Plants

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    • Plants are multicellular eukaryotes that have cell walls made of cellulose
    • Most plants are autotrophic, but some are parasitic or saprobes
    • Plants take the energy from the sun (solar) and convert it into chemical energy (food). They are the base (producers) in terrestrial food chains and webs.
    • aquatic species can diffuse water through surface
    • terrestrial species‘ roots take up water, and transport that water around the plant
    • aquatic species absorb nutrients and minerals through diffusion
    • terrestrial species need roots to transport nutrients and minerals to main part of plant (xylem tissue)
    • aquatic species use diffusion (mostly blades) to transport food made in the leaves
    • terrestrial species need stems to transport food to main part of plant (phloem tissue)
    • terrestrial plants need a rigid support system to hold up leaves and orient to sunlight
    • aquatic species are surrounded by water, there is no water loss
    • terrestrial species have stomata - small pores on the underside of leaves to prevent water loss
    • aquatic species’ zyogtes/young embryos do not risk drying out
    • Terrestrial species have seeds to protect zygote/embryo, and spores from water drying out
    • phylum byrophyta: no seeds (spores), no vascular tissue (xylem and phloem). Examples include: moss, liverworts, hornwarts
    • phylum pteridophyta: no seeds, have vascular tissue (xylem and phloem). Examples include: ferns, horsetails
    • phylum coniferophyta: seeds (cones), have vascular tissue (xylem and phloem). Examples include: pines, fir, cedar, ”evergreens”
    • phylum angiospermophyta: seeds (flowers), have vascular tissue. Examples include: ”flowering plants”, roses, lilies, strawberries, wheat, grass
    • Roots: Function: anchor the plant, absorb water and mineral.
      Two types: Taproot: very thick primary root with many smaller secondary roots called root hairs (ex. Carrots, radish)
      Fibrous: secondary roots that grow and branch equally, no primary root (ex. Grass, lilies, corn, wheat)
    • Root parts + functions:
      • Epidermis: protection, absorbs water
      • Cortex: storage, transport water to vascular tissue
      • Parenchyma cells: unspecialized -> create bulk
      • Endodermis: encloses vascular tissue -> controls water flow
      • Casparian strip: waterproof strip -> prevents backflow of water
      • xylem: transports water and minerals
      • phloem: transports food/nutrients
    • Roots usually grow downwards because of gravity but maybe also due to negative phototropism (growing away from light)
    • Stems: function: transport water from roots to leaves, structure to hold leaves up to stem
    • Stems parts + functions
      • pith: in the centre, storage + bulk -> originate from embryo
      • vascular cambium: makes vascular tissue
      • xylem: makes water and minerals, “inside“ the vascular cambium
      • sapwood: young xylem (close to cambium)
      • heartwood: older xylem (supports the tree), dormant not functional
      • phloem: moves nutrients, “outside” the vascular cambium
      • cork: protection (”skin of the tree”), made by cork cambium
    • Mature plant cells can grow in length, or expand to store water but do not usually divide for the purpose of growing.
    • Meristematic tissue divides to produce new cells by mitosis.
      • Apical meristem
      • cells at the tips of roots or stems
      • allow plant to grow in length
      • Vascular cambium
      • cells that produce vascular tissue
      • allow plant to grow in width
      • Cork cambium
      • cells that produce cork tissue
      • forms epidermis of the stem (aka “bark”)
    • Leaves function: photosynthesis, use sunlight to make food.
    • Leaf parts and functions:
      • petiole: connection between leaf + stem
      • cuticle: waxy covering -> reduces water loss (from evaporation)
      • epidermis: protection -> makes cuticle
      • palisade mesophyll: specialized for photosynthesis
      • chloroplast: organelle that uses sunlight to make food
      • spongy mesophyll: specialized for gas exchange
      • vascular bundle (vein): xylem + phloem
      • stomata (stoma): pores for gas exchange, can open/close
      • guard cells: open/close stomata (controlled by water pressure)
    • Blade-shaped leaf: broadleaf or deciduous plants
    • needle-shaped leaf: conifers (ex. pine, spruce, fir)
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