonged periods. At the end of the rainy season of 2012, a deterioration of the fine root system was observed when the soil volumetric water content increased above 40%. Imbalances were found between some nutritional elements and in the physiology of the affected palms and later on appeared the typical aerial symptoms of PC: chlorosis and drying of the leaflets at the base of the new leaves and other drying and decay of the petiole bases. The palms that received the recovery treatments showed a remission of symptoms in approximately 18 months, while the control palms were still showing major PC symptoms after two years. Visual (vegetative) recovery was associated with the remediation of the physical, chemical and microbiological properties of the soil, which in turn improved root mass and root health. The nutrient content in the leaves (N, Fe, S and K), root density, trunk height, photosynthesis, fruit production and bunch oil content increased significantly in the recovered palms compared to the untreated controls. Nutrient application (to the soil and the aerial part), and surgical removal of affected tissues in particular, helped to obtain more rapid recovery. It was evident that the removal of necrotic tissue from the petiole bases extended the longevity of the leaves. Nevertheless, the effect sought with the systematic removal of the inflorescences (for the purpose of diverting assimilates to the roots) was not clear. We conclude that the recovery from PC should focus on the regeneration and maintenance of a healthy root system and that the possibilities for success increase when symptomatic palms are treated early. However, emphasis should be placed on prevention, which means taking prompt measures to minimize the negative effects of brusque changes in environmental conditions that could stress the plants. In addition, there should be early detection and immediate correction of any factor or factors (primarily physical, chemical and microbiological aspects of the soil) that could negatively affect the maintenance of a healthy root system. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM) UCR::Vicerrectoría de Docencia::Ciencias Agroalimentarias::Facultad de Ciencias Agroalimentarias

The papaya plant (Carica papaya L.) has been described with a large variety of adjectives, which acknowledge the structural and functional complexity and the high phenotypic plasticity of this giant tropical herb (León 1987). C. papaya, with a somatic chromosome number of 18, is the sole species of this genus of the Caricaceae, a family well represented in the Neotropics, that includes six genera with at least 35 species (Fisher 1980; Ming et al. 2008; Carvalho and Renner 2013 ). Most likely, papaya originated along the Caribbean coast of Mesoamerica (Fitch 2005 ) and spread to many tropical and subtropical regions around the world (Kim et al. 2002), where its distribution is limited by chilling sensitivity (Allan 2002; Dhekney et al. 2007). Domestication eventually led to substantial changes in vegetative growth and sexual forms that distinguish wild populations from cultivated genotypes (Paz and Vázquez-Yanes 1998; Niklas and Marler 2007). Because of its high yield, nutritional value, functional properties, and year-round fruit production, the importance of this crop around the world is undeniable. The papaya plant is a semi-woody, latex-producing, usually single-stemmed, short-lived perennial herb. The relatively small genome of this species shows peculiarities in major gene groups involved in cell size and lignification, carbohydrate economy, photoperiodic responses, and secondary metabolites, which place the papaya in an intermediate position between herbs and trees (Ming et al. 2008 ). Reproductive precocity, high photosynthetic rates of short-lived leaves, fast growth, high reproductive output, production of many seeds, and low construction cost of hollow stems (Fig. 2.1a–d), petioles, and fruits characterize this successful tropical pioneer. High phenotypic plasticity allows this plant to establish in recently disturbed sites, thriving during early stages of tropical succession and as members of diverse agroecosystems as well (Hart 1980; Ewel 1986), that constitute important genetic reservoirs (Brown et al. 2012 ). At any given time, adult papaya plants can sustain vegetative growth, fl owering, and dozens of fruits at different stages of development, simultaneously. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS) UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM)

Las relaciones hídricas en árboles de Enterolobium cyclocarpum del Parque Nacional Santa Rosa, Costa Rica, se estudiaron en diferentes momentos del curso diurno y a lo largo de dos ciclos fenológicos. La característica más sobresaliente de esta especie fue su capacidad de brotar su follaje durante la época de sequía y en condiciones de alta demanda evaporativa. Los resultados mostraron una disminución del potencial hídrico de tallos y raíces gruesas durante la brotación temprana del follaje, de -0,3 MPa a -0,55MPa, evidenciando la contribución de las reservas internas de agua para sustentar este proceso. Se determinó que las hojas jóvenes son las principales responsables de evitar la pérdida de agua y de mantener el balance hídrico durante la estación seca, a juzgar por las conductividades estomáticas bajas y la estabilidad de su potencial hídrico (gs de 50 mmol m-2 s-1; ΨH de -0,75 MPa). El flujo total diario de savia presentó una amplia variación estacional, con transpiraciones diarias de 300 litros durante los meses más lluviosos. Cambios simultáneos en la velocidad del flujo de savia en raíces, tallo y ramas luego de cambios en la radiación indican el alto grado acople entre órganos y la rápida capacidad de respuesta a estímulos ambientales. Este trabajo plantea la importancia de contar con estudios ecofisiológicos que permitan entender mejor los procesos que ocurren en los sistemas forestales. The water relations of Enterolobium cyclocarpum trees of the Santa Rosa National Park, Costa Rica, were studied during different moments of the daily courses and along different periods of the year. The most outstanding feature of this species was its capacity to flush the leaves during the dry season and under conditions of high evaporative demand. The results showed decreased water potentials in stems and coarse roots during early flushing, from -0.3 MPa to -0.55MPa, evidencing the contribution of stem and root water stores in supporting shoot expansion. It was determined that newly flushed leaves constitute a major factor to restrict water loss and to maintain the water balance during the dry season, as observed in the measurements of the stomatal conductance and the leaf water potential (gs de 50 mmol m-2 s-1; ψH de -0.75 MPa). Total daily sap flow showed substantial variations during the year, with daily transpirations of 300 liters during the rainiest months. Simultaneous changes in branch, stem and coarse root sap flow in response to sudden changes in solar radiation indicated that different tree organs were tightly coupled and were highly responsive to environmental changes. This study shows the importance of implementing ecophysiological studies for the best understanding of the processes that occur in forestry systems. The Andrew W. Mellon Foundation/[]//Estados Unidos UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biología UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM)