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
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
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.
secondary xylem = wood
Cohesion – Tension Theory of Water Movement
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
Pressure-flow hypothesis –