María Angélica Damascos

Fruit Mineral Contents of Six Wild Species of the North Andean Patagonia, Argentina

The fruit mineral contents (K, Ca, Ba, Br, Zn, Co, Cr, Fe, Na, Rb, Cs, and Sr) of four native and two exotic naturalized shrubs growing in different areas of the Andean Patagonian region of Argentina were investigated. Native species Berberis darwinii, Berberis microphylla (Berberidaceae), Aristotelia chilensis (Elaeocarpaceae) and Ribes magellanicum (Saxifragaceae) produce small berries while the fruits of the exotic species Rosa rubiginosa and Rosa canina (Rosaceae) are aggregates of aquenes. They are used to prepare jams, tea, liquors, and ice creams. Native shrub fruits had higher content of Br, Zn, Co, Cr, Fe, Mo, and Na than those of the exotic naturalized species. Rosa species showed the highest contents of Ca and Ba in their fruits (the mean content doubled those of the native plant fruits). The fruit nutrient content found in the studied species was similar or higher than other values reported for fruits of temperate and tropical species in the world.

Fenología foliar y sus caracteres asociados en la especie invierno-verde Aristotelia chilensis (Mol.) Stuntz (Elaeocarpaceae)

Se describe la demografia foliar despues del verano de la especie invierno-verde Aristotelia chilensis, creciendo cerca de la ciudad de San Carlos de Bariloche, Argentina. Se compara su peso especifico foliar (SLM, g m-2) con los valores de especies deciduas y siempreverdes de los bosques andino-patagonicos y de comunidades de otras regiones. El patron de emergencia foliar es intermedio, con un pulso de hojas en primavera (cohorte basal, BC) seguido por la emergencia en forma sucesiva de las restantes hojas (cohorte distal, DC) durante el verano. La senescencia de BC ocurre principalmente en el otono, con una perdida de 11-31 % de su SLM. La DC cae sincronicamente a mediados de primavera y su perdida de SLM en el invierno es de 10-13 %. El SLM de A. chilensis (103.6 ± 6,2 g m-2) es intermedio cuando se compara con los valores medios generales de especies deciduas (73,7 ± 15,9 g m-2) y siempreverdes (154,8 ± 45,8 g m-2). El SLM de las especies deciduas y siempreverdes pertenecientes a tres diferentes bosques cercanos a San Carlos de Bariloche vario significativamente al final de la estacion de crecimiento, mientras que A. chilensis mostro valores mas constantes. La periodicidad en la produccion y senescencia de las hojas en A. chilensis permite el mantenimiento de una cohorte foliar a traves del ano, cubriendo la demanda de carbono para la floracion y la produccion de hojas en primavera. Esto distingue a las especies invierno-verdes de las deciduas a pesar de sus similares tiempos promedio de vida de la hoja, mientras que las especies siempreverdes tienen un ciclo de reemplazo foliar mas largo. Tomando en consideracion las condiciones de crecimiento en cada uno de los bosques estudiados, el tiempo de vida de la hoja no fue el unico factor que determino el valor de SLM de las especies. Esta variable tambien dependeria de multiples estreses, que pueden actuar durante la ontogenesis y la evolucion de la hoja en cada grupo fenologico

Gas exchange and plant growth after defoliation on Leandra lacunosa, a cerrado woody species with continuous leaf production

Morphological and physiological leaf traits were studied on control and defoliated potted Leandra lacunosa young plants. After defoliation, remaining bottom leaves showed no significant change in net photosynthesis and stomatal conductance values with time, but the leaf transpiration rate was higher. The production of the new leaves was greater after defoliation in top defoliated plants. Bottom defoliated plants increased stem extension rates and net photosynthesis transitorily. Two months after defoliation, control and defoliated plants did not differ in stem length and root dry mass values. In spite of smaller area and photosynthetic capacity, remaining bottom leaves were able to compensate top leaves elimination. The effectiveness of this compensatory response, however, depended on the ability of new leaves to escape from herbivores.

Differences in phenology and fruit characteristic between invasive and native woody species favor exotic species invasiveness

Abstract This study evaluates the idea that differences in reproductive phenology and traits between coexisting exotic and native species may promote exotic invasiveness. Reproductive phenology, proportions of flowers setting unripe fruits and ripe fruits (fruit set), abundance and morphology of fruits, and seed viability were compared between two invasive (Crataegus monogyna and Sorbus aucuparia) and six native woody fleshy-fruited species at three sites in temperate forests of northwestern Patagonia, Argentina. Flowering and the onset of fruit ripening occurred later in the exotic species than in most of the native species. The exotic species differed between them in some aspects of the reproductive process: C. monogyna had a higher fruit set, whereas S. aucuparia produced more flowers which offset its low values of fruit set. In both the exotic species and one simultaneously fruiting native species (Schinus patagonicus), high numbers of ripe fruits with a high proportion of viable seeds remained on the plants at a time when fruits of other native species were either scarce or absent (autumn–winter period). Compared to the fruits of S. patagonicus, those of both the exotic species are larger and fleshier. Therefore, the fruits of both the exotic species offer the dispersers, especially birds which were the most important frugivores in these studied temperate forests, a resource that would not be provided by the native plants. The success of these exotic species in Patagonian forests appears to be attributable in part to differences in their reproductive attributes such as fruit phenology and fruit traits such as size and fleshiness.

Gas exchange and leaf specific mass of different foliar cohorts of the wintergreen shrub Aristotelia chilensis (Mol.) Stuntz (Eleocarpaceae) fifteen days before the flowering and the fall of the old cohort

In the beginning of the spring Aristotelia chilensis sheds the old cohort, forms a new one and flowers. Fifteen days before the flowering and the fall we measured net photosynthesis (A), transpiration (E), water use efficiency (WUE), specific leaf mass (SLM) and area and mass of leaves per branch in old and new cohorts. Under low irradiance the old cohort exhibited higher mean values of A and WUE on area bases (P<0.05). Under high irradiance A and WUE on mass bases were higher in new cohort due to its lower SLM (42.10 gm) in relation to old cohort (79.53 gm). Because old cohort showed 3.7 times more dry mass per branch it was able to counterbalance its lower performance on mass bases. It was concluded that old cohort was an important source of carbon during two powerful sink processes in the beginning of the spring: new leaves cohort construction and

Effect of light on the growth and photosynthesis of an invasive shrub in its native range

We studied the growth and photosynthetic capacity of Berberis darwinii shrub growing under different light conditions in their native area of Argentina to test if plant physiology differs from invaded area (using studies carried out in New Zealand). In its native range B. darwinii grows under different light conditions by adjusting shoot and leaf morphology and physiology. Plants of B. darwinii growing under the same light environments show similar physiology in native and invasive ranges. Therefore, intra-specific variations of the functional traits in native area do not condition successful invasiveness.

Infestación de Megastigmus aculeatus (Hymenoptera: Chalcidoidea) en las semillas de rosas exóticas invasoras de comunidades naturales de la Patagonia andina de Argentina

Megastigmus aculeatus Swederus (Hymenoptera: Chalcidoidea) infesta las semillas de especies de Rosa tanto en las areas de origen como en las de invasion. La larva de la avispa se desarrolla consumiendo la totalidad de la semilla. Se analizo la infestacion de M. aculeatus en diferentes poblaciones de Rosa rubiginosa L. y Rosa canina L. y en plantas aisladas de Rosa multiflora Thunb. en areas naturales del Noroeste de la Patagonia, Argentina. En R. rubiginosa, la especie mas abundante, estudiamos la prevalencia y exito de infestacion por la avispa y el posible efecto sobre el tamano del fruto. En este trabajo se presentan los primeros registros de R. rubiginosa y R. canina como especies hospedadoras de M. aculeatus en Argentina y se verifica su ausencia en las semillas de R. multiflora. En R. canina, el porcentaje de frutos infestados por M. aculeatus fue bajo (0-1 % por sitio), no siendo probablemente un factor condicionante de la reducida distribucion de la planta. En R. rubiginosa, ese porcentaje fue alto (31-75 % de frutos infestados por sitio), pero solo el 2-8 % de los aquenios estaban infestados. Considerando los sitios analizados, la distribucion a nivel regional de la infestacion por M. aculeatus en las especies de rosas estudiadas es reducida. El tamano del fruto no es afectado por la infestacion del insecto. Los resultados de este trabajo muestran un bajo impacto actual de M. aculeatus en el control natural de la invasion de las rosas en la region andina de Argentina. Sin embargo, dado que las poblaciones de M. aculeatus podrian ser afectadas por la temperatura, un cambio en esta variable podria incrementar la prevalencia de infestacion de las semillas de estos arbustos a mediano y largo plazo.

Population rules can apply to individual plants and affect their architecture. An evaluation on the cushion plant Mulinum spinosum (Apiaceae)

Growth units of individual plants may be seen as equivalent to individual plants in plant populations. Some of the principles known to rule plant-to-plant interactions in crowded populations may apply to the interactions between growth units in plants.