chapter 23 roots, stems and leaves. section 23-1 learning targets describe the organs and tissues of...
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Section 23-1 Learning Targets Describe the organs and tissues of
vascular plants Identify the specialized cells of vascular
tissue Contrast meristematic tissue with other
plant tissues
Specialized Tissues in Plants
Three main organs of plants: ROOTS: underground organs that absorb
water and minerals Also anchor the plant and hold it upright
STEMS: supporting structures that connect roots and leaves
Carry water and nutrients Holds leaves up to light
LEAVES: carry out photosynthesis Capture light, flat so cover more surface area Cuticle and adjustable pores protect leaves from water
loss
Tissue Systems Within the roots, stems and leaves are
FOUR specialized tissue systems: DERMAL TISSUE: forms the skin of a plant (is
the outermost layer of cells) VASCULAR TISSUE: like the plant’s
bloodstream (transports water and nutrients throughout the plant)
GROUND TISSUE: cells between the dermal and vascular tissues
MERISTEMATIC TISSUE: found only in the tips of shoots and roots
Dermal Tissue Outer covering of a
plant Consists of:
Epidermis: outermost layer Cuticle: thick, waxy layer that protects against
water loss and injury (covers epidermis) On under side of leaves, contains guard cells
which regulate water loss and gas exchange
Vascular Tissue Transport system: “bloodstream” Consists of xylem and phloem
Xylem: water-conducting tissue Transports water to leaves
Phloem: food-conducting tissue Takes sugar to the roots
Ground Tissue Tissue that lies between dermal and
vascular tissue Consists of parenchyma, collenchyma
and sclerenchyma
Meristematic Tissue
New growth is produced in cells that make up meristematic tissue
It is the ONLY plant tissue that produces new cells by mitosis!! Best place to see this at the tip of a
shoot/root where apical meristem is located
Section 23-2 Roots Learning Targets Describe the two main types of roots Identify the tissues and structures in a
mature root. Describe the different functions of
roots.
Roots Functions:
Absorb water and nutrients Anchor plant
TWO MAIN TYPES OF ROOTS: Taproots: found mainly in dicots
EX: carrot, dandelions, beets, radishes, oak tree
Fibrous Roots: found mainly in monocots Help to prevent erosion EX: grass
Root Structure Epidermis of root is covered with
tiny projections called root hairs
Increase surface area of root to absorb more water
Roots grow in length as their apical meristem produces new cells near the root tip The fragile new cells are covered by a tough
root cap that protects the root as it forces its way through soil
Root FunctionRoots anchor the plants into
the ground and absorb water and nutrients.
Roots use osmosis and active transport to move water and nutrients into the plant roots to support the plants growth
Section 23-3 StemsDescribe the main functions of stems
Contrast monocot and dicot stems
Explain how primary growth and secondary growth occur in stems
Stems 3 IMPORTANT FUNCTIONS:
Produce Leaves, branches and flowers Hold leaves up in the sunlight Transport substances between roots and
leaves Composed of dermal, vascular and
ground tissue (like the rest of the plant)
Stem Parts Nodes: where
leaves are attached
Internodes: regions between the nodes
Buds: contain undeveloped tissue that can produce new stems and leaves
Primary vs. Secondary Growth
Plants grow in two main ways:Primary Growth: produced by cell divisions in the apical meristem (tips of roots and shoots)
Secondary Growth: the type of growth in which the stem increases in width.
Secondary Growth:WOOD
WOOD is actually layers of XYLEM Heartwood: older xylem
in center of wood, that no longer conducts water
Darkens with age as it accumulates impurities
Sapwood: surrounds heartwood, active in transport
WOOD Growth Rings Indicate age of tree and
environmental conditions Thick rings indicate the
growing season experienced adequate moisture
Thin rings indicate there was less water (draught)
Wood Bark
Cork
Cork Cambium
Phloem
Vascular Cambium
Xylem: Sapwood
Xylem:HeartwoodContains old, nonfunctioningxylem that helpssupport the tree
Contains active xylem that transports water and minerals
Produces new xylem and phloem, which increase the width of the stem
Transports sugars produced by photosynthesis
Produces protective layer of cork
Contains old, nonfunctioning phloem that protects the tree
Section 23-4 LeavesDescribe how the structure of a leaf enables it to carry out photosynthesis
Describe how gas exchange takes place in a leaf
Leaf Structure Main organs of photosynthesis
Makes food for plants (glucose: C6H12O2)
Structure is optimized for absorbing light and carrying out photosynthesis Blades: thin, flattened to increase surface
area to absorb sunlight Attached to stem by petiole
Epidermis: outer layer Cuticle: waxy, protective layer
Protects tissues and limits water loss
Leaf Function Photosynthesis
Most of photosynthesis carried out in MESOPHYLL layer
Packed with chloroplasts Palisade Mesophyll: column-shaped cells just
under epidermis Absorb most of light coming into leaf
Leaf Function
Veins
Xylem
Phloem Vein
Cuticle
Epidermis
Palisademesophyll
Epidermis
Stoma
Guardcells
Spongymesophyll
Leaf Structure/Function
Spongy Mesophyll: loose tissue layer beneath palisade with air spaces between cells Air spaces connect with outside through
STOMATA
Leaf Structure/Function
STOMATA: pores in underside of leaf that let carbon dioxide and oxygen diffuse in and out of the leaf Each stoma consists of two GUARD CELLS
Guard Cells: cells in the epidermis that control the opening and closing of the stomata by responding to water pressure changes
Stomata/Guard Cells
Stoma Open Stoma Closed
Guard cells
Inner cell wall
Stoma
Guard cells
Inner cell wall
Leaf Structure/Function Gas Exchange
Leaves take in CO2 and give off O2 during photosynthesis Plant leaves allow gas exchange by opening their stomata
If kept open all the time, there would be large amounts of water loss due to transpiration
Plants keep stomata open just enough to allow photosynthesis to take place, not long enough to lose too much water
Guard cells regulate opening/closing of the stomata If water pressure is high, they open the stomata If water pressure is low, they close the stoma
Leaf Structure/Function
Veins
Xylem
Phloem Vein
Cuticle
Epidermis
Palisademesophyll
Epidermis
Stoma
Guardcells
Spongymesophyll
Section 22-5 Transport in PlantsExplain how water is transported throughout the plant
Describe how the products of photosynthesis are transported throughout the plant.
Water Transport Combo of root pressure, capillary action and
transpiration provides force to move water through the xylem Root Pressure: pressure created by water entering
the tissues of a root that pushes water upward in a plant stem
Capillary Action: tendency of water to rise in a THIN tube
Water is attracted to the walls of the tube and to other water molecules
Transpiration: loss of water through plant leaves by evaporation
When water is lost through transpiration the leaf “pulls” water upward from the roots
Moves water from HIGH to LOW pressure
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