Possibilities and limitations of light microscopy in the study of the structure and function of a plant cell

doi wspólne dla całości materiałów konferencyjnychSesja posterowa - XIV Overall Polish in vitro Culture and Plant Biotechnology Conference Structural, physiological and molecular bases of plant differentiation September 14-17, 2015, Pozna

Vessel differentiation in isolated stem segments of Fraxinus excelsior L. after treatment with auxin

Experiments were carried out on isolated stem segments of ash collected from natura! conditions during the winter dormancy season. In order to stimulate cambial activity and vessel difTerentiation the internodes were treated with auxin. The duration of treatment with auxin was difTerent in the particular experimental variants. It appeared that auxin was necessary not only for induction of vessel difTerentiation but also du ring their maturation. The results are discussed on the basis of Sachs· (1981) hypothesis

Terminal vessel and early vessel arrangement in internodes of Fraxinus excelsior.

Application of auxin to the apical end and to the transverse incision in a dissected internode. led to the formation of early vessels in such a way thai the vessels below the incision were abgned with the vessels above it. Thcre was a structural relation between the early vessels and terminal vesscls based on the fact thai the former overlay the latter. A hypothesis is forwarded stating that a template according to which the early vessels find their positions. exists on the surface of terminal wood

Perception of gravity expressed by production of cambial callus in ash (Fraxinus excelsior l.) internodes

In ash internodes isolated from vertical stems during winter dormancy, cambial activity was stimulated by applying an aqueous solution of auxin to the apical end and water to the basal end. The internodes maintained nearly horizontally produced cambial callus at the apical cut surface with more callus on the upper half although both halves were in contact with the same concentration of auxin. A differential response to auxin of the cambium in the upper and lower halves of the horizontally oriented internodes is postulated

Occurrence of circular vessels above axillary buds in stems of woody plants

The circular vcsscls gencrally occur in intact wood stems just above the axillary buds. In this region the cell arrangement with vortices occurs. We interprete the circular vessels as the result or circular polarity in the cambial zone or the region above the axillary bud. The stability or circular polarity in this region is based on the vorticity or the cambium cells arrangement

Plasma membrane and cell wall properties of an aspen hybrid (Populus tremula × tremuloides) parenchyma cells under the influence of salt stress

The effect of salinity on cell turgor, plasma membrane permeability and cell wall elasticity has been measured in petioles of an aspen hybrid using the cell pressure probe. Control plants were grown in soil without the addition of NaCl and treated plants were grown in soil with 50 mM of NaCl for 1, 2, 3 and 4 weeks. In parenchyma cells from Populus tremula 9 tremuloides petioles with an increased level of NaCl in the soil: (a) turgor pressure was reduced after 1 week of treatment but afterward it was similar to untreated plants, (b) the value of elastic modulus of the cell walls increased, and (c) hydraulic conductivity of the plasma membrane of treated plants decreased in comparison to untreated ones. No histological differences and distribution of JIM5 antibody between the petioles of plants grown under salinity and the untreated were found. In cell walls of parenchyma and collenchyma from plants grown under salinity, the presence of pectic epitopes recognized by JIM7 antibodies was increased in comparison to the control plants. The obtained results indicate that under salt stress the permeability of water through plasma membrane is disturbed, cell walls became more rigid but the turgor pressure did not change

Distribution of lipid transfer protein 1 (LTP1) epitopes associated with morphogenic events during somatic embryogenesis of Arabidopsis thaliana

Using immunocytochemical methods, at both the light and electron microscopic level, we have investigated the spatial and temporal distribution of lipid transfer protein 1 (LTP1) epitopes during the induction of somatic embryogenesis in explants of Arabidopsis thaliana. Immunofluorescence labelling demonstrated the presence of high levels of LTP1 epitopes within the proximal regions of the cotyledons (embryogenic regions) associated with particular morphogenetic events, including intense cell division activity, cotyledon swelling, cell loosening and callus formation. Precise analysis of the signal localization in protodermal and subprotodermal cells indicated that cells exhibiting features typical of embryogenic cells were strongly labelled, both in walls and the cytoplasm, while in the majority of meristematic-like cells no signal was observed. Staining with lipophilic dyes revealed a correlation between the distribution of LTP1 epitopes and lipid substances within the cell wall. Differences in label abundance and distribution between embryogenic and non-embryogenic regions of explants were studied in detail with the use of immunogold electron microscopy. The labelling was strongest in both the outer periclinal and anticlinal walls of the adaxial, protodermal cells of the proximal region of the cotyledon. The putative role(s) of lipid transfer proteins in the formation of lipid lamellae and in cell differentiation are discussed

Unmethyl-esterified homogalacturonan and extensins seal Arabidopsis graft union

Background: Grafting is a technique widely used in horticulture. The processes involved in grafting are diverse, and the technique is commonly employed in studies focusing on the mechanisms that regulate cell differentiation or response of plants to abiotic stress. Information on the changes in the composition of the cell wall that occur during the grafting process is scarce. Therefore, this study was carried out for analyzing the composition of the cell wall using Arabidopsis hypocotyls as an example. During the study, the formation of a layer that covers the surface of the graft union was observed. So, this study also aimed to describe the histological and cellular changes that accompany autografting of Arabidopsis hypocotyls and to perform preliminary chemical and structural analyses of extracellular material that seals the graft union. Results: During grafting, polyphenolic and lipid compounds were detected, along with extracellular deposition of carbohydrate/protein material. The spatiotemporal changes observed in the structure of the extracellular material included the formation of a fibrillar network, polymerization of the fibrillar network into a membranous layer, and the presence of bead-like structures on the surface of cells in established graft union. These bead-like structures appeared either “closed” or “open”. Only three cell wall epitopes, namely: LM19 (un/low-methyl-esterified homogalacturonan), JIM11, and JIM20 (extensins), were detected abundantly on the cut surfaces that made the adhesion plane, as well as in the structure that covered the graft union and in the bead-like structures, during the subsequent stages of regeneration. Conclusions: To the best of our knowledge, this is the first report on the composition and structure of the extracellular material that gets deposited on the surface of graft union during Arabidopsis grafting. The results showed that unmethyl-esterified homogalacturonan and extensins are together involved in the adhesion of scion and stock, as well as taking part in sealing the graft union. The extracellular material is of importance not only due to the potential pectin–extensin interaction but also due to its origin. The findings presented here implicate a need for studies with biochemical approach for a detailed analysis of the composition and structure of the extracellular material

Spatio-temporal localization of selected pectic and arabinogalactan protein epitopes and the ultrastructural characteristics of explant cells that accompany the changes in the cell fate during somatic embryogenesis in Arabidopsis thaliana

During somatic embryogenesis (SE), explant cells undergo changes in the direction of their differentiation, which lead to diverse cell phenotypes. Although the genetic bases of the SE have been extensively studied in Arabidopsis thaliana, little is known about the chemical characteristics of the wall of the explant cells, which undergo changes in the direction of differentiation. Thus, we examined the occurrence of selected pectic and AGP epitopes in explant cells that display different phenotypes during SE. Explants examinations have been supplemented with an analysis of the ultrastructure. The deposition of selected pectic and AGP epitopes in somatic embryos was determined. Compared to an explant at the initial stage, a/embryogenic/totipotent and meristematic/pluripotent cells were characterized by a decrease in the presence of AGP epitopes, b/the presence of AGP epitopes in differentiated cells was similar, and c/an increase of analyzed epitopes was detected in the callus cells. Totipotent cells could be distinguished from pluripotent cells by: 1/the presence of the LM2 epitope in the latest one, 2/the appearance of the JIM16 epitope in totipotent cells, and 3/the more abundant presence of the JIM7 epitope in the totipotent cells. The LM5 epitope characterized the wall of the cells that were localized within the mass of embryogenic domain. The JIM8, JIM13 and JIM16 AGP epitopes appeared to be the most specific for the callus cells. The results indicate a relationship between the developmental state of the explant cells and the chemical composition of the cell walls

Integument cell differentiation in dandelions (Taraxacum, Asteraceae, Lactuceae) with special attention paid to plasmodesmata

The aim of the paper is to determine what happens with plasmodesmata when mucilage is secreted into the periplasmic space in plant cells. Ultrastructural analysis of the periendothelial zone mucilage cells was performed on examples of the ovule tissues of several sexual and apomictic Taraxacum species. The cytoplasm of the periendothelial zone cells was dense, filled by numerous organelles and profiles of rough endoplasmic reticulum and active Golgi dictyosomes with vesicles that contained fibrillar material. At the beginning of the differentiation process of the periendothelial zone, the cells were connected by primary plasmodesmata. However, during the differentiation and the thickening of the cell walls (mucilage deposition), the plasmodesmata become elongated and associated with cytoplasmic bridges. The cytoplasmic bridges may connect the protoplast to the plasmodesmata through the mucilage layers in order to maintain cell-to-cell communication during the differentiation of the periendothelial zone cells