Excerpts from Jim Conrad's
Naturalist Newsletter

from the February 20, 2011 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá ruins, central Yucatán, MÉXICO

Walking through Pisté I pass a large Cedro tree, Cedrela odorata, a species we've already profiled at http://www.backyardnature.net/n/w/cedro.htm.

The tree in Pisté caught my attention because its trunk had been wounded, and from the wounds copious quantities of resin had issued, congealing into amber-colored, semi-hardened masses the consistency of hard, waxy cheese. You can see all this at shown below:

Resin on wounded Cedro tree, Cedrella odorata

Why do certain trees, such as pines, Araucarias and our Cedros, issue resin when wounded, while most trees don't, at least not in noticeable quantities?

Chemically, resins consist mostly of hydrocarbon waste products -- waste from the plants' biological processes such as respiration, photosynthesis, glycolysis, and the like. For this reason it's sometimes resin is seen as little more than an incidental, unavoidable byproduct of life, like feces among animals.

However, sometimes resin definitely helps plants they exude from. They may contain compounds that repel, confuse or kill a wide range of plant-eating invertebrate animals, especially insects, and disease organisms. Also compounds that evaporate from the drying resin -- volatile phenolic compounds -- have been documented attracting organisms that parasitize or prey upon herbivores that attack the plant.

In the special case of our Cedro tree an especially aromatic resin suffuses the tree's heartwood famously repelling insects and bestowing the wood with an intense odor like that of northern cedars and junipers. Our Cedros are not closely related to cedars and junipers, however, Cedros being angiosperms and cedars and junipers being gymnosperms.