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Gravitropism mechanisms in single-celled organs and multicellular organs of plants
Nehasilová, Martina ; Fendrych, Matyáš (advisor) ; Kurtović, Katarina (referee)
Plants react to various environmental stimuli by oriented growth. The growth responses are called tropisms. Gravitropism is a directed growth concerning the gravity vector. Plant shoots grow up, negatively gravitropically, to catch the light. Roots are positively gravitropic; they grow down to anchor the plant in the substrate and seek water and minerals. The process of gravitropism consists of three stages: signal perception, signal transmission, and growth response. These stages can all occur in a single cell or separately in different parts of a multicellular organ. Single-cell gravitropic systems are represented by algal rhizoids or moss protonemata. They need minimal signal transmission because gravity vector perception and growth response happen in the same cell. The multicellular systems, represented here by angiosperm roots, have a more robust signal transmission phase. This thesis compares mechanisms of plant gravitropism based on the two categories - single-cell vs. multicellular. Despite their different cellular arrangements, single-cell and multicellular gravitropism share several characteristics, such as statolith sedimentation, Ca2+ fluxes, pH changes, and altered vesicular trafficking. Still, the lack of knowledge about the single-cell systems and high inner variability within the...
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