Vascular Tissue -- Xylem and Phloem

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Vascular Tissue -- Xylem and Phloem
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Ground Tissue
-forms the bulk of the plant.
-are hollow, nonliving support cells with
secondary walls.
-thin-walled and capable of photosynthesis when
they contain chloroplasts.
-have thicker walls for flexible support (celery
strands).
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Plant Ground Tissues

• Thick cell wall
• Strength and support

• Thin cell wall
• Storage photosynthesis

• Uneven cell wall
• Flexible support

COLLENCHYMA
PARENCHYMA
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Two Kinds of Plant Vascular Tissue
- Vessel Elements- pitted cell wall. Water
pipeline - Tracheids - pitted
- Carries H2O, dissolved nutrients.

• Xylem
• Phloem

- Upward movement.
- Dead at maturity.
- Carries products of photosynthsis.

• Sieve tube - perforated end walls
• - transport sugar
• - Companion Cells- swirl cytoplasm to push sugar
  up or down

- Up and downward movement.
- Alive at maturity
Sieve-tube
Companion cells
Vessels
Tracheids
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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.

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Xylem structure
Leaves
Xylem transports water and minerals from roots to
leaves Contains two types of conducting cells
tracheids and vessel elements.
Water
Roots
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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.
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Softwoods (conifers) tracheids only
Hardwoods note the larger bore of the vessel
elements
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In Angiosperms - Vessel elements, idealised
Vessel element, here with a open end (simple
perforation plate).
A perforated (scalariform) perforation plate
Tracheids
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Phloem structure
Transports organic nutrients from leaves to roots
Has sieve-tube elements with companion
cells cells at sieve plates.
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