Facultad de Agronomia y Agroindustrias

The external morphology of the seeds and the SEM structure of the epicuticular waxes of seeds of three groups of O. ficus-indica naturalized to Argentina, i.e., a spiny red-fruited variety, a spiny orange fruited variety and a spineless yellow-fruited variety, were studied. The seeds of the three groups are not differentiated easily with the naked eye. However, hairs can be observed on the surface of the seeds of the red-fruited group with the aid of a stereomicroscope. All three types of O. ficus-indica have a hilum in the apical or subapical position, but only the red and orange types have an aril. Different kinds of epicuticular waxes and wax granules were observed on the seeds of these Opuntias with SEM techniques. However, the differences in epicuticular wax characteristics were not sufficient to characterize them according to species.

The objectives of this study were (a) to identify individual plants of Prosopis alba and P. pallida that could grow at near seawater salinities to use directly as clonal propagules and to establish seed orchard and (b) to analyse the population structure to aid in future germplasm collections for salinity tolerance in Prosopis. This hydroponic greenhouse study compared the growth and survival of 27 Prosopis families (seed from single mother trees) as a function of salinity from 10 to 45 dS m À1 . Nine P. alba families from one saline area (provenance) near Santiago del Estero, Argentina were compared to 14 P. pallida families from six provenances in Peru and to one family each of P. alba/flexuosa from Chile, P. juliflora from Senegal, P. flexuosa from Argentina and P. ruscifolia from Argentina. The mean of the P. pallida families had a significantly greater survival (61.1% vs. 41.7%) and percentage of seedlings that grew (37.4% vs. 23%) at seawater salinities of 45 dS m À1 than P. alba. Families from P. pallida had the greatest mean growth at the highest salinity but P. alba families were ranked third and sixth from the top in growth. There were little differences in maximum height growth of the individual seedlings from these two species. For P. alba, the percentage of seedlings which survived at the highest salinity level had a lower correlation (r 2 =0.46) with the number of seedlings which grew at that salinity level than for P. pallida (r 2 =0.70). The correlation between mean family growth and maximum individual growth was lower for P. alba (r 2 =0.24) than for P. pallida (r 2 =0.49) suggesting that within P. alba, with a sufficiently high number of seedlings, it would be possible to find individuals with rapid growth rates in most families. Approximately 50 of the most rapidly growing seedlings at the highest salinity level have been repotted to be multiplied by rooting of cuttings and to serve as seed orchards for salt tolerance. Given the success in identifying rapidly growing P. alba individuals from only one provenance in Argentina, more extensive germplasm collections and testing are warranted to locate

Evaluation of microhistology estimation criterias for Sphaeralcea bonariensis (Cav.), Pl Lorentz in different mixtures RESUMEN Sphaeralcea bonariensis (malva) es un componente frecuente en las dietas de caprinos del sistema silvopastoril, del semiárido de la provincia de Santiago del Estero, Argentina. Su cuantificación usando el método microhistológico es dificultosa, debido a la presencia de tricomas desprendidos en los campos microscópicos, sin las epidermis correspondientes. Para estimar correctamente la composición botánica de mezclas de especies forrajeras, se realizaron cuatro mezclas conformadas con S. bonarieinsis, Tillandsia sp, Prosopis nigra y Sorghum halepensis, y cada mezcla con proporciones diferentes. Estas fueron secadas en la estufa, molidas y preparadas según el método microhistológico, confeccionando 20 laminillas por mezcla. Se leyeron al microscopio las frecuencias de aparición de las especies, con el fin de estimar la composición botánica de cada mezcla; las lecturas se consideraron como positivas de acuerdo a dos criterios: 1) sólo fragmentos epidérmicos de malva, sin considerar pelos sueltos, y 2) fragmentos epidérmicos y número de pelos sueltos sin epidermis. Los valores obtenidos se compararon mediante un índice de similitud y se analizaron estadísticamente. Se condujo como un experimento factorial con diseño completamente aleatorizado (4x2). El análisis de la varianza entre los índices de similitud detectó diferencias significativas entre criterio x mezcla, determinando que el criterio 1 es el propuesto cuando la proporción de malva es baja (10 %), pero cuando la proporción supera el 50 %, el criterio más adecuado es el 2. En elevadas proporciones de malva en la mezcla (80 %), la misma fue subvaluada, independiente del criterio seleccionado para su estimación.

The oxygen-reactive species may generate oxidative stress, which could result in degenerative diseases. Antioxidant mechanisms usually act in a coordinated way, and they are grouped in two defense systems: enzymatic and nonenzymatic system. The metallo-dependent enzymes of the organism and the natural substances present in legumes have the capacity to delay, decrease or inhibit the oxidative processes.

Gerente de producto: Alfonso García Bada Mena Supervisor de edición: Mateo Miguel García Supervisor de producción: Zeferino García García INTRODUCCIÓN A LA TERMODINÁMICA EN INGENIERÍA QUÍMICA Prohibida la reproducción total o parcial de esta obra, por cualquier medio, sin autorización escrita del editor DERECHOS RESERVADOS 0 1997 respecto a la quinta edición en español por McGRAW-HILL/INTERAMERICANA EDITORES, S.A. DE C.V. Cedro Núm. 512, Col. Atlampa