SUMMARYMaytenus vitis-idaea is a bush which reaches 2-5 m in height. It is found in the Paraguayan-Bolivian Chaco and in the north and central regions of Argentina. In addition to its ecological importance, its leaves were used as salt by the native inhabitants of Paraguay and have medicinal value. The objective of this work was to study the physiological quality of M. vitis-idaea seeds cultured in vitro with the purpose to start improvement of biotechnological protocols because its germination is rather unknown and there is no information about in vitro culture for this species. Seeds were tested with the topographical tetrazolium test, and seeds were grown in agar-water (AA) and a medium containing mineral salts and vitamins of Murashige and Skoog (1962) (MS). The following data were recorded: germination percentage, speed of germination (VG) and average time to reach maximum germination (TM). Root and hypocotyls length was measured during 44 days. The tetrazolium test showed 100% viability of the seeds. Germination percentage was significantly higher in the AA medium (62%) than in MS medium (36%) at 20 days after the implantation; germination percentages at 40 days were 92 and 100% for AA and MS, respectively. In vitro culture of M. vitis-idaea seeds in the medium without mineral salts hastened germination and promoted the vigour of the seeds.Key words: Maytenus vitis-idaea, germination, tissue culture. RESUMENMaytenus vitis-idaea es un arbusto de 2-5 m de altura. Se lo encuentra en el Chaco paraguayo-boliviano y norte y centro de Argentina. Además de su importancia ecológica, sus hojas fueron usadas por los indios paraguayos como sal y tienen aplicación medicinal. Con la finalidad de iniciar planes de mejoramiento biotecnológico de M. vitis-idaea, se planteó como objetivo de este trabajo estudiar la calidad fisiológica de las semillas cultivadas in vitro, ya que se trata de una especie poco conocida respecto a su germinación y tampoco se tiene información sobre su cultivo in vitro. Se realizó la prueba topográfica por tetrazolio y se cultivaron semillas in vitro en: agar-agua (AA) y en medio de cultivo con sales minerales y vitaminas de Murashige y Skoog (MS). Se registró: porcentaje de germinación, velocidad de germinación (VG) y tiempo medio para alcanzar la germinación máxima (TM) de las semillas. Se midió la longitud de las raíces y de los hipocótilos durante 44 días. La prueba de tetrazolio arrojó 100% de viabilidad. El porcentaje de germinación en AA a los 20 días (62%) fue significativamente superior que en MS (36%); a los 40 días, los valores de germinación fueron 92 y 100% para AA y MS, respectivamente. El cultivo in vitro de las semillas de M. vitis-idaea en medio sin sales minerales permite adelantar el proceso de germinación y favorece el vigor de las mismas.Palabras clave: Maytenus vitis-idaea, germinación, cultivo de tejidos.

B.A. Bonel, J. Denoia, M. Costanzo, G. Giubileo , G. Zerpa. Paratill effect on a Vertic Argiudol under continued no-tillage systems. Continuous no tillage system has often resulted in soil compactation affecting soil porosity, water movement into the soil profile and plant development. Tillage systems that do not affect surface cover and prevent soil compactation can improve soil properties and increase crop conditions of growth. The objective of this study is to evaluate the effect of a deep tillage system on porosity, aggregation, penetration resistance and soil water infiltration . The study site has been under no tillage for 12 years. The treatments were: SD (direct drilling, no tillage) and SDE (direct drilling, paratill tillage). Results for soil between 0-20 cm, indicate that total porosity, macro and mesoporosity were greater in SDE, while the penetration resistance was lower. For the size aggregate distribution, the mean weigh diameter and the aggregate stability were not different between SD and SDE. Results for soil between 20-35 cm of thickness show soil deterioration due to tillage. Total porosity was lower, while bulk density, penetration resistance and aggregate stability were greater in SDE, because of cohesion increment. Deep tillage improves superficial soil conditions near 20 cm in depth, affecting positively the infiltration rate only near shanks observations.

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