Bromeliads are a conspicuous feature of many Neotropical xerophytic forests. Bromelia serra is an understory bromeliad living in xerophytic forests of the Humid Chaco, which shows high phenotypic plasticity when exposed to different environmental conditions. Its infructescences carry many fleshy fruits that are colonized by arthropods from different feeding guilds. We used structural equation modeling and redundancy analysis to evaluate the influences of light environment, plant size, and infructescence size on the abundance of five different feeding guilds of arthropods dwelling on the infructescences ('fruit-secretion feeders,' 'infructescence-detritus feeders,' 'predators,' 'pulp feeders' or 'seed feeders'). Plant size was negatively associated with canopy openness, whereas infructescence size was positively associated with plant size. The abundance of all feeding guilds, except fruit-secretion feeders, were positively associated with infructescence size.
The Schinopsis balansae forests of the Wet Chaco are characterized by convex areas with woody vegetation and plain areas with herbaceous vegetation. In the Wet Chaco, Aechmea distichantha is a terrestrial bromeliad that forms dense colonies in the understory and open areas of these forests. The aim of this study was to analyze the spatial and temporal variations in population dynamics of this bromeliad species. We monitored ramets growing in sun and shade conditions during two contrasting years. We analyzed the spatial and temporal variations in survival, flowering, and ramet production. Variations in survival, flowering, and ramet production were more marked between years than between habitats. During the year with wetter and milder temperature conditions, survival and ramet production were higher than during the drier year with more extreme temperatures. Survival of vegetative ramets was less variable than survival of young and reproductive ramets. In the colder year, lower winter temperatures reduced the populations in all stages, being more important in the open areas. Our results highlight the importance of low temperatures on A. distichantha demography at this xerophytic forest located at the southernmost distribution range of this bromeliad species.
RESUMEN -Psidium cuneatum Camb., "guayabito o arasá blanco" es una especie nativa de la provincia de Misiones y norte de Corrientes que tiene importancia ecológica y potencial interés comercial. Actualmente está afectada por el avance de la forestación comercial. El objetivo de este trabajo fue analizar el comportamiento germinativo de sus semillas según la madurez de los frutos, las condiciones de germinación y el almacenamiento en diferente ambientes. En individuos marcados y observados semanalmente durante 2 años, se estableció que la fructificación se produce desde diciembre a julio y que los frutos persisten en el árbol durante un período prolongado antes de dispersarse. La germinación de semillas procedentes de frutos de diferentes tamaños, evaluada a través del índice de velocidad de germinación y del porcentaje de germinación permitió determinar que las semillas procedentes de frutos con diámetro mayor a 1.5 cm exhiben mejor comportamiento germinativo, por lo que el tamaño del fruto es un buen indicador de madurez en esta especie. Por otra parte, se estudió el efecto que el régimen de temperatura tiene sobre la germinación, comprobándose que a 27ºC el porcentaje y la velocidad de germinación fueron significativamente superiores. Para establecer las condiciones para la conservación de las semillas se procedió a almacenarlas durante 30, 90, 180, y 270 días, combinando tipo de recipiente y temperatura. Se comprobó que el envase hermético fue más efectivo para la conservación del poder germinativo cuando se utilizó a baja temperatura, aunque se comprobó una reducción acentuada del poder germinativo, el cual fue de 32% a los 180 días.Términos para indexación: Temperatura de germinación, período de almacenamiento, tamaño de frutos. PHYSIOLOGICAL MATURITY, GERMINATION AND CONSERVATION OF GUAYABITO (Psidium cuneatum CAMB. -MYRTACEAE) SEEDSABSTRACT -Psidium cuneatum Camb., "guayabito or arasá blanco" is a species native to the Misiones province and the north of Corrientes, where it is of ecological importance and a potential commercial interest. This species is currently affected by the advance of commercial forestations. The aim of this study was to analyze the germinative behaviour of seeds of this species according to the maturity of the fruits, the germinative conditions and storage under different environments. A few trees were labelled and submitted to weekly observations for two years. It was established that fructification takes place from December to July and the fruits remain on the trees during a long period before they fall off. The germination of seeds from fruits of different sizes, which was assessed by means of the velocity index and germinative percentage, showed that the seeds of fruits with diameter larger than 1.5 cm performed better, so that the fruit size is an appropriate indicator of maturity in this species. On the other hand it was confirmed that 27 ºC is the best temperature for germination percentage and velocity. To establish the best conditions for conserving the seeds, they were sto...
RESUMEN -Bromelia serra Griseb. (Bromeliaceae) es una hierba terrestre que habita en el sotobosque de bosques abiertos del Chaco y el Cerrado. En este trabajo se analizó el efecto de la temperatura, el clima lumínico y la escarificación sobre la germinación de semillas. Se evaluaron dos regímenes de temperatura (15/20 ºC y 20/30 ºC), tres ambientes lumínicos (Luz, Filtro y Oscuridad; 100% luz y 0.65 R:FR, 100% luz y 0.09 R:FR y sin luz respectivamente) y dos tratamientos de escarificación (Escarificación durante 1 min. con H 2 SO 4 al 30% y Control sin escarificar). La temperatura fue un factor clave ya que solo se registró germinación (una reducida fracción de las semillas y en forma lenta) en el tratamiento a 20/30 ºC. Las semillas fueron indiferentes a la intensidad de luz, germinando tanto en condiciones de luz como de oscuridad. La calidad de la luz afectó la germinación, registrándose mayores porcentajes de germinación a altas relaciones R:FR. No se detectaron efectos de la escarificación en la germinación de las semillas. Los resultados de este trabajo aportan información básica sobre la germinación de semillas, que resultan útiles para el manejo de la especie.Términos para indexación: calidad de la luz, Chaco, dormición, semillas herbáceas, manejo.The effects of temperature, light environment and scarification on seed germination of Bromelia serra Griseb. (Bromeliaceae)ABSTRACT -Bromelia serra Griseb. (Bromeliaceae) is a terrestrial herb that grows in the understory of Chaco and Cerrado woodlands. In this study, the effects of temperature, light environment and scarification on seed germination were analyzed. Two temperature regimes (15/20 ºC and 20/30 ºC), three light environments (Light, Filter and Darkness; 100% light and 0.65 R:FR, 100% light and 0.09 R:FR, and without light, respectively) and two scarification treatments (Scarification for 1 min. with H 2 SO 4 at 30% and Control without scarification). Temperature was a key factor because germination was only recorded (a small fraction of seeds and very slowly) at the 20/30 ºC treatment. Seeds were indifferent to light intensity, germinating at full light, as well as at darkness. Light quality affected seed germination, with higher germination percentage at high R:FR. No effect of scarification on seed germination was recorded. The results of this work provide basic information about seed germination that could be useful for the management of this species.
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