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Root system development under drought stress
Svobodová, Barbora ; Soukup, Aleš (advisor) ; Fendrych, Matyáš (referee)
Plants actively react to the environmental conditions in such a way that they can use their resources efficiently and be resistant to suboptimal living conditions (e.g., high salinity, drought stress, high radiation, extremely high or low temperatures, insufficient nutrients etc.). One of the responses to drought stress (DS) is change in root system architecture (RSA). Optimized shape of RSA during drought stress can be under some situations "Steep, cheap and deep" ideotype. Steep - the roots grow in an angle ideally perpendicular to the soil surface. Cheap - most of the resources are spent on growing deeper while having small diameter and lots of aerenchym tissue. Plants with this RSA modulation try to reach deeper parts of the soil with greater water reservoirs and to achieve this, they use a wide range of mechanisms. Another change in RSA in reaction to drought stress, which directs the root to areas with more water is called hydrotropism. The key signal pathway which activates a large variety of drought responsive genes is the abscisic acid (ABA) pathway. Plants also have epigenetic mechanisms, which by remembering a stress factor they have already encountered, are capable of faster and more intensive response.
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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...
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Development related termination of the root apical meristem activity
Benešová, Šárka ; Soukup, Aleš (advisor) ; Vaňková, Radomíra (referee)
Development Related Termination of the Root Apical Meristem Activity Abstract Root system architecture is modulated through growth and branching of individual roots, while the growth is strictly regulated via long term apical meristem (RAM) maintenance and cell elongation. RAM activity is not consistent during root on- togeny, which was shown in several dicotyledonous species as change in root meristem structure and decline in root growth rate during individual root development. This thesis is focused on changes in extent and arrangement of meristematic tissues and their derivatives within adventitious roots of Acorus calamus and Oryza sativa during long term cultivation. Changes in meristem and elongation zone length, the root cap length, radial tissue complexity, as well as the changes in root hair emergence, etc., are put into relation with quantified expression level of selected important regulatory elements taking part in RAM maintenance (WOX and SCR family transcription factors). Methodology and approach for future research in this field are outlined. Keywords: Root, Apical Meristem, Root System Architecture, RAM Termination
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