Chpt37TransportinPlants - Chapter 37: HOW PLANTS TRANSPORT...

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Chapter 37: HOW PLANTS TRANSPORT THINGS The theme of this chapter focuses on TRANSPIRATION and TRANSLOCATION . This chapter is very straightforward and informative. Much information here tends to show up on standardized exams. Both the Concept Outline and Concept Review Outline are very helpful. Overview of the Details!!! Transport may be at the cellular level (from environment to cell); at the tissue level (from cell to cell); or, at the bulk flow level (from one organ to another – roots to leaves or vice-versa). Transport at the cellular level depends on the selective permeability of membranes and the role of the proton pump in providing the energy for such. The role of proton pumps in the transport process of plant cells is an application of the process of chemiosmosis . Read the discussion about chemiosmosis (P. 175) regarding the different methods of transport across membranes, including cotransport . Differences in water potential (megapascals) are important in moving water between plant cells (Fig. 37.2). Water potential is represented by the Greek letter Ψ ( Psi ). If a given plant cell has more solute in it with respect to the environment, water will move into the cell and cause the cell to become turgid . This swelling, called turgor pressure , is caused by the elasticity in the resistant cellulose cell wall resisting the water influx. When the wall pressure is great enough to offset the water influx (the water potential outside is now matched by the resistance of the cell wall) there is no more water influx (Fig. 37.4). The movement of water through cell membranes is enhanced/regulated by proteins called aquaporins (Fig. 37.3). This is a “hot” area of research in that we do not understand completely how these proteins regulate water uptake; i.e., turgor pressure is not the entire story! The issue of transport is even more complicated when one considers the role of the major compartments of
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This note was uploaded on 03/31/2008 for the course BIOL 1106 taught by Professor Georgesimmons during the Spring '08 term at Virginia Tech.

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Chpt37TransportinPlants - Chapter 37: HOW PLANTS TRANSPORT...

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