|
|
Variability in the response of exodermis to nutrient deficiencies in the environment
Klvaňová, Renáta ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
v angličtině Plant growth and development is largely dependent on the soil environment which is a source of minerals and water needed for plants to survive. However, the availability of these resources in the soil is very heterogenous and important elements can be leached into the lower parts of the soil or bound to soil particles. Plants have therefore developed a number of adaptations during evolution to increase the efficiency of the root system. One of these aspects are the apoplastic barriers (endodermis and exodermis). Both of these layers affect the transport of substances to and from the root, thereby limiting unregulated apoplastic transport through modifications of the cell walls where the polymers that limit the transport of substances are deposited. These are Casparian bands and suberin lamellae. They often differentiate more rapidly when plants are faced with a stress factor such as drought, salinity or toxicity. However, nutrient deficiencies (e.g. N, P, K and Fe) also affect the rate of differentation. Deficiencies can result in both acceleration and deceleration of differentation, which seems to help optimize root transport properties according to the current conditions. However, this reaction has been less studied so far. This work therefore focuses on the analysis of the response...
|
|
|
Uptake of heavy metals - the role of the root system
Homola, Adam ; Tylová, Edita (advisor) ; Mašková, Petra (referee)
Heavy metals are important soil pollutants and pose a significant risk to plants under certain conditions. These include some essential microelements (Fe, Zn, Mn, Mo, Cu, Ni) and toxic metals (e.g. Cd, As, Pb, Hg). Essential microelements have important functions in plants, and are mainly involved in plant metabolism as cofactors of enzymes. Toxic metals have no function, yet they enter the plant in varying degrees from the environment and cause toxicity. However, excessive concentrations of essential metals in the plant also have negative effects and plants have different mechanisms to counteract these negative effects. The bachelor thesis focuses mainly on the uptake of heavy metals from the soil by the root, which is achieved by membrane transporters. It also discusses several mechanisms involved in defence against heavy metal toxicity, not only in terms of regulating uptake, but also after heavy metals have entered plant bodies. These mechanisms are an important aspect of hyperaccumulation, which is also included in this thesis. Hyperaccumulators use these mechanisms on a completely different scale than non-hyperaccumulators, which allows hyperaccumulators to live in environments where heavy metal concentrations are high, making them completely different from each other. The properties of...
|
|
|
Variability and mechanisms of exodermis differentiation in plant roots
Blascheová, Zuzana ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
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...
|
|
|
Root apoplastic barriers in adverse environmental conditions.
Blascheová, Zuzana ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Differentiation of apoplastic barriers in roots is affected by adverse environmental conditions (e.g. heavy metal toxicity, salinity or flooding). The apoplastic barriers, exodermis and endodermis, differ from each other in response to environmental conditions. The exodermis is more affected by these conditions and its occurence is more variable. The presence of differentiated barriers affects root transport features like uptake, accumulation and entrance of polutants or nutrients. Key words: apoplastic barriers, heavy metals, differentiation, root, Casparian strips, suberin lamellae
|
|
|
The role of phytohormones in the root system response to environmental conditions
Vávrová, Barbora ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
During their life cycle, plants form several important anatomical structures in roots, which are crucial for the proper function of the root system and for survival of plant organisms in variable environmental conditions. These structures enable plants to adapt to various stress factors of the environment. Among them, apoplastic barriers are very important. They are formed by cells of the endodermis and exodermis. These cell layers develop Casparian bands and suberin lamellae, modifications of cell walls, that block the apoplastic pathway and are necessary for selective nutrient uptake. Another structure is aerenchyma, a tissue containing many intercellular spaces, which is primarily associated with growth in flooded soils. Development of these structural adaptations is associated with the abscisic acid (ABA) and ethylene. These phytohormones are known mainly for their involvement in stress responses but they are also important in many developmental processes. Work published so far have shown that ABA stimulates deposition of suberin lamellae in the endodermis in unfavourable conditions. Ethylene on the other hand suppresses the deposition of suberin and can even trigger a degradation of previously developed suberin lamellae. In many cases ethylene plays a crucial regulatory role in development of...
|
|
|
Mechanisms of exodermal response to nutrient availability in the environment
Gargoš, Ondřej ; Tylová, Edita (advisor) ; Kummerová, Marie (referee)
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...
|
|
|
Variability and mechanisms of exodermis differentiation in plant roots
Blascheová, Zuzana ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
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...
|
|
|
Root apoplastic barriers in adverse environmental conditions.
Blascheová, Zuzana ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Differentiation of apoplastic barriers in roots is affected by adverse environmental conditions (e.g. heavy metal toxicity, salinity or flooding). The apoplastic barriers, exodermis and endodermis, differ from each other in response to environmental conditions. The exodermis is more affected by these conditions and its occurence is more variable. The presence of differentiated barriers affects root transport features like uptake, accumulation and entrance of polutants or nutrients. Key words: apoplastic barriers, heavy metals, differentiation, root, Casparian strips, suberin lamellae
|
|
|
Cellular mechanisms of differentiation of root apoplastic barriers
Namyslov, Jiří ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Apoplastic barriers (exodermis and endodermis) are primarily used to regulate the free movement of substances within apoplast due to modifications of cell walls. While at the anatomical level, the barriers are studied for a long time, only recently the molecular mechanisms that are behind the emergence of these modifications are gradually identified. The most important modifications are Casparian strips that fill the space between the adjacent cells in exodermis and endodermis. Casparian strips are lignin-based structures formed with the help of CASP proteins located in equatorial region of plasmalema (called CSD membrane domain). In addition to CASP proteins, the formation of Casparian strip involves activity of site-specific enzymes of lignin synthesis (PER64 peroxidase, NADPH oxidase RBOHF). In these cell layers shortly after differentiation of Casparian strips, the deposition of suberin occurs between plazmalema and primary cell wall leading to formation of suberin lamellae also serving to block the apoplast. Next step of differentiation is the formation of U-shaped tertiary thickenings that are formed by deposition of secondary cell wall, whose formation mechanism in the root endodermis is not yet well-known. Processes responsible for formation of apoplastic barriers are thus related to the...
|
|
|
Phylogenic and developmental plasticity of structure of endo and exodermis in roots of higher plants
Szutkowská, Veronika ; Soukup, Aleš (advisor) ; Srba, Miroslav (referee)
Root endodermis and exodermis form apoplastic barriers for the movement of water and solutes into and out of the plant root system. Both layers have modified cell walls with Casparian strips. They often develope suberin lamela as a secondary development stage and thickened cellulose, sometimes lignified, wall as a tertiary development stage. Endodermis, as the innermost layer of cortex, is generally present in all vascular plant roots except Lycopodium. It is very phylogenetically and developmentally stable and in most cases single-layered. Exodermis can be often multi-layered or dimorphic and is formed on the periphery of the root. This layer can be found in a large number of angiosperms but according to the data gathered so far it seems that most of the seedless plants and gymnosperms lack it. Its presence correlates with the environmental conditions in which plants grow and its high structural and developmental plasticity helps roots to resist stress conditions such as drought, salinity, anoxic conditions and the presence of toxic substances. This paper aims to summarize the current knowledge of interspecies variability and developmental plasticity of endodermis and exodermis in roots of vascular plants.
|
guest ::
