My research interests include whole plant physiology and the long-distance transport of water by plants.  In particular, I am interested in how plants with radically different wood anatomy and growth forms coexist in the landscape.  What are the tradeoffs associated with coniferous, diffuse-porous and ring-porous wood types?  With trees versus vines?  Are the wider xylem vessels of ring-porous trees truly more hydraulically efficient on an entire-plant basis than the tracheids in a conifer? And if so, what constraints limit ring-porous trees’ ability to out compete conifer species?  Pursuing these types of questions has led me to study hydraulic characteristics, plant anatomy, and mechanics. 

As a postdoc with Drs. Barb Gartner and Rick Meinzer, I am using distal: proximal ratios of such characteristics as leaf specific hydraulic conductivity, conduit diameter, sap velocity, and conduit number to assess hydraulic efficiency.  By comparing the hydraulic efficiency, which we define as hydraulic conductance per investment in vascular volume, of trees and vines from temperate and tropical areas, we can determine potential tradeoffs associated with each habitat.

For my Ph.D. with Dr. John Sperry (University of Utah), I extended Murray’s law, which was derived for cardiovascular systems, to the xylem of plants.  Murray’s law predicts the conduit taper that maximizes hydraulic conductance per vascular tissue investment.  This solution occurs when the sum of the xylem conduit radii cubed (Sr³) is constant at every rank (i.e., the Sr³ in the trunk should equal the Sr³ of all 1yr-old branches combined).  Results showed that when the conduits were not providing the structural support of the plant, such as in compound leaves and young ring-porous wood, they complied with Murray’s law.  However, when conduits provided both mechanical support and water transport, as in conifer and diffuse-porous wood, the conduits deviated from Murray’s law. 

Publications:

McCulloh, K, and J Sperry.  In press.  Murray’s law and the mechanical architecture of plants.  For publication in Ecology and Biomechanics. CRC Press Inc., Boca Raton, FL, USA. 

McCulloh, K, and J Sperry.  In press. The evaluation of Murray’s law in Psilotum nudum (Psilotaceae), an analogue of ancestral vascular plants.  American Journal of Botany.

McCulloh, K, and J Sperry.  2005. Patterns in hydraulic architecture and their implications for transport efficiency. Tree Physiology. 25:257-267

McCulloh, K, J Sperry, and F Adler. 2004. Murray’s law and the hydraulic versus mechanical functioning of wood.  Functional Ecology.  18: 931-938

McCulloh, K. 2004. Do plants obey Murray’s law? Ph.D. Dissertation. University of Utah, Salt Lake City, Utah, USA.

McCulloh, K, J Sperry, and F Adler.  Water transport in plants obeys Murray’s law.  2003.  Nature.  421, 939-942.

           J.C. Domec

My current research interests include plant physiology and, the relationship of wood structure and anatomy to plant physiology.  To better understand the impacts of tree physiology on wood quality, my research focuses on how changes in wood properties (such as density, anatomical structure, strength) influence wood hydraulic performance.  I addressed how such changes affect water transport (and to a limited extent, mechanical properties).  Water flowing through the xylem of most plants from the roots to the leaves must pass through junctions where branches have developed from the main stem.  These junctions are studied as both flow constrictions and components of a hydraulic segmentation mechanism to protect the main axes of the plant.  The hydraulic nature of the branch and growth ring junction also affects the degree to which branches interact and can respond to changes in flow to other branches.

My future research goal is to understand the mechanisms by which species from related vascular plant groups (e.g., conifers vs. flowering plants) may move water under field condition or non-steady stage water transport.  Transient mechanisms to be tested in the laboratory include discrepancies between hydraulic conductivity parameters measured under steady and non-steady state flow for roots, trunks, and branches and their effect on the vulnerability to cavitation responses.  These data will be combined with measurements of vascular element dimensions, simple pit and bordered pit anatomy, direct corollaries of the water flux predictions.  Transient mechanisms to be tested in the field include capacitance phenomena (water storage ability) of the stem, and effect of non-steady driving force on whole tree hydraulics.

I came from the Royal Museum for Central Africa in Tervuren (Belgium) to join the team of Dr. Barb Lachenbruch and study the functional xylem anatomy. The topic of our joint project is “Microstructure of water paths in trees” and it is funded by the Marie Curie Outgoing International Fellowships program of the European Commission.
My current research focuses on the wood and bark structure in relation to permeability to gas and liquid. This knowledge is important for better utilization of wood products and for further development of the wood drying and preservation technologies. The outcome of the project will also contribute to the fundamental knowledge of tree anatomy and physiology. 

My expertise is in the anatomical analysis of wood structure and development. I have done research on the cambial activity and wood formation; cambium, wood and bark anatomy; morphogenesis of plants propagated in vitro and from cuttings through rooting or grafting. I am interested in methods for three-dimensional visualization of cell and tissue structure, such as optical sectioning by confocal microscopy or microcasting (corrosion casting) with SEM.  For microcasting, the woody tissue is perfused with a low-viscosity resin or plastic which fills cell lumens and all void spaces. Then, the resin is polymerized and the cell walls chemically digested and removed from the sample. What remains is a fine network of microcasts which when visualized by SEM reveal the three-dimensional structure of cell lumens and microcapillarities. For more information and microscopic images, visit here.

I have graduated from the University of Forestry in Sofia, Bulgaria and worked there as assistant professor of botany and wood anatomy. From 1995 until 2007, I was living in Japan where I did a Ph.D. at Hokkaido University and worked as a postdoc at the Forestry and Forest Products Research Institute in Tsukuba and in the Institute of Wood Technology at Akita Prefectural University (go to my CV).