A phylogenetic analysis was performed on 67 species of Digitaria belonging to four subgenera and 26 of the 32 sections recognized in Henrard's monograph. The analysis was based on 113 discrete and six continuous morphological characters. In the resulting topologies the genus Digitaria was monophyletic. In spite of the low support for most groupings, several clades were recovered. The subdivision of Digitaria in the four subgenera proposed by Henrard was not supported since the large subgenus Digitaria appears as a paraphyletic assemblage within which the other three subgenera are nested. Nevertheless, the monophyly of some of Henrard's sections was supported. This is the first approach to the phylogeny of Digitaria. Se llevó a cabo un análisis cladístico. Se incluyeron 67 especies de Digitaria pertenecientes a los 4 subgéneros y a 26 de las 32 secciones reconocidas en la monografía de Henrard. El análisis fue basado en 113 caracteres morfológicos discretos y 6 continuos En las topologías resultantes el género Digitaria resultó monofilético. A pesar del bajo soporte de la mayoría de los grupos, fueron recuperados varios clados. Los resultados no fueron consistentes con la subdivisión de Digitaria en 4 subgéneros propuesta por Henrard, ya que el extenso subgénero Digitaria aparece como un agregado parafilético dentro del cual se hallan anidados los otros tres subgéneros. Sin embargo, la monofilia de algunas secciones fue confirmada. El presente estudio constituye el primer análisis filogenético de Digitaria.

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Morphological and physiological responses to freezing were evaluated in two ecotypes of the perennial turfgrass Paspalum vaginatum. Leaf extension rate, number of active meristems, leaf water potential and net photosynthesis were measured on plants of both a commercial cultivar, 'Sea Isle 2000', and a wild ecotype from the Flooding Pampa grasslands of Argentina. Plants were propagated by cloning, cultivated in pots, and examined during 18 consecutive days under two treatments: a non-frozen control treatment (15.5±7 ºC) and a frozen treatment with two stages: Stage 1 with four hours of freezing stress for 10 nights (-5ºC), and Stage 2 with 12 hours of freezing stress for eight nights (five nights at -5ºC and three nights at -8ºC). After these treatments, plants were returned to the outside environment to evaluate shoot injury and post-freezing recovery. Leaf water potential, net photosynthesis and leaf extension rate were significantly higher in the wild ecotype than in the commercial cultivar. Meristem density was reduced after freezing in both ecotypes, but was more pronounced in the commercial cultivar (98.5%) than in the wild ecotype (80%). Thus, the two ecotypes coming from different environments, exhibited different morphological and physiological responses to exposure to freezing temperatures.

Paspalum vaginatum Sw. is a perennial grass originating from tropical and subtropical regions worldwide that plays important ecological and utilitarian roles such as dune stabilisation and erosion control, and is used as a lawn and forage plant. The vegetative morphology of shoots was studied using an architectural approach with the aim of identifying constant features that characterise the architectural unit of this species, describing its developmental dynamics, and exploring the morphological basis of its extraordinary plasticity and adaptability to multiple ecological conditions. Plants of two ecotypes were cultivated in pots outdoors during two consecutive summers, and axes of different branching order were marked for periodical observations. Leaf typology, orientation and position of branches and occurrence and position of reproductive axes were considered. The basic growth pattern arises as a result of extensive plagiotropic growth of axes up to fourth branching order, which initially behave as stolons but can become rhizomes insofar the soil cover increases. Orthotropic floriferous axes up to fifth order develop at the axils of stolons, which can form ‘daughter’ clumps by basal tillering. Despite quantitative differences, both ecotypes share similar architectural features. Architectural analysis provides the basis to predict space occupation dynamics under different environmental conditions of growth.

The aerial growth dynamics of the shoots of the widespread turfgrass Paspalum vaginatum was studied. With the aim of identifying quantitative differential features between two genotypes, plants were cultivated outdoors in pots during two consecutive summers. Axes of different branching order were marked for periodical observation to quantify internode production rate, axis production rate, covering rate and reproductive effort. The genotypes differed significantly in the following quantitative features: plagiotropic vs. orthotropic axes proportion, internode production rate, flowering vs. vegetative tiller ratio, vegetative cover and spatial distribution of the canopy. Knowledge of these features may help to understand the great plasticity and adaptability of this species to multiple environmental conditions.