| Popis: |
The structure of the walls of cells which grow, differentiate, and fuse with other cells must be changeable during ontogenesis. An obvious expression of structural change is lysis of the cell wall. Normal (nonpathological) cell wall autolysis seems to appear during different events in the life cycle of plants : active growth and vegetative differentiation (e.g., during extending growth; tip growth of fungal hyphae; differentiation of xylem vessels, of pores in sieve vessels, of milk vessels, and of lysigenic excretion bodies) formation and liberation of reproduction units (e.g., from sporangia and gametangia; lysis of tapetum cells into periplasmodium with Pteridophytes and Spermatophytes ; transitory formation of pits between pollen mother cells ; autolysis of fungal fruit bodies) cell fusions (e.g., of sexual reproduction cells; dissolution of pistil tissue during lysigenic pollen tube growth; formation of anastosomes, clamp connections, and dissolution of septa with hyphae of fungi; fusion of carposporogenic threads with auxiliar cells, and formation of secondary pits in red algae) transition from resting stage to growth (e.g., germination of cysts, zygotes, spores, pollen, and seed) mobilization of wall material during senescence (e.g., in whithering flowers and leaves; lysis of pectic substances in separating zones in stalks of leaves and fruit, and in ripened fruit tissue). |
