Gene expression and water transport in plants: A molecular introduction to plant physiology

Abstract

<p>“Gene expression and water transport in plants: A molecular introduction to plant physiology” is an introductory biology activity that helps students understand the relationship between cellular and molecular properties regulating plant physiology. This exercise combines diagram-based exercises with the interpretation of publicly available gene expression data from the Bio-Analytic Resource for Plant Biology (BAR) database.</p> <p><strong>Materials provided:</strong> The resource includes a student worksheet, a set of lecture slides to introduce and support the activity, as well as a step-by-step lesson plan for instructors including an answer key. This lesson has been implemented in an introductory biology course for life science majors and revised based on student and instructor feedback.</p> <p><strong>Target audience: </strong>The target audience for this activity is introductory biology students at the college or AP biology level. To get the most out of the activity students should be familiar with: osmosis and tonicity in cells; the roles played by membrane proteins, specifically ion channels; and the concept of gene expression. While the slides provided with the activity introduce the physiological concepts needed to carry out the activity, in our classroom this activity serves as a capstone to a brief plant physiology unit in which students have already been introduced to concepts such as water movement through plant vessels, various plant tissue types, and stomatal closure.</p> <p><strong>Time allocation:</strong> 50-75 minutes of class time. The activity has been completed in one 50-minute class period with a group of first-year undergraduates who had recently completed 100 min of lecture introducing plant anatomy and physiology. Part 1 and Part 2 are designed to be delivered together but could also be assigned as stand-alone activities.</p> <p><strong>Impact:</strong> This activity provides a process-oriented guided inquiry based learning exercise for the introductory biology classroom. It is designed to help instructors teach specific concepts in plant physiology while simultaneously reinforcing general biology concepts. Successful completion of the exercise will aid in integrating plant physiology into the greater introductory biology curriculum. Concepts covered that are specific to plant physiology include 1) water transport in roots and 2) stomatal aperture regulation by guard cells. General biology concepts emphasized include gene expression, membrane proteins, and osmosis.</p> <p><strong>Learning objectives:</strong></p> <ol> <li>Describe and compare the apoplastic, symplastic, and transmembrane pathways of water transport through plant roots, including the role of the Casparian strip in regulating water movement.</li> <li>Explain how ion transport and osmosis regulate guard cell turgor pressure and stomatal opening or closing in plants.</li> <li>Explain the role of stomata in regulating transpiration.</li> <li>Analyze cell-type specific gene expression patterns of membrane proteins and apply this information to hypothesize about their role in water transport or stomatal aperture regulation.</li> <li>Evaluate the role of differential gene expression in carrying out tissue or organ-specific physiological functions in plants and relate this to previous knowledge of animal physiology.</li> </ol>