Biology, Eighth Edition (Raven)

Chapter 38: Transport in Plants

Learning Outcomes

• Understand how water and minerals move upward through the xylem and how water balance keeps plants upright.
• Explain the roles of transpiration and “pushing” from water pressure in roots relative to water and mineral movement in the xylem. What are the roles of plasmodesmata and aquaporins?
• Describe the relationship between osmosis, energy, and water potential. What physical forces are involved in water potential? Relate root pressure to guttation.
• Explain the relationships among water potential, solute potential, and pressure potential.
• Explain the role of the endodermis and the Casparian strip. Why are root hairs usually turgid?
• Describe the factors that regulate the rate of transpiration. Include the following factors in your answer: epidermis, stomata, CO2, sun, K+, humidity, proton pumps, abscisic acid, water potential, light. What other factors are involved?
• Explain why some plants may die when their roots are submerged, that is, flooded, for long periods of time. What adaptations allow plants to live in fresh water? In salt water?
• Explain why phloem transport is considered a bidirectional process. What is phloem loading?
• What transport process is primarily responsible for transport in the phloem?