California State University Bakersfield

 

Welcome to the Webpage of

Dr. Anna L. Jacobsen

 

Plant Ecology and Evolutionary Biology

Plant Structure-Function

Research Methods

Dr Anna Jacobsen collecting stems in the field 

Dr. Jacobsen's Homepage    Jacobsen Lab Research Page    Jacobsen Lab Publications

 

My research examines plant structure and function with a focus on the xylem of woody plants and how plants respond to water stress and drought. 

The techniques and equipment that I use in my research are based on published methods and protocols, but because the equipment needed to conduct these measures must be custom built and is not available in total from any single source or with any single set of instruction, it is sometimes difficult for students and researchers who are trying to adopt these techniques.  In the interest of assisting those who are interested in incorporating some of these methods into their own research, I am working to post detailed descriptions of the parts, models, construction of, and use of these techniques and equipment. 

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 have repeatedly shown that these methods produce reliable data on a wide range of species.  For more information about these tests, see these recent publications:

Hacke UG, Venturas MD, MacKinnon ED, Jacobsen AL, Sperry JS, Pratt RB. 2014. The standard centrifuge method accurately measures vulnerability to cavitation curves of long-vesselled olive stems. New Phytologist, doi: 10.1111/nph.13017

Jacobsen AL, Pratt RB, Davis SD, Tobin MF. 2014. Geographic and seasonal variation in chaparral vulnerability to cavitation. Madroņo 61: 317-327

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.

Additional publications and references are included in the method-specific pdfs listed below.

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 the air-injection of single vessels to determine the air-seeding pressure distribution of vessels within samples

Single vessel air-injection

Contributed by Dr. Martin Venturas

(coming soon)

This file (pdf) contains a list of parts (with parts numbers) for assembling a system for measuring the air-seeding pressure  of individual vessels.  These data may be compiled to develop a vulnerability distribution for vessels.

 

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, updated 8/27/2014)

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:

Flushing apparatus

(posted 5/24/2011, updated 8/27/2014)

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:

Silicon-injection vessel length distribution methods

(posted 8/19/2011; updated 8/20/2014)

This file (pdf) contains detailed methods for using silicon-injection to determine mean vessel length and the vessel length distribution of stem or root samples.

 

Methods for determination of maximum vessel length using air-injection:

Air-injection vessel length methods

(posted 8/20/2014)

This file (pdf) contains detailed methods for using air-injection to estimate the maximum vessel length of stem or root samples.   

 

Methods for staining to determine active xylem area, sapwood area, and/or to identify hydraulically active (i.e. conductive) vessels:

Active xylem staining methods

(posted 8/27/2014)

This file (pdf) contains detailed methods for mixing and filtering a crystal violet dye solution and using this dye solution to stain stem or root samples in order to identify the active xylem area, sapwood area, or hydraulically active vessels found within these sections.     

 

 

Measuring vessel diameter, wall thickness, and (t/b)h2

(coming soon)

 

 

Measuring percentage vessel, fiber and parenchyma area

(coming soon)

 

Dr Anna Jacobsen in the field at Red Rock Canyon CA Dr Anna Jacobsen setting up equipment in South Africa