BI111 Lecture Notes - Lecture 18: The Plant Cell, Hemicellulose, Cell Membrane
Document Summary
Overview of the plant body : almost all plants are photosynthetic autotrophs. Shoot system above ground: photosynthetic leaves, stems, root system below ground, nonphotosynthetic roots, plant bodies are dendritic (spreading and branched in form) Some plant cells have lignified secondary cell wall: cellulose fibres anchored with lignin: stronger and more rigid, creates waterproof barrier (hydrophobic, resistant to decay and attack by microbes. Plant tissue system: form and function: 3 tissue systems, ground. All structurally simple but exhibit important differences: vascular. Soft primary tissues: thin primary cell walls, pliable and permeable to water, often round, air spaces (gas exchange, buoyancy) Collenchyma cells: flexible support, thicker (uneven) primary cell walls (pectin) especially at the corners, elongated cells in strands or sheath like cylinder. Strengthen plant parts still elongating: found adjacent to outer growing tissues and the vascular cambium, metabolically active and meristematic, additional growth stimulated by mechanical stress. Commonly found in fruit and seeds: fibers (support)
