HL 1 Biology

9.1 Plant Structure

<<Plant Science>>

Meristems: the tissue in plants consisting groups of cells which help plants continue to grow indefinitely

Apical Meristems: primary meristems, which are found at the tips of stems and roots

Dicotyledonous plant: a flowering plant with 2 embryonic seed leaves

The diversity of plant form related to habitats & adaptations of plants


  • grow upward
  • produce leaves, branches
  • lower parts = support larger mass
  • terrestrial plants support themselves with: turgid cells (rigid from high pressure), cells that have thickened cellulose cell walls, and xylem tissue (make it woody/hard)
  • flowering plants: monocotyledons and dicotyledons
  • Lateral meristem: develops between xylem and phloem and cells produced into more of both tissues
  • most xylem produced = grow tallest

<<Leaf Structure and Adaptations>>

  • leaves produced by apical meristem 
  • vary in size and shape
  • leaves = organs, since composed of groups of different tissues

<<Monocotyledons and Dicotyledons>>

  • anigospermophytes: plants that produce seeds enclosed inside fruits
  • anigospermophytes 2 important groups: monocotyledons and dicotyledons (monocot, dicot)
  • cotyledons: number of leaves contained in embryo
  • monocotyledon: palms, gingers, grasses, bananas
  • dicotyledons: trees, shrubs, non woody

<<Adaptations of roots, stems and leaves>>

  • principles of plant organs: roots stems and leaves
  • used to build structures needed for water and mineral absorption, support and photosynthesis
  • roots usually absorb water + mineral ions
  • some trees modified


Comparing Stem Structure  (p.118)

1) The areas on the diagram represents areas of a tissue. Inside the diagram, the structures are organelles of cells. 

2) Two similarities in the structure between the monocotyledon stem and the dicotyledon stem include having a cortex tissue and an epidermis.

3) The position of the xylem and phloem in the two types of stem differ for the following reasons. The phloem is placed outside xylem whereas the xylem is positioned towards the inside.

4) Monocotyledon stems cannot thicken in the same way as dicotyledon stems because the monocotyledon does not consist of a lateral meristem, cambium,  between the phloem and xylem. This cambium enables to thicken the stem of the wood as it can create secondary xylem growth. As this cambium exists, it helps the dicotyledon stem to become thick. Thus, since the monocotyledon does not have a cambium, it is not as thick as the dicotyledon.

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