“Plant-Water Relations 1: Uptake and Transport” is the latest article in Teaching Tools in Plant Biology, and first of the in-depth series on the topic of Plant Physiology. It was written by me (Mary Williams), Mel Oliver of the USDA-ARS and Steve Pallardy of the University of Missouri.
This topic is a cornerstone of plant physiology, and also holds special significance today as we are seeing an increase in drought-induced plant death that is impacting forests worldwide. As Dixon and Joly pointed out in 1895, water movement in plants can be compared “to the action of a porous vessel drawing up a column of liquid to supply the evaporation loss at its surface”. Plants are much more complicated than clay pots on sticks, and the results of millionsof years of evolutionary selection underpin every step of the water-flow process. From the far ends of the roots to the highly sensitive guard cells, living plant cells sense and respond to water, allowing them to maximize CO2 uptake while minimizing dehydration injury and damage to their vulnerable conducting tissues. The rapid pace of climate change may be exceeding the ability of long-lived plants to adapt, leading to their hydraulic failure and death.
This Teaching Tool introduces plant-water relations through three entry points: the “first principles” that underscore the physiology of plants, the historical unfolding of our understanding, and the evolutionary origins of water conducting systems. Particular emphasis is placed on the roles of aquaporins in regulating hydraulic conductance, the structure and function of xylem in the efficiency and safety of the vascular system, and the influences of root and leaf anatomy on water transport. Students can test their understanding by examining Scholander and Tyree’s classic studies of mangroves, grapevines and maple trees, which face unusual challenges in water uptake and transport.
We encourage instructors to engage students inside and outside the classroom with questions for inquiry and discussion, such as those found in the Teaching Guide. For further inquiry, the Recommended Reading list includes current research and review articles as well as classic papers, all hyperlinked in the Lecture Notes and slides. If the time you have to teach this topic is very limited, the Abridged24 slide set summarizes the main points covered.
Look for Part 2, “How Plants Manage Water Deficit and Why It Matters” in early May 2014.
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