La elevada diversidad de especies y endemismos, conjuntamente con la acelerada pérdida de biodiversidad por deforestaciones, destaca la importancia de emprender acciones combinadas de conservación in situ y ex situ. El objetivo de este trabajo fue estudiar la tolerancia a la desecación de las semillas de Prosopis ferox y Pterogyne nitens, para su conservación ex situ a largo plazo en el BGEN. El contenido de humedad (CH) se determinó colocando las semillas de cada población en estufa a 103°C y pesando las muestras a intervalos regulares hasta peso constante. Se realizaron ensayos de germinación en distintos CH: semillas frescas, 10-12%, 3-5%, y en semillas mantenidas seis meses a -20ºC y a 3-5% de CH. El CH de las semillas frescas de P. ferox fue de 14.2% y el de P. nitens de 10% para las dos poblaciones estudiadas. Las semillas de P. ferox llegaron a peso constante a las 17hr y las de P. nitens a las 3hr de secado. La germinación de las semillas de P. ferox fue mayor en los tratamientos con escarificación y la diferencia aumento con la reducción del CH y el almacenamiento. Las semillas de P. nitens con el CH reducido, requieren escarificación. Se concluye que las semillas de ambas especies son probablemente ortodoxas ya que la germinación superó el 80% en las semillas desecadas al 3-5% CH y almacenadas durante seis meses a -20°C.

Desiccation tolerance in seeds of Prosopis ferox and Pterogyne nitens (Fabaceae). The high number of endemisms and species diversity together with the accelerated biodiversity loss by deforestation, especially in North Western Argentina, points out the need to work on species conservation combining ex situ and in situ strategies. The aim of this work was to study the desiccation tolerance in seeds of P. ferox and P. nitens for long term ex situ conservation at the Germplasm Bank of Native Species (BGEN) of the National University of Salta (Argentina). The fruits were collected from ten individuals in P. ferox at the National Park Los Cardones and from two sites (Orán and Rivadavia) for P. nitens. Desiccation tolerance was assessed following previous established methodologies. The moisture content (MC) of the seeds was determined by keeping them in oven at 103°C and weighting the samples at different intervals till constant weight. Germination essays were carried out with two treatments (control and scarification), with different seed MC (fresh, 10-12%, 3-5%) and in desiccated seeds (3-5% MC) stored six months at -20ºC. The MC in P. ferox seeds was 14.2% and 10% in P. nitens, for both populations studied. Percentage germination in P. ferox was higher in the scarification treatments (<82%). The difference between treatments increased with the reduction in MC and the storage for six months at -20°C. Fresh seeds of P. nitens do not need scarification treatment, but it is required with the reduction in MC and storage. Mean germination percentage of desiccated seeds stored six months at -20°C was similar in both populations and greater than 82%.We concluded that both species are probably orthodox because seeds tolerated desiccation to 3-5% and storage for six months at -20°C.

Pre-dispersal seed predation in three populations of the tree Enterolobium contortisiliquum (Fabaceae). Predation is an important selective force that has shaped different strategies related to size, quantity and production time of fruits, seeds and seed reserves. The seeds of E. contortisiliqum are predated by the bruchid Merobruchus bicoloripes. We collected 1 300 fruits from 26 trees in San Salvador de Jujuy (Jujuy province), Castañares, and San Lorenzo (Salta province) Argentina. San Lorenzo is the wettest and highest site, while Castañares is the driest and lowest site. Jujuy is in the middle. In the laboratory, the fruits from each site were weighted and divided in three groups (small, medium and big). We counted the mature and predated seeds per fruit. In San Lorenzo, seed predation was higher in medium sized fruits while in Castañares and Jujuy seed predation was higher in both medium and bigger fruits. However, only in San Lorenzo we found a significant difference in preference for medium size fruits. Rev. Biol. Trop. 57 (3): 781-788. Epub 2009 September 30.