Hi, are you aware of any anatomical differences between woods of stem and root?
Usually cell walls are thinner, root lacks pith, etc. But you should compare the stem and root wood anatomy of a particular species to see the differences.
This two articles could probably help you:
Bernabei, M., & Bontadi, J. (2011). Distinguishing root- and stem-wood of Picea abies. IAWA Journal, 32(3), 375–382.
Ranjani, K., & Krishnamurti, K. V. (1987). A comparative study of root and stem woods of some members of the Mimosoideae (Leguminosae). Journal of the Arnold Arboretum, 68, 349–355.
Hello Wang Bingrui, thank you for you answer. Would you have any information to share with us concerning these anatomical differences?
Thank you very much for your answers. I know differences between stems and roots in primary tissues organization. I'm more curious about differences concerning Xylem II.
Francis Halle (1999; Ecology of reiteration in tropical trees) suggested that wood could be originated from roots. Looking at the morphology of trees, one can find trees with aerial roots completely separated from the trunk (for example some fig trees), roots that merge with each other to make a structure analogous to a trunk in hemiepiphytes, root veins visible at the trunk surface and originated at the base of big structural branches. From these observations, he made the hypothesis that the wood of the trunk is constructed from an aggregation of root systems. Under this hypothesis, the anatomy of wood (Xylem II) should be identical in stems and roots.
I have found a good example of a tree that became a stem as the soil washed out. However a root is more exposed to pulling forces, it looks to me that this 'root-turnd-into-a-stem' is able to take the weigth of at least a part of the tree, thus performing the physical properties of a stem. This example is a braodleaved tree (a beech as I remember). I have also an exemple of a pine tree on the same location showing the same phenomena.
This pine tree also supports the idea that stems can originate from roots.
Usually cell walls are thinner, root lacks pith, etc. But you should compare the stem and root wood anatomy of a particular species to see the differences.
This two articles could probably help you:
Bernabei, M., & Bontadi, J. (2011). Distinguishing root- and stem-wood of Picea abies. IAWA Journal, 32(3), 375–382.
Ranjani, K., & Krishnamurti, K. V. (1987). A comparative study of root and stem woods of some members of the Mimosoideae (Leguminosae). Journal of the Arnold Arboretum, 68, 349–355.
I remember the excellent work by Cornelia Krause back in the 90ies at Hamburg University (Krause C. 1992. Ganzbaumanalyse von Eiche, Kiefer und Fichte mit dendroökologischen Methoden. Dissertation Uni Hamburg). She also published a number of papers...see links. cheers...
http://www.nrcresearchpress.com/doi/abs/10.1139/x99-138
http://aob.oxfordjournals.org/content/102/5/667.short
http://pubs.cif-ifc.org/doi/abs/10.5558/tfc71747-6
Thank you all for your answers! So far, I didn't manage to find any qualitative differences, only quantitative variations. I'm convinced that comparing different positions in the canopy (base of the trunk, top of the trunk, branches, twigs) would also disclose numerous quantitative differences. Let me know if you find any criterion that would allow to formally identifying a cube of wood (without primary tissues) as being issued from root or from stem.
Hello Tristan,
I am not so sure that we could believe in a qualitative criterion to distinguish between twigs, trunk or roots ... What i am sure is that generally basic specific gravity varies between branches and trunk. In some species basic specific gravity in trunk is higher than in branches, the inverse pattern is also possible. Since basic specific gravity is highly correlated with cell wall thickness, you might distinguish, or at least have an idea about the position of your cube in the tree. But this is relative and specific to a particular species. Another interesting quantitative criterion is vessel length and vessel lumina diameter. Generally in branches vessels are shorter and narrower than in trunk .. You can have a look to the xylem chapter in the last edition of the book "Esau Plant Anatomy", in which you can read more about these kinds of considerations that can guide you to others specific references. Hopping to talk with you soon about this !
Dear Tristan, how are you?
Anatomically, we can distinguish stem from root using the maturation direction of the primary xylem which is still present even during the secondary growth. During the primary growth in stems, the xylem has its first tracheary elements (protoxylem) located internally of the vascular cylinder and the subsequent maturation (into metaxylem) occurs in a centrifugal way. In roots, the opposite occurs, the first tracheary elements (protoxylem) are located in the outer portion of the vascular cylinder, and its differentiation (into metaxylem) occurs towards the center, or in a centripetal way. Thus, the xylem in stems is called endarch (with centrifugal maturation of the tracheary elements), and, in roots, it is called exarch (with centripetal maturation of tracheary elements).
Hope it helped a little bit.
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