WEEK 8: WATER UPTAKE, WATER TRANSPORT & TRANSLOCATION

What does xylem transport?

Water and mineral salts from the roots to the aerial parts of the plant.

What process is associated with movement of materials through xylem?

Transpiration.

Where is xylem located in the vascular bundle?

In the inner portion or centre.

What cells make up xylem?

Vessel elements and tracheids.

What is special about xylem vessels?

Their walls consist of fused cells forming a continuous tube for unobstructed water flow.

What is the state of xylem vessels at maturity?

They are dead, hollow and contain no cell contents.

What does phloem transport?

Food and nutrients to storage organs and growing parts of the plant.

What type of transport occurs in phloem?

Active translocation.

What does bidirectional transport mean?

Transport can occur up and down the plant depending on the source and sink.

Where is phloem located in the vascular bundle?

In the outer portion.

What cells make up phloem?

Sieve tube elements and companion cells.

What are sieve plates?

Porous cross walls formed where sieve tube cells connect at their transverse ends.

Are phloem tissues living?

Yes, although sieve tube elements lack nuclei and have few organelles.

How do minerals enter the xylem?

Minerals are actively transported into the xylem vessels.

What effect does mineral uptake have on water potential in the xylem?

It lowers the water potential.

How does water enter the xylem?

Water flows into the xylem by osmosis.

What is root pressure?

Pressure produced in the roots that pushes some water upwards through the xylem.

What causes transpiration pull?

Water evaporating from the leaf creates tension/low hydrostatic pressure, pulling water upwards through the xylem.

What is cohesion?

The attraction between water molecules.

Why is cohesion important in water transport?

It creates a continuous column of water that can be pulled upwards through the xylem.

What is adhesion?

The attraction between water molecules and the walls of the xylem.

What is capillary action?

The upward movement of water caused by adhesion to xylem walls and cohesion between water molecules.

What is capillarity?

The movement of water upwards through narrow spaces due to adhesion and cohesion.

What happens when water evaporates from the leaf?

Water is lost through transpiration, creating tension that helps pull water upwards through the xylem.

What is translocation?

The movement of organic compounds such as sugars and amino acids from sources to sinks.

What is a source?

The place where organic compounds are synthesised, mainly the photosynthetic tissues such as leaves.

What is a sink?

A place where organic compounds are delivered for use or storage, such as roots, fruits and seeds.

Which tissue transports organic compounds from sources to sinks?

Phloem.

In what form are sugars principally transported?

As sucrose.

Why is sucrose suitable for transport?

It is soluble but metabolically inert.

What is plant sap?

The nutrient-rich, viscous fluid of the phloem.

What is the difference between transportation and translocation?

Transportation through xylem moves water and mineral salts mainly upward, while translocation through phloem moves manufactured food/organic compounds from sources to sinks and can occur in both directions.