Microscopic and NMR analysis of the external coat from seeds of Magonia pubescens.

• The chemical composition and structure of the layers of the external coat and the three-dimensional organization of the gel during the swelling process are reported here for seeds of Magonia pubescens. • Histochemical-light and scanning electron microscopy (SEM) were used in conjunction with CP-MAS (cross polarization - magic angle spinning: solid state) 13 C NMR spectroscopy to analyse the seed coat layers. • M. pubescens seeds extrude a gel from the second of five regions of the external seed coat when immersed in water. This gel, visualized by SEM, had an extruded cylindrical, laminated structure. Staining revealed two anionic components in the cells of the second layer; the cytoplasm showed the presence of carbohydrates containing vicinal hydroxyl groups and at least some of these carbohydrates were acidic polysaccharides. Part of the ß-linked glucan present in this layer was cellulosic material. Phenolic compounds were not detected in the second layer, but existed in other layers. Lignin and/or tannins were shown in the cell walls of the three innermost layers by CP-MAS 13 C NMR spectroscopy. • The solid-state NMR technique had the advantage of being more sensitive and quantitative compared with light microscropy and might prove to be a useful tool in investigating cell components.

Endophytic Herbaspirillum seropedicae expresses nif genes in gramineous plants.

Abstract The interactions between maize, sorghum, wheat and rice plants and Herbaspirillum seropedicae were examined microscopically following inoculation with the H. seropedicae LR15 strain, a Nif(+) (Pnif::gusA) mutant obtained by the insertion of a gusA-kanamycin cassette into the nifH gene of the H. seropedicae wild-type strain. The expression of the Pnif::gusA fusion was followed during the association of the diazotroph with the gramineous species. Histochemical analysis of seedlings of maize, sorghum, wheat and rice grown in vermiculite showed that strain LR15 colonized root surfaces and inner tissues. In early steps of the endophytic association, H. seropedicae colonized root exudation sites, such as axils of secondary roots and intercellular spaces of the root cortex; it then occupied the vascular tissue and there expressed nif genes. The expression of nif genes occurred in roots, stems and leaves as detected by the GUS reporter system. The expression of nif genes was also observed in bacterial colonies located in the external mucilaginous root material, 8 days after inoculation. Moreover, the colonization of plant tissue by H. seropedicae did not depend on the nitrogen-fixing ability, since similar numbers of cells were isolated from roots or shoots of the plants inoculated with Nif(+) or Nif(-) strains.

Caracterização anatômica das folhas de Cunila microcephala Benth. (Lamiaceae) / Anatomic characterization of Cunila microcephala Benth. (Lamiaceae) leaves

No presente trabalho fez-se a análise da organização estrutural da folhas de Cunila microcephala em microscopia fotônica e microscopia eletrônica de varredura. Seguiram-se as técnicas convencionais no preparo do material para obtenção das lâminas semipermanentes. Para a preparação de lâminas permanentes utilizou-se a técnica de inclusão em glicol metacrilato (GMA). A organização estrutural das folhas desta espécie revela: estômatos em ambas as faces com predominância na face abaxial (folha anti-hipoestomática). Os estômatos da face adaxial são do tipo diacítico. As paredes anticlinais das células epidérmicas da face adaxial são sinuosas e apresentam espessamentos irregulares. As epidermes de ambas as faces são uniestratificadas...