BIOL 211 – CELLULAR AND ORGANISMAL BIOLOGY

Lecture Outline for April 8, 2005

Topic: transport in plants

Chapter 26 section 26.1 (focus on vascular tissue); Chapter 27 sections 27.3, 27.4

Figures used in lecture: 26.1, 26.6, 26.7, 26.8, 27.1, 27.6, 27.7, 27.8, 27.10

Additional Resources

Transport of Water and Minerals in plants (xylem)

Translocation in phloem – includes discussion of the Pressure-Flow Hypothesis

Transport within Plants

Define/explain: transpiration, cohesion-tension theory, surface tension, cohesion, adhesion, xylem, phloem, translocation, source, sink, pressure-flow hypothesis

You should be able to:

1. Describe the anatomy of plant vascular tissue including xylem and phloem, the function of each and the importance of a vascular system within plants.

2. Explain the cohesion-tension theory (transpiration-cohesion-tension theory) of water movement through xylem

3. Explain the pressure-flow hypothesis for the movement of sugars through phloem

Two types of vascular tissue

Xylem:

Phloem:

Water potential :

When no membrane is present, water moves from areas of high pressure to areas of low pressure.

Water Movement in Plants

Concentration gradients determine the direction of water flow.

Plants gain water from soil and lose it to the atmosphere.

Transpiration:.

Vascular Cambium:

secondary xylem = wood

Cohesion – Tension Theory of Water Movement

Transpiration:

Cohesion:

Tension:

Theory proposes that water is pulled up xylem by the surface tension generated at the interface between the atmosphere and water inside the leaf.

Translocation of Sugars in Plants

translocation:

Pressure-flow hypothesis –