California State University Bakersfield
Welcome to the Webpage of
Dr. Anna L. Jacobsen
Plant Ecology and Evolutionary Biology
Dr. Jacobsen's Homepage Research Page
My research examines plant structure and function with a focus on the xylem of woody plants. The techniques and equipment that I use in my research are based on published methods and protocols, but most of these are necessarily altered and changed in the lab because they are custom systems that are not available in total from any single source or with any single set of instruction. This makes it difficult for students and researchers who are trying to adopt these techniques in their own labs and research. In the interest of working toward a methodological consensus, and the generation of reliable data as a scientific field, I am working to post detailed descriptions of the methods that I use. Although some researchers have recently reported having methodological problems with some alternative hydraulic techniques, the hydraulic techniques, methods, and equipment that I describe below and that I use in my lab have been thoroughly examined and tested. These tests, many of which have been published in peer-reviewed journals, have repeatedly shown that these methods produce reliable data on a wide range of species. For instance, see these recent publications:
Tobin MF, Pratt RB, Jacobsen AL, De Guzman M. 2013. Xylem vulnerability to cavitation can be accurately characterized in species with long vessels using a centrifuge method. Plant Biology 15: 496-504.
Jacobsen AL, Pratt RB. 2012. No evidence for an open vessel effect in centrifuge-based vulnerability curves of a long-vesselled liana (Vitis vinifera). New Phytologist 194: 982-990.
Sperry JS, Christman MA, Torres-Ruiz JM, Taneda H, Smith DD. 2012. Vulnerability curves by centrifugation: is there an open vessel artefact and are 'r' shaped curves necessarily invalid? Plant, Cell & Environment 35: 601-610.
Please email me if you notice something that is unclear or incorrect in any of these files. I would be happy to answer any questions that you have about these methods.
Plant Hydraulic Research Methods:
Methods for measuring hydraulic conductivity, xylem specific hydraulic conductivity, and leaf specific hydraulic conductivity:
Hydraulic conductivity apparatus
(posted 5/19/2011, updated 8/18/2011)
This file (pdf) contains a list of parts (with parts numbers) for assembling a system for measuring xylem hydraulic conductivity (Kh), as well as schematics, pictures of the system that we use in my lab, and additional notes about how to use the system. This file also contains details about how to measure and calculate xylem specific conductivity (Ks) and leaf specific conductivity (Kl).
Methods for flushing stem or root samples to measure maximum hydraulic conductivity:
This file (pdf) contains detailed notes and schematics on how to construct a system to flush stem or root samples to determine maximum Kh (Khmax or Kmax), including photos of our current system and notes on how to assemble and use the system. The way that our system is currently configured, the flushing apparatus connects to the hydraulic conductivity apparatus and they both use the same captive air tank and filter. Additional notes in this file discuss some of the pros and cons to the flushing of samples prior to vulnerability to cavitation curve construction and notes on the importance of the timing of sample collection. Cavitation fatigue is also briefly discussed.
Methods for the standard centrifuge-based construction of vulnerability to cavitation curves (measuring cavitation resistance and the water potential at 50% loss in hydraulic conductivity, P50):
Centrifuge methods and vulnerability curve methods
(posted 5/25/2011, updated 8/31/2012)
This file (pdf) contains photos and schematics that describe how the centrifuge works to generate negative pressures, how to calculate pressures that are generated with the centrifuge using sample length and rpm, and some additional notes about our rotor design and modifications and how we use our system to generate vulnerability to cavitation curves. We have found that this system, as we use it, is very reliable and produces vulnerability curves that match dehydration curves, even for long vesselled species that contain open vessels through a sample.
Plant Anatomy Research Methods:
Methods for determination of the vessel length distribution of stem or root samples using silicon injection and for determination of maximum vessel length using air-injection:
Vessel length methods
This file (pdf) contains detailed methods for both silicon-injection for mean vessel length and vessel length distribution determination and methods for air-injection for maximum vessel length determination.
Measuring vessel diameter, wall thickness, and (t/b)h2
Measuring percentage vessel, fiber and parenchyma area