Morphology and ultrastructure of megaspores and microspores of Isoetes sehnemii Fuchs (Lycophyta)

The morphology and wall ultrastructure of megaspores and microspores of Isoetes sehnemii that grows in Brazil were analyzed as part of the study of the Isoetaceae present in Southern South America. The observations were performed with light, scanning and transmission electron microscopes. The megaspores are trilete, 350-450μm in equatorial diameter. The surface is reticulate. In section, the sporoderm is 100μm thick including the ornamentation. The wall is composed of a siliceous perispore, which consists of short fused flatten, elements forming a three-dimensional mesh. The exospore has two zones of different structure. The endospore is fibrillar. The microspores are monolete, 21-27μm in equatorial diameter. The sporoderm is composed of a sporopollinic rugulate perispore. A space between the paraexospore and the exospore is evident. The exospore is compact. The endospore is fibrillar. The ultrastructural analysis akes hoologies evident concerning structure and organization of the layers belo the perispore in both spore types. A possible similarity and stability in the ultrustructure of the present spores and fossils could be also inferred. In addition, there would be a correlation among the plant habitat, the spore ornamentation and the geographic distribution.

A morfologia e a ultraestrutura da parede de megasporos e microspores de Isoetes sehnemii que crescem no Brasil foram analisados como parte do estudo de Isoetaceae presente no sul da América do Sul. As observações foram realizadas com microscopias de luz e eletrônicas de transmissão e varredura. Os megasporos são triletes com 350-450μm de diâmetro equatorial. A superfície é reticulada. Em secção o esporoderma possui 100μm de espessura incluindo ornamentação. A parede é composta de um perisporo silicoso que consiste de elementos fusionados curtos e achatados formando uma rede tridimensional. O exosporo tem duas zonas com diferentes estruturas. O endosporo é fibrilar. Os microsporos são monoletes, 21-27μm de diâmetro equatorial. A esporoderme é composta por um perisporo esporopolínico rugulado. Um espaço entre o para-exosporo e o exosporo é evidente. O exosporo é compacto. O endosporo é fibrilar. A análise ultraestrutural torna evidente homologias relativas a estrutura e organização das camadas abaixo do perisporo em ambos os tipos de esporos. Uma possível similaridade e estabilidade na ultraestrutura do presente esporo e fósseis pode também ser inferida. Além disso, haveria uma correlação entre o habitat da planta, a ornamentação do esporo e a distribuição geográfica.

Cytological, anatomical and biochemical studies on the side-effect of some pesticides

The invisible side-effects of triazophos and spinosad [insecticides], thiophanate-methyl [fungicide] and 2,4-D [herbicide] on plant were carried out using the bioassay test system of Vicia faba root tips to detect their cytotoxicity. Also, effects on the anatomical and biochemical characteristics were investigated. The obtained data showed that a linear decrease in mitotic index [MI] with increasing pesticide concentration. In addition, a linear correlation between the concentration and percentage of chromosomal abnormalities was recorded in the presently treated pesticides. The EC50 values caused undivided to 50% of total root tip cells were 3.61x10[-6], 1.31x10[-3], 4.85x10[-3] and 35.5 ppm for spinosad, thiophanate-methyl, 2,4-D and triazophos, respectively. The results also revealed that all tested pesticides found to decrease the growth of seedlings by 50 to 60% compared to the control. The normal tissues of stem and root similar to control were obtained in the case of insecticide spinosad and tested fungicide thiophanate-methyl while, malformation of the parenchyma cells and dialysis of the cell walls were observed in the case of herbicide 2,4-D. All tested pesticides significantly decreased the protein content in shoot and root except the herbicide 2,4-D in the case of shoot tissue. The insecticide spinosad increased the DNA content while, insecticide triazophos, fungicide thiophanate-methyl and herbicide 2,4-D reduced the DNA content of shoot and root tissues. It is clear that the effect of tested pesticides depends on pesticide type and plant tissue. In addition, the peroxidase enzyme was high sensitive to the tested pesticides. In similar, all of the tested pesticides shown to be highly esterase inhibitors in the case of shoot tissues. It was clear that there were 5 bands of protein pattern in control sample. The protein bands identical with 95.9 and 56.2 KDa were recorded in all treatment samples. In contrast, the protein band of 40.4 KDa was completely disappeared from the homogenates of all tested treatments, Peroxidase isozyme [58.9 KDa] was appeared in tested fungicide and herbicide treatments. While, the band [30.8 KDa] was disappeared in all treatments. Two major esterase isozymes corresponded to 68.3 and 27.8 KDa were presented. These isozymes were appeared in all pesticide treatments except in the case of spinosad. In general, according to the results of present study it can be stated that; the evaluation of pesticides hazardous effects depends on their side visible effects on the non-target organism did not enough. The invisible side-effect is very important in this response

DNA injury induced by 5-aminouracil and caffeine in G2 checkpoints path of higher plant cells

This work evaluated the qualitative and quantitative cellular changes induced by treatment with 5-aminouracil (5-AU) and a combination of 5-AU and caffeine in plant cells in relation to DNA damage, repaired damage, and residual damage. As biological material, Allium cepa L. root tips were used, grown in filtered water, in darkness, with aeration at constant temperature of 25°C ± 0.5. Cell populations were synchronized using 5 mM caffeine in order to study the effects of 5-AU and caffeine/5-AU combined treatment on the DNA content and their incidence in the entrance to mitosis. The results showed a delay in the G2 period due to induced DNA damage by the 5-AU and caffeine/5-AU combined treatment, shown by aberrant metaphases, anaphases and telophases. The effect of caffeine in the combined treatment was heightened in spite of lengthening the checkpoints route that retains the cells in G2. The existence of G2 checkpoints was shown in the cell population studied, inducing lesions in the DNA, chromosomic aberrations and cellular instability

Microspore culture in Corchorus olitorius: effect of growth regulators, temperature and sucrose on callus formation.

Culture of isolated microspores and of anthers on media containing IAA directed free microspore development to an embryogenic pathway in C. olitorius. The first division of microspores on transfer to culture media was symmetrical in contrast to the asymmetrical division seen in normal development in vivo. Initially, 10-30% microspores divided symmetrically, but only 0.2-1% of the dividing microspores continued dividing and produced multicellular microcalli. About 30% of these microcalli produced callus but only on medium with 2.0 mg/L zeatin and 0.1 mg/L IAA. Incubation in the dark at temperatures of 35 degrees C for 1 day and then 25 degrees C was found effective for induction of first embryonic division in Corchorus. The frequency of microspore callus formation was higher on medium containing either 3% or 5% sucrose. Addition of colchicine and addition of activated charcoal to the above medium did not enhance microspore division in Corchorus olitorius. On transfer to different media most calli produced roots but regeneration of shoots and embryos was not induced.

Hematoxylin: a simple, multiple-use dye for chromosome analysis

A staining mixture of hematoxylin-iron alum combined with a strong hydrochloric hydrolysis was successfully applied for chromosome observation of several kinds of plants and some animals. Slightly different procedures were developed for different materials and objectives. For plant cells, the most important technical aspect was the use of 5 N HCl hydrolysis, which resulted in a very transparent cytoplasm, combined with an intense, specific hematoxylin stain. This technique is recommended for cytogenetical analysis in general, and it is especially indicated for practical classes, due to its simplicity and high reproducibility of results. Moreover, the deep contrast observed makes this technique very useful for sequential staining of cells previously analyzed with other stains, as well as for materials with fixation problems.

Signal transduction networks and the biology of plant cells

The development of plant transformation in the mid-1980s and of many new tools for cell biology, molecular genetics, and biochemistry has resulted in enormous progress in plant biology in the past decade. With the completion of the genome sequence of Arabidopsis thaliana just around the corner, we can expect even faster progress in the next decade. The interface between cell biology and signal transduction is emerging as a new and important field of research. In the past we thought of cell biology strictly in terms of organelles and their biogenesis and function, adn researches focused on questions such as, how do proteins enter chloroplasts? or, what is the structure of the macromolecules of the cell wall and how are the se molecules secreted? Signal transduction dealt primarily with the perception of light (photomorphogenesis) or hormones and with the effect such signals have on enhancing the activity of specific genes. Now we see that the fields of cell biology and signal transduction pathway usually involves multiple organelles of cellular structures Here are some examples to illustrate this new paradigm. How does abscisic acid (ABA) regulate stomatal closure? This pathway involves not only ABA receptors whose location is not yet known, but cation and anion channels in the plasma membrane, changes in the cytoskeleton, movement of water through water channels in the tonoplast and the plasma membrane, proteins with a farnesyl tail that can be located either in the cytosol or attached to a membrane, and probably unidentified ion channels in the tonoplast. In addition there are highly localized calcium oscillations in the cytoplasm resulting from the release of calcium stored in various compartments. The activities of all these cellular structures need to be coordinated during ABA-induced stomatal closure. For another example of the interplay between the proteins of signal transduction pathways and cytoplasmic structures, consider how plants mount defense response against pathogens. Elicitors produced by pathogens bind to receptors on the plant plasma membrane or in the cytosol and eventually activate a large number of genes. This results in the coordination of activities at the plasma membrane (production of reactive oxygen species), in the cytoskeleton, localized calcium oscillations, and the modulation of protein kinases and protein phosphatases whose locations remain to be determined. The movement of ...

Regeneración in vitro y aplicaciones a través del cultivo de células y tejidos vegetales / In vitro regeneration and applications though vegetables of cells and tissues culture

Plant cells by measns of their titopotency and aided by in vitro culture techniques can be induced to perform morphogenesis leading to somatic embryoids and massive clonal multriplication; microspore or pollem can be triggered to tecover haploid plants, then characters expressed via haploidy can be selected and fixed. Protoplasts from different species can lead to recombinations. We report here work done con Carica pubescens, where somatic embryoids were obtained from cells; in Prunus avium androgenesis leading to pollem calli was triggered, while plants were recovered from Nicotiana tabacum anthers. Fusion products were obtained using C. pubescens and C.papaya protoplasts, leading up to calli and shoots