ABSTRACT The development of scaly buds (= cataphylls) has been traditionally associated with seasonally cold climates, although only few species from the southern hemisphere were investigated in this regard. The present work focuses on apical and axillary buds of seven tree species native to the South-American Temperate Rainforests (STR). Due to differences in the lineages from which these species derived, high levels of inter-specific variation in bud structure were expected. Apical and axillary buds were dissected under stereomicroscope, and the sizes of their parent shoots were evaluated. Cataphylls and leaf primordia were counted, and the presence of colleters and/or trichomes registered. Both intra- and inter-specific variations in bud structure were found. The apical buds were scaly in two out of seven species, and naked in the other species. Axillary buds were scaly in all but one species. In general terms, larger shoots developed buds with more organs. The presence of colleters (in four species) was not restricted to those buds lacking an outer cover of cataphylls. Further studies should focus on the relevance at a broader scale of colleters and trichomes as protective structures in tree buds.

SUMMARY: Rainforests (RF) and transitional forests (TF) of Argentinean north Patagonia develop under such different climatic conditions that key aspects of seasonal growth may be assumed to differ among the woody plants that characterize these forests. This study was aimed at evaluating primary growth dynamics in tree species typical of RF and TF. Two common-garden essays were performed in Bariloche, Argentina, one with RF species and the other with TF species. The times of extension initiation and end, the duration of the extension period and the relative and absolute extension rates (RER and AER, respectively) were registered for each species. The relation between AER and air temperature was compared between species. In general, RF species had less variable times of extension initiation, extension end and time of maximum RER, and longer-lasting extension than TF species. Among RF species, extension duration was the longest for Caldcluvia paniculata (26.9 weeks, on average) and the shortest for Luma apiculata (18.9 weeks). Among TF species, the longest and shortest extension durations corresponded, respectively, to Diostea juncea (18.2 weeks) and Maytenus boaria (13.0 weeks). The extension rates of RF species tended to be more related to temperature than those of TF species. This study provides some evidence that endogenous control of growth dynamics would be tighter in TF than in RF species; the former would be better adapted to more severe climatic conditions during the primary-growth period.

RESUMEN: Los bosques lluviosos (RF) y los bosques de transición (TF) de Patagonia Norte argentina, se desarrollan bajo condiciones climáticas contrastantes, por lo que puede esperarse que las especies leñosas que caracterizan estos dos tipos de bosque difieran en aspectos clave del crecimiento estacional. Este estudio tuvo como objetivo evaluar la dinámica de crecimiento primario de especies arbóreas típicas de RF y de TF, mediante dos ensayos en jardín común en Bariloche, Argentina. Para cada especie se registraron las fechas del inicio y fin, y duración del alargamiento. Se calcularon las tasas de alargamiento relativas (RER) y absolutas (AER), relacionando las últimas con la temperatura. En general, las especies de RF tuvieron momentos de inicio del alargamiento, fin de alargamiento y RER menos variables y períodos de alargamiento más largos que las de TF. Entre las especies de RF, Caldcluvia paniculata tuvo el período de alargamiento más largo y Luma apiculata el más corto (26,9 y 18,9 semanas, respectivamente). Entre las especies de TF, Diostea juncea tuvo el período de alargamiento más largo y Maytenus boaria el más corto (18,2 y 13,0 semanas, respectivamente). Las AER de las especies de RF estuvieron más relacionadas con la temperatura que las de TF. Este estudio aporta evidencia que sugiere que la dinámica de crecimiento en especies del TF está sujeta a mayor control endógeno que en especies de RF; las especies del TF estarían mejor adaptadas a condiciones climáticas más estrictas durante el período de crecimiento primario.

Background and aims: Ugni molinae (Myrtaceae) is a shrub species native to Southern Chile - where it is known as "murta" or "murtilla" - and Argentina. This study was aimed at providing morpho-architectural information about U. molinae so as to promote its cultivation and introduction in productive systems of Argentina. M&M: Observations of U. molinae were performed at different scales (plants, foliated axes and annual shoots) for plants developed in natural populations and plants derived from seeds and stem cuttings sampled at the Lago Puelo National Park and its surroundings (Chubut province, Argentina) and grown in nurseries for five years. Results: Short annual shoots of U. molinae complete their extension without branching, whereas long annual shoots may, as they extend, develop branches from intermediate and/or distal nodes. Flowering may start from the second or third year after seed germination or cut rooting. Most flowers develop at the end of spring from basal nodes of growing shoots. Plant structure changes from a clearly hierarchical to a non-hierarchical architecture in the first years of growth. Conclusions: Ugni molinae may be multiplied easily from stem cuttings and seed germination. A short internode and small green leaves associated with it are clear markers of a limit between two successive annual shoots. More detailed studies about the development and productivity of this species in Argentina are necessary in order to evaluate the factibility of its inclusion in productive systems.

Introducción y objetivos: Ugni molinae (Myrtaceae) es una especie arbustiva nativa del sur de Chile - donde se la conoce como "murta" o "murtilla" - y de Argentina. Este estudio tiene como objetivo aportar información morfo-arquitectural de U. molinae, y así promover su cultivo e introducción en sistemas productivos de Argentina. M&M: Se realizaron observaciones de U. molinae a diferentes niveles (planta completa, ejes y brotes anuales) sobre plantas desarrolladas en poblaciones naturales y plantas derivadas de semillas o de enraizamiento de estacas y mantenidas en viveros por cinco años. Resultados: Los brotes cortos de U. molinae completan su extensión sin ramificarse, mientras que los brotes de mayor longitud pueden ramificarse durante su alargamiento a partir de nudos intermedios y/o distales. El inicio de la floración se produce a partir del segundo al tercer año desde la germinación de una semilla o del enraizamiento de una estaca. La mayoría de las flores se forman a fines de la primavera a partir de nudos basales de brotes en alargamiento. La arquitectura de las plantas cambia desde claramente jerárquica a no-jerárquica en los primeros años de desarrollo. Conclusiones: Ugni molinae puede multiplicarse con facilidad a partir del enraizamiento de estacas o de germinación de semillas. El desarrollo de un entrenudo corto asociado a hojas verdes pequeñas es un claro indicador del límite entre brotes anuales sucesivos. Se necesitan estudios más detallados acerca del desarrollo y la productividad de esta especie en la Argentina para evaluar su inclusión en sistemas productivos.