Plants

• 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)