Macro- and micromorphological study of lagenaria siceraria [molina] standl.

Macro- and micromorphological study of Lagenaria siceraria [Molina] Standl., was carried out with the aim off finding out the characteristic features of the different organs of the plant in both entire and powdered forms

Arbuscular mycorrhizal infection in two morphological root types of Araucaria araucana (Molina) K. Koch / Infección por micorrizas arbusculares en dos tipos de raíces de Araucaria araucana (Molina) K. Koch

Araucaria araucana (Molina) K. Koch is a conifer distributed in the Andean-Patagonian forests in the south of Argentina and Chile. The main objective of this work was to relate the different root classes appearing in A. araucana to mycorrhizal behavior. Samples were collected in three different sites in the Lanín National Park (NW Patagonia, Argentina). Two different root classes were present in A. araucana: longitudinal fine roots (LFR) and globular short roots (GSR). Both had extensive mycorrhizal arbuscular symbiosis (AM) and presented abundant hyphae and coils in root cells, a characteristic of the anatomical Paris-type. Dark septate fungal endophytes were also observed. Values of total AM colonization were high, with similar partial AM% values for each root class. Seasonal differences were found for total and partial colonization, with higher values in spring compared to autumn. Regarding the percentage of fungal structures between root classes, values were similar for vesicles and arbuscules, but higher coil percentages were observed in GSR compared to LFR. The percentages of vesicles increased in autumn, whereas the arbuscule percentages increased in spring, coinciding with the plant growth peak. Results show that both root classes of A. araucana in Andean-Patagonian forests are associated with AM fungi, which may have ecological relevance in terms of the importance of this symbiosis, in response to soil nutrient-deficiencies, especially high P-retention.

La conífera Araucaria araucana (Molina) K. Koch se encuentra distribuida en los bosques Andino-Patagónicos de Argentina y Chile. En este trabajo se relacionaron las diferentes clases morfológicas de raíces presentes en la especie con el comportamiento micorrícico. Las muestras fueron tomadas en tres sitios del Parque Nacional Lanín (NO de Patagonia, Argentina). Se observaron dos clases diferentes de raíces: raíces finas longitudinales (RFL) y raíces cortas globulares (RCG). Ambas clases presentaron una importante simbiosis micorrícico-arbuscular (MA), con abundante desarrollo de hifas intracelulares y rulos, característico del tipo anatómico Paris. También se observaron hifas marrones septadas. Los valores totales de colonización MA fueron altos, con porcentajes parciales similares en cada clase radicular. Se encontraron diferencias estacionales en los porcentajes de infección (totales y parciales), con valores mayores en primavera comparados con los de otoño. Los porcentajes de estructuras fúngicas presentes en cada clase radicular fueron similares para vesículas y arbúsculos, pero se observaron mayores valores de rulos en las RCG que en las RFL. Los porcentajes de vesículas aumentaron en otoño, mientras que los de arbúsculos lo hicieron en primavera, en coincidencia con el pico de crecimiento vegetativo de los árboles. Los resultados muestran una fuerte asociación simbiótica MA con A. araucana y su relevancia en términos ecológicos en respuesta a la deficiencia de nutrientes en el suelo, en especial, a la alta retención de fósforo.

Subcellular localization of cadmium in the root cells of Allium cepa by electron energy loss spectroscopy and cytochemistry.

The ultrastructural investigation of the root cells of Allium cepa L. exposed to 1 mM and 10 mM cadmium (Cd) for 48 and 72 h was carried out. The results indicated that Cd induced several obvious ultrastructural changes such as increased vacuolation, condensed cytoplasm with increased density of the matrix, reduction of mitochondrial cristae, severe plasmolysis and highly condensed nuclear chromatin. Electron dense granules appeared between the cell wall and plasmalemma. In vacuoles, electron dense granules encircled by the membrane were aggregated and formed into larger precipitates, which increase in number and volume as a consequence of excessive Cd exposure. Data from electron energy loss spectroscopy (EELS) confirmed that these granules contained Cd and showed that significantly higher level of Cd in vacuoles existed in the vacuolar precipitates of meristematic or cortical parenchyma cells of the differentiating and mature roots treated with 1 mM and 10 mM Cd. High levels of Cd were also observed in the crowded electron dense granules of nucleoli. However, no Cd was found in cell walls or in cells of the vascular cylinder. A positive Gomori-Swift reaction showed that small metallic silver

Subcellular localization of Cd in the root cells of Allium sativum by electron energy loss spectroscopy.

The ultrastructural investigation of the root cells of Allium sativum L. exposed to three different concentrations of Cd (100 mM, 1 mM and 10 mM) for 9 days was carried out. The results showed that Cd induced several significant ultrastructural changes high vacuolization in cytoplasm, deposition of electron-dense material in vacuoles and nucleoli and increment of disintegrated organelles. Data from electron energy loss spectroscopy (EELS) revealed that Cd was localized in the electron-dense precipitates in the root cells treated with 10 mM Cd. High amounts of Cd were mainly accumulated in the vacuoles and nucleoli of cortical cells in differentiating and mature root tissues. The mechanisms of detoxification and tolerance of Cd are briefly explained.

Subterranean structures and mycotrophy of the achlorophyllous Dictyostega orobanchoides (Burmanniaceae)

Plants of Dictyostega orobanchoides arise from about 1 mm thick rhizomes, which are densely covered by sessile, imbricate, peltate scale leaves. The resulting interfoliar spaces are inhabited by fungal hyphae up to 6 microns thick, often developing vesicle-like bladders. The fungus also colonizes the tissue of the scale leaves, inter- as well as intracellularly, forming vesicles but no arbuscules, and it even penetrates the vascular bundles of the leaves. The rhizome itself does not become infected. The 200 microns thick roots emerge from the rhizome and have a 2-layered cortex and voluminous rhizodermis, which both are delicate and often disrupted or missing. In contrast, the strongly reinforced, tertiary endodermis and the central cylinder are durable and have a considerable tensile strength. Although the roots grow through the hyphal masses in the interfoliar spaces when emerging from the rhizome, they only become infected from the rhizosphere. A collar of rhizomogenous tissue hinders the interfoliar hyphae from direct contact to the roots. Only within the rhizodermis, the mycorrhizal fungus builds coils of heteromorphic hyphae, arbuscule-like structures, and vesicles. Hence, the mycorrhiza in D. orobanchoides is assigned to the arbuscular mycorrhiza. It is hypothezised, that the ephemeral mycorrhizal tissue combined with the durable vascular system of the roots is a strategy to avoid the high costs of protecting the large rhizodermal surface area. The rhizomogenous collar is explained as an extra protection to the tender, young roots, when emerging from the rhizome. The necessity to include other subterranean plant organs along with the roots in future mycorrhizal studies is emphasized.

The laticifer system of Chamaesyce thymifolia: a closed host environment for plant trypanosomatids

Specimens of Chamaesyce thymifolia (Euphorbiaceae) infected and uninfected by Phytomonas sp., a parasite of the Trypanosomatidae family, were anatomically and ultrastructurally analyzed with special emphasis on the laticifer system. C. thymifolia presents branched non-articulated laticifers and was heavily infected by Phytomonas sp. in all collection sites. Infection was often observed in the initial stages inside the vacuole, when the latex particles could be seen. In intermediary stages of laticifer differentiation, Phytomonas sp. were found free in the cytoplasm, inside small vacuoles or in the central vacuole. In differentiated laticifers that had only the plasma membrane, Phytomonas sp. were free in the latex and close to the cell membrane. Infected and uninfected plants showed identical anatomy and ultrastructure and the starch grain numbers in the latex were not reduced in the presence of this flagellate. Biochemical analysis of the latex of infected and uninfected plants presented similar levels of protein, carbohydrate and beta-1,3-glucanase, suggesting that this species is not pathogenic for the host. Besides, all infected plants complete its life cycle. Plants infected with Phytomonas presented occasionally virus like particles and bacteria inside the laticifer tubes.

Macro-and micromorphological study of root, stem and leaf of sonchus oleraceus l. growing in egypt

The macro- and micromorphology of the root, stem and leaf of Sonchus oleraceus L. were presented so as to facilitate its identification both in the entire and powdered forms