To test the hypothesis that red-osier dogwood cuttings from a more stressful edaphic environment (dry site) would have a greater salinity tolerance compared with cuttings from a less stressful environment (moist site) a greenhouse experiment was designed. Cuttings collected from three sites in southeastern Manitoba varying in edaphic conditions (moisture) were exposed to 0, 25, 50, or 100 mM NaCl in hydroponics. After four weeks of treatment, physiological parameters were measured. No differences in salinity tolerance were observed between the sites; nevertheless, this study supported previous results suggesting that red-osier dogwood can limit the transport of Na+ from the root to the shoot. To determine the presence of barriers to ion movement, the roots of red-osier dogwood exposed to NaCl were sectioned and observed using brightfield and fluorescence techniques. A modified outer cortical layer was observed suggesting the presence of an exodermis, which would be an additional barrier to Na+ and Cl- movement. Furthermore, the maturation of the endodermis and exodermis occurring closer to the root tip could also contribute to limiting the transport of Na+ to the shoot.

To test the hypothesis that red-osier dogwood cuttings from a more stressful edaphic environment (dry site) would have a greater salinity tolerance compared with cuttings from a less stressful environment (moist site) a greenhouse experiment was designed. Cuttings collected from three sites in southeastern Manitoba varying in edaphic conditions (moisture) were exposed to 0, 25, 50, or 100 mM NaCl in hydroponics. After four weeks of treatment, physiological parameters were measured. No differences in salinity tolerance were observed between the sites; nevertheless, this study supported previous results suggesting that red-osier dogwood can limit the transport of Na+ from the root to the shoot. To determine the presence of barriers to ion movement, the roots of red-osier dogwood exposed to NaCl were sectioned and observed using brightfield and fluorescence techniques. A modified outer cortical layer was observed suggesting the presence of an exodermis, which would be an additional barrier to Na+ and Cl- movement. Furthermore, the maturation of the endodermis and exodermis occurring closer to the root tip could also contribute to limiting the transport of Na+ to the shoot.

Apoplastic barriers (exodermis and endodermis) control free movement of substances by apoplast, which is achieved by specific cell wall modifications. Differentiation of these barriers is to some extent variable. It has been demonstrated many times that the differentiation of root apoplastic barriers is strongly influenced by unfavourable environmental conditions. Many stress factors accelerate the deposition of apoplastic barriers. This work deals with the relationship between availability of nutrients and development of root barriers and mechanisms of coordination of developmental processes in roots, including the involvement of auxin and other phytohormones in the coordination of these processes. The exodermis developmental plasticity is followed in maize (Zea mays L.) under conditions of various nutrient deficiencies. The most important results are presented by anatomical analysis, which shows a significant acceleration of exodermis and endodermis differentiation in the N and P deficiency on the contrary, the slowing of differentiation in the absence of Fe and K. This effect is apparently a result of systemic rather than local root system responses because it was not observed with localized deficiency. This thesis also test the influence of some phytohormones on the development of apoplastic...

Ions in the soil solution traverse many layers (epidermis, exodermis, central cortex, and endodermis) within the root to reach the stele. The endodermis is present in almost all vascular plants while the exodermis is found only in majority of angiosperm roots tested. The maturation of the exodermis and the death of epidermis alter the plasma membrane surface areas (PMSA) potentially available for ion uptake. Do these changes reduce the ion uptake in proportion to the loss of absorptive surface areas? To answer this question onion (Allium cepa L cv. Wolf) adventitious root segments representing above features: Immature Exodermis Live Epidermis (IEXLEP), Mature Exodermis Live Epidermis (MEXLEP), Mature Exodermis Dead Epidermis (MEXDEP) were excised. Using a compartmental elution technique, radioactive sulphate and phosphate present in various internal compartments were quantified. Quantities of ions moved across the plasma membrane, a summation of quantities in the cytoplasm, ‘vacuole’, and ‘bound’ compartments, indicated that the maturation of the exodermis reduces the uptake of sulphate but not phosphate. In contrast, epidermal death reduced the movement of both ions across the plasma membranes. Although there is a reduction in the available PMSA with the maturation of the exodermis and death of the epidermis, these events do not necessarily reduce the ion movement into the plasma symplast. The endodermal cells of onion roots deposit suberin lamellae as secondary walls. As seen in cross-sections some cells remain without these lamellae and are known as ‘passage cells’. What is the pattern of suberin lamella deposition along the root? Is the suberin lamella a continuous layer? To answer these questions, endodermal layers isolated from onion adventitious roots were used in the present study. These layers were observed using four stains (Sudan Red 7B, Fluorol yellow 088 [Fy], berberine, and Nile red) and three microscopes (compound-white light, compound-epifluorescence and confocal scanning). In differentiating cells with and without suberin lamellae in endodermal layers Sudan Red 7B served the best results for compound-white light microscope, Fy for compound-epifluorescence microscope and Nile for confocal laser scanning microscope (CLSM). Suberin lamellae deposition initiated almost in a random manner; they continued to be deposited resulting in the production of longitudinal files alternating with files with passage cells, and were ultimately deposited in almost all cells at a distance of 255 mm from the tip. The suberin lamellae are perforated with pores, a consistent feature even as far as 285 mm from the tip. These pores may serve as portals for water, ions, and pathogen movement.

Ions in the soil solution traverse many layers (epidermis, exodermis, central cortex, and endodermis) within the root to reach the stele. The endodermis is present in almost all vascular plants while the exodermis is found only in majority of angiosperm roots tested. The maturation of the exodermis and the death of epidermis alter the plasma membrane surface areas (PMSA) potentially available for ion uptake. Do these changes reduce the ion uptake in proportion to the loss of absorptive surface areas? To answer this question onion (Allium cepa L cv. Wolf) adventitious root segments representing above features: Immature Exodermis Live Epidermis (IEXLEP), Mature Exodermis Live Epidermis (MEXLEP), Mature Exodermis Dead Epidermis (MEXDEP) were excised. Using a compartmental elution technique, radioactive sulphate and phosphate present in various internal compartments were quantified. Quantities of ions moved across the plasma membrane, a summation of quantities in the cytoplasm, ‘vacuole’, and ‘bound’ compartments, indicated that the maturation of the exodermis reduces the uptake of sulphate but not phosphate. In contrast, epidermal death reduced the movement of both ions across the plasma membranes. Although there is a reduction in the available PMSA with the maturation of the exodermis and death of the epidermis, these events do not necessarily reduce the ion movement into the plasma symplast. The endodermal cells of onion roots deposit suberin lamellae as secondary walls. As seen in cross-sections some cells remain without these lamellae and are known as ‘passage cells’. What is the pattern of suberin lamella deposition along the root? Is the suberin lamella a continuous layer? To answer these questions, endodermal layers isolated from onion adventitious roots were used in the present study. These layers were observed using four stains (Sudan Red 7B, Fluorol yellow 088 [Fy], berberine, and Nile red) and three microscopes (compound-white light, compound-epifluorescence and confocal scanning). In differentiating cells with and without suberin lamellae in endodermal layers Sudan Red 7B served the best results for compound-white light microscope, Fy for compound-epifluorescence microscope and Nile for confocal laser scanning microscope (CLSM). Suberin lamellae deposition initiated almost in a random manner; they continued to be deposited resulting in the production of longitudinal files alternating with files with passage cells, and were ultimately deposited in almost all cells at a distance of 255 mm from the tip. The suberin lamellae are perforated with pores, a consistent feature even as far as 285 mm from the tip. These pores may serve as portals for water, ions, and pathogen movement.

Environmental conditions affect the formation of apoplastic barriers (endodermis and exodermis) in roots. This was shown on many species in many research papers. The exodermal layer is more variable in response to stress conditions than endodermal layer. Cadmium toxicity, as many other stresses, induces faster development of apoplastic barriers. Most of research papers published so far, however characterized only the response of main root to this type of stress factor. Lateral roots, an important part of the root system absorptive surface, are neglected and there is not much information about their response to cadmium stress. The pattern of apoplastic barriers development was therefore analysed in main and also in lateral roots of various size and position on maternal root axis. We found significant differences in response to cadmium stress among these different root types. Then we summed up the differences between these types of roots. Short lateral roots were generally more responsive to cadmium stress, cadmium affected root branching as well as differentiation of apoplastic barriers in lateral roots. These results help us to better understand the response of complex roots system to environmental conditions. In the second part of this work, the role of CASP genes in exodermal development was...

Plants are able to cope with changing environmental conditions or withstand its adverse effects due to their plastic development. One way to adapt to fluctuating amounts of nutrients and water in the environment or the presence of toxic substances is to regulate the movement of substances between the plant and the environment. Beside other, this regulation is also possible at the level of the root system, by the formation of apoplastic barriers endodermis and exodermis. Some species posses endodermis only, in others exodermis in hypodrermal layers of the root can be found. These barriers differentiate in three stages and prevent free movement of coumpounds though apoplast. The transport to the symplast is the key point of regulating the uptake of substances into the plant and the endodermis is the fundamental structure. The presence of exodermis, however, affects the apoplast permeability of the surface root layers and can therefore influence the involvement of the primary cortex cells in the uptake of substances from the environment. In this work the impact of phosphate deficiency on the formation of apoplastic barriers was studied focusing on exodermis and the effect of its differentiation on the occurrence of membrane transporters and involvement of primary cortex cells in the uptake of...

in English The apoplastic barriers of the root (endodermis and exodermis) represent an important regulatory mechanism for the uptake of water and nutrients from the environment, ensuring its selectivity. In addition, both layers respond to stress factors by altering its rate and degree of cell wall modification, which affects the transport properties of the root and represents adaptive plants to high heterogeneity of the soil environment. Apoplastic barriers also respond to the availability of mineral nutrients. This issue has recently been intensively studied and a number of ambiguities persist. Interestingly, the deficiency of some mineral nutrients stimulates the differentiation of barriers, while the deficiency of other mineral nutrients delays the differentiation. In addition, different plant species react differently to the deficiency of the same element. Another interesting aspect is the fact that the reaction of the endodermis and exodermis is localized and takes place mainly in that part of the root system which is directly exposed to the stress factor. This phenomenon has been observed with cadmium toxicity, but more recently with local nutrient deficiencies (nitrogen and potassium) in Zea mays. This diploma thesis deals with the functional significance of localized enhancing or delaying...