Transcript Xylem_Phloem_Teacher_2 - DAVIS-DAIS

Vascular Tissue -- Xylem and
Phloem
Ground Tissue
-forms the bulk of the plant.
-thin-walled and
capable of
photosynthesis
when they
contain
chloroplasts.
-have thicker
walls for flexible
support (celery
strands).
-are hollow,
nonliving
support cells
with secondary
walls.
Plant Ground Tissues
• Thin cell wall
• Storage &
photosynthesis
PARENCHYMA
• Uneven cell wall
• Flexible support
COLLENCHYMA
• Thick cell wall
• Strength and
support
SCLERENCHYMA
Two Kinds of Plant Vascular Tissue
• Xylem - Carries H2O, dissolved nutrients.
- Upward movement.
- Dead at maturity.
- Vessel Elements- pitted
cell wall. Water pipeline
- Tracheids - pitted
• Phloem - Carries products of photosynthsis.-Sieve tube - perforated
- Up and downward movement.
end walls
- Alive at maturity
Sieve-tube
- transport sugar
Vessels
Tracheid
- Companion Cells- swirl
cytoplasm to push sugar
up or down
Companion
cells
Vascular Tissue
• Two types of vascular (transport) tissue:
• Xylem transports water and minerals from
roots to leaves and contains two types of
conducting cells: tracheids and vessel
elements.
• Phloem transports organic nutrients from
leaves to roots and has sieve-tube elements
with companion cells, sieve plates.
Xylem structure
Xylem transports
water and
minerals from
roots to leaves
Contains two
types of
conducting cells:
tracheids and
vessel elements.
Water
Leaves
Roots
Tracheids lie along side other tracheids, over-lapping
extensively, so that water can flow out of the pits of one cell
into an adjacent cell. This allows long range transfer of
water and solutes, although (since the cells are dead) the flow
has to be passive, pulled by an external force.
Water Flow (passive flow)
The driving force for this flow is hydrostatic pressure, coming
partly from root pressure (pushing up wards) but mainly from
the suction pressure created by water being evaporated from
leaves. Passive water flow in plants is upwards.
Softwoods (conifers) –
tracheids only
Hardwoods – note the
larger bore of the vessel
elements
In Angiosperms - Vessel elements, idealised
Vessel element, here with a open end (simple perforation plate).
A perforated
(scalariform)
perforation plate
Tracheids
Phloem structure
Transports
organic nutrients
from leaves to
roots
Has sieve-tube
elements with
companion cells
cells at sieve
plates.
Organic nutrients
Leaves
Roots