Cells and Tissues
Cards (12)
- Dermal Tissue
- Epidermis (outer covering of plant)
- Protects plant against viruses, bacteria, fungi
- In roots, absorbs water and nutrients
- Has a waxy cuticle that minimizes water loss
- With chloroplasts, outer layer also absorbs light
- Plant Cell
- All plant cells have a cell wall made of cellulose (most abundant polymer on planet, we can’t digest it cause we don’t have the enzyme) - helps out digestive tract, pushes things through as waste
- Central vacuole instead of smaller ones - plants store water in cell
- Not all plant cells have chloroplasts cause they’re not all exposed to the sun (roots, modified leaves like onion bulbs)
- Plasmodesmata - cell to cell communication, send hormones, signals, proteins - adaptation cause plants don’t have circulatory system like animals
- Plant vs. Animal Cells
- Centrioles are used to separate chromosomes during mitosis and meiosis
- Micro tubular organizing centres
- Attach to sister chromatids on metaphase plate
- Dermal Tissue: Stomata
- Gas exchange and water loss (gases come in, oxygen leaves)
- Gas exchange through stoma (plural, stomata) - has guard cells that change shape to open/close stoma - amount of opening varies on plant type and what is being exchanged (gas, water)
- Position of stomata vary on plant type
- Aquatic plants under water - none
- Floating plants - upper surface of leaves only
- Aerial leaves - both sides of leaves
- Dermal Tissue: Trichomes
- Modification of dermal tissue
- Small, hairlike, can be felt with human hand
- Reflect some sunlight to cool plants
- Wind pulls away moisture, almost like sweat - trichomes help plant lose too much water (block air flow, limiting transpiration)
- Some have barbs or toxins to protect from herbivores
- Some trap and digest insects
- Ground Tissue
- Makes up bulk of plant
- Most photosynthesis and carb storage
- 3 tissue types: parenchyma, collenchyma, sclerenchyma
- Ground Tissue: Parenchyma
- Thin primary cell wall
- Most abundant and versatile of all plant cells
- Found in leaves + other green structures
- Have photosynthesis, bulk happens in leaves
- Gas exchange
- Also found in roots to help store starch (no photosynthesis)
- Many are totipotent - retain ability to divide and differentiate - heal wounds, asexual reproduction
- Ground Tissue: Collenchyma
- Unevenly thickened primary cell wall
- Primarily provide flexible structural support
- Often found under the epidermis of stem, especially outside vascular bundles providing support to vascular system
- Ground Tissue: Sclerenchyma
- Toughest of types
- Thin primary cell wall + thick secondary cell wall of cellulose (rigid, non-expandable)
- Dead at maturity
- Two types: fibres (elongated), sclereids (short, variable shapes, function in protection)
- Sclereids - gritty texture in pears
- Vascular Tissue Arrangement
- Monocots - long blades like grass
- Eudicots - leaves like maple leaves
- In eudicot roots, xylem shaped as an x
- Vascular Tissue: Phloem
- Bi-directional
- Moves water as a medium to move sugars, amino acids, proteins, hormones
- End walls with perforations, movement isn’t as fast
- 2 types of living cells
- Sieve-tube elements - long, thing cells with perforated ends called sieve plates - lack nuclei so can’t make proteins + require companion cells to survive
- Companion cells - maintain cytoplasm + plasma membrane of sieve-tube elements
- Plasmodesmata - connect sieve-tube elements with companion cells
- Vascular Tissue: Xylem
- Roots to shoots - bringing water from ground through plant like a straw
- One-way flow
- Water and minerals, nutrients
- No end walls between cells
- Stiffened with lignin, giving them strength to stop it from closing in
- Contains water-conducting cells, parenchyma cells and fibres
- Outer cells dead at maturity
- 2 types of water-conducting cells
- Tracheids - are long, tapered, and contain pits through which water moves
- Vessel elements (in angiosperms) - short and wide, perforations for water transport