Juan C. Tivano

Salt Glands in the Poaceae Family and Their Relationship to Salinity Tolerance

The Poaceae is one of the most important Angiosperm families, in terms of morphological diversity, ecology and economic importance. Species within this family show a very wide variation in terms of salinity tolerance. Salt secretion through salt glands plays a significant role in regulating ion balance, contributing to salinity tolerance. This review focuses on salt glands in the Poaceae family and their role in the salinity tolerance. In Poaceae microhairs have been observed in all subfamilies, except Pooideae, but functioning salt glands are reported only in genera belonging to the Chloridoideae subfamily. Structural, ultrastructural and physiological features of salt glands are summarized and discussed and the use of salt glands as potential target features for improving salt tolerance of crops is considered.

Digestión de láminas foliares de Bromus auleticus Trin. ex Nees sometidas a diferentes tiempos de incubación ruminal

A B S T R A C T The decrease in the digestibility of forage is linked with an increase in cell walls and lignification of tissues as they mature. All forages are composed of a heterogeneous group of cell types with particular characteristics that determine the availability of polysaccharides to the rumen’s microorganisms. In the present paper the degradation of Bromus auleticus Trin. ex Nees leaf tissues was studied at different incubation times in the rumen. Samples were taken in two phenological phases: vegetative and pre-flowering, which were submitted to different digestion times in situ on two dry Holando Argentine cows. Simultaneously, leaf blade sections were stained with phloroglucinol acid stain to detect the presence of lignin. Leaf anatomy influenced the degree of tissue digestion, whether due to lignified cell walls or accessibility. After 24 h incubation in the rumen, only the xylem, sclerenchyma and mestome sheath were undigested. The phloem and clorenchyma were digested after 18 h in the pre-flowering phase and 24 h in the vegetative phase. The epidermis was partially digested, and the abaxial epidermis was better digested. The accessibility of carbohydrates in cell walls to the microflora of the rumen is limited by the chemistry of cell walls, and thus, highly organized tissues with secondary lignified walls, such as sclerenchyma and xylem, have a double barrier (physical and chemical) which prevent their digestion.

ESTUDIO ANATOMICO DE VASTAGOS REPRODUCTIVOS EN BROMUS AULETICUS Trin. ex Ness (POACEAE)

El objetivo de este trabajo es caracterizar las variaciones anatomicas que se presentan en organos foliares y caulinares de vastagos reproductivos de Bromus auleticus Trin. ex Ness. Las muestras fueron fijadas en F.A.A., incluidas en parafina-cera, cortadas con micro-tomo rotativo, coloreadas con safranina-fast green en carboxilol y montadas en balsamo de Canada. Ademas, muestras de material fresco fueron cortadas con microtomo de congelacion y luego de la deshidratacion se las coloreo del modo antes descripto, agregandole un pasaje en xilol con eugenol, para montarlas finalmente en balsamo de Canada. Se caracterizan las estructuras foliares y caulinares desde el rizoma hasta el ambito de la inflorescencia. Se describen las variaciones anatomicas observadas en: 1) los organos foliares del rizoma, su transicion hasta hoja plenamente expandida, la hoja distal y las bracteas que conforman las espiguillas; y 2) el rizoma, los entrenudos del vastago aereo, el pedunculo, el eje principal de la inflorescencia, los paracladios primarios y la raquilla. Las variaciones en los componentes foliares estan relacionadas con: a) el desarrollo de estructuras fotosinteticas, b) el desarrollo de espacios lisigenos y c) la distribucion del escleren-quima; y en los componentes caulinares se relacionan con: a) el parenquima cortical y medular, b) el desarrollo y posicion de los haces vasculares y c) el desarrollo del anillo de esclerenquima con ellos asociado

Homogenization and Truncation Processes in Inflorescences of Cyperaceae

This work presents an analysis of the homogenization and truncation processes in Cyperaceae inflorescences. The truncation process is rare in Cyperaceae. There may be homogenized inflorescences but in general these inflorescences present a terminal spikelet. In the few studied cases of truncated inflorescences in Cyperaceae the truncation process may affect the terminal spikelet, only on the main axis and on the long primary branches (species of Cariceae, species of Lipocarpha and Ascolepis), or it may also affect the short branches on the main axis (some species of Kobresia; Cyperus giganteus, C. papyrus and C. prolifer) and on the primary long branches (Cyperus giganteus, C. papyrus and C. prolifer). The homogenized inflorescences can be disjunct or not disjunct. The disjunct homogenized inflorescences have a distal portion of short branches and a proximal portion of long branches, which lead in turn as short branches subunits. Meanhile non-disjunct homogenized inflorescences have only short or long branches, all with the same branching degree.

Anatomía del sistema caulinar subterráneo de Cyperus corymbosus var: subnodosus (Cyperaceae)

Se estudia la anatomia del sistema de ramificacion subterraneo en Cyperus corymbosus Rottb. var. subnodosus (Nees et Meyen) Kuk. Se describe la anatomia del rizoma y del tuberculo en este taxon. Se realiza un analisis comparativo de las variaciones observadas en diferentes estadios de desarrollo. Las caracteristicas anatomicas de rizoma y tuberculos estan asociadas al tipico sistema caulinar subterraneo, a la forma de crecimiento de la especie y a su modo de propagacion vegetativa.