Vascular Tissue -- Xylem and Phloem

Ground Tissue

-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.

-forms the bulk of the plant.

SCLERENCHYMACOLLENCHYMA

• Thin cell wall

• Storage & photosynthesis

• Uneven cell wall

• Flexible support

• Thick cell wall

• Strength and support

PARENCHYMA

Plant Ground Tissues

Two Kinds of Plant Vascular Tissue• Xylem

• Phloem

- Upward movement.

- Dead at maturity.

- Carries H2O, dissolved nutrients.

- Carries products of photosynthsis.- Up and downward movement.- Alive at maturity

- Vessel Elements- pitted cell wall. Water pipeline

- Tracheids - pitted

-Sieve tube - perforated end walls

- transport sugar

- Companion Cells- swirl cytoplasm to push sugar up or down

Vessels Tracheids

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Companion cells

Vascular TissueVascular 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 structureXylem structure

Xylem transports water and minerals from roots to leaves

Contains two types of conducting cells: tracheids and vessel elements.

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Roots

Leaves

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

Vessel element, here with a open end (simple perforation plate).

Tracheids

A perforated (scalariform) perforation plate

In Angiosperms - Vessel elements, idealised

Phloem structurePhloem structure

Transports organic nutrients from leaves to roots

Has sieve-tube elements with companion cells

cells at sieve plates.

Leaves

Roots

Org

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