Download Plant Structure and Function

Plants:
Structure and Function
A protective
covering that
surrounds the
seed
Makes seeds.
Makes the plant's
food.
Anchor the plant
in place and
absorb water
and other
minerals from
the soil.
Carries water and food
to the rest of the plant.
Grouped by Characteristics
• Vascular
– Three main parts: roots, stems and leaves
• Roots can be different sizes:
– Fibrous and tap roots
• Storage roots: beets, carrots, sweet potatoes and turnips
– Roots have different functions: anchoring the plant, taking in
water and minerals, and store food.
• Nonvascular
– Simple; most grow in moist places
– No vascular tissues.
– Includes mosses, liverworts, hornworts and algae
Vascular Plants: Stems
• Function of Stems
– Support, transport of water & food
• Most stems grow upward
• Some stems grow sideward
– Types of stems
• Green
• Woody
– Transport of materials
• Xylem & phloem
Vascular Plants: Leaves
• Leaves come in variety of shapes and sizes
• Leaves are arranged in different ways
Plant Tissue Groups
Plant Tissues
• A tissue is a group of cells organized to form a
functional unit or a structural unit
• Plants have 3 tissue systems:
– Ground tissue
– Vascular tissue (xylem and phloem)
– Dermal tissue (exterior)
Ground Tissue
• Parenchyma
– Found throughout the plant, these tissues perform
important functions like photosynthesis, food storage, and
secretion
• Collenchyma
– Structural support in herbaceous plants
– Found just under the stem epidermis and along leaf veins
• Sclerenchyma
– Hard structural support (trees)
– May be alive or dead and still function structurally
– One type of sclerenchyma is fiber (wood)
Dermal
• Epidermis - outermost layer composed of
single layer of ground parenchyma cells
• Periderm - many layers thick, found on woody
plants, replaces epidermis, parenchyma cells
Xylem and Phloem
• Both add structural support
• Xylem - conducts water and minerals, long
tapering cells that act as pipes of a sort
• Phloem - conducts food
Root Structure
Root Structure
• Root Cap
– Protects the growing tip of the root and helps it grow down
• Apical meristem
– Root tip where growth occurs
• Zone of Elongation
– Area in plant roots where recently produced cells grow and elongate
prior to differentiation.
• Zone of Maturation
– Cells have differentiated into the different plant tissues
• Root Hairs
– Help absorb water and nutrients
• Vascular Cylinder
– The center of the root occupied by a core of vascular tissue (xylem and
phloem)
Vascular Cylinder
• Xylem
– Tissue whose basic function is to transport water
but will transport some minerals
• Phloem
– Tissue whose basic function is to transport sugars
throughout the plant
Water Transport in the Root
Internal Leaf Structure
Internal Structure
• Cuticle
– Protective covering on the leaf
• Epidermis
– Out layer of cells that helps to protect from water
loss, regulate gas exchange, and secrete metabolic
compounds
– Stomata are found in the leaf epidermis
• Mesophyll
– Interior of the leaf, specialized for photosynthesis
What Prevents Water from Leaving the Plant?
What Prevents Water from Leaving the Plant?
• What type of environmental conditions would
increase transpiration?
– Sunny, warm, dry, windy weather all increase evaporation
• Guard cells control stomata
– Stomata = pores in leaves
– Keep stomata open during day and closed at night
– How do they open? Close?
• Ions move into vacuoles creating concentration gradient
• Water moves into vacuoles via osmosis
• Reverse gradient, lose water
Tree Structure
The Big Question:
How does water
move from roots to
leaves?
Transpiration moves water up xylem vessels
Transpiration moves water up xylem vessels
Transpiration moves water up xylem vessels
Transpiration Moves Water Up Xylem Vessels
• Transpiration exerts an upward pull
– What is responsible for this pull?
• Diffusion! And a bonus – no energy required!!
• The “string” of water is held together by
cohesion and is helped upward by adhesion
• Is known as “transpiration-cohesion-adhesion
mechanism”