This series of posts will highlight the plants that help you celebrate the Yuletide season.
Never heard of these plants before? While the plants themselves may not be familiar, their hallmark products, frankincense and myrrh, are well known. These were two of the gifts presented to the baby Jesus by the three wise men, an event commemorated in Christian tradition on January 6 (Epiphany). Here’s more on the arboreal origins of these aromatic offerings.
Frankincense is derived from the Boswellia sacra or papyrifera trees, which are native to the Arabian Peninsula and Northeastern Africa. This small tree (~16 feet tall) seems to thrive in this harsh desert environment, often growing out of rocky mountainsides. It has papery bark that is easily shred and frankincense is collected by tapping the trees for their resin. A hole is made in the trunk of the tree causing liquid to drain from the wound. A couple of weeks later, the mostly-dried resin is collected for use as incense and perfume. Given their already harsh environment, Boswellia trees have a difficult life. The tapping process wounds the tree leaving convenient entry points for insects and other pathogens. One recent study suggested that the trees may decline by as much as 90% over the next 50 years. But frankincense has been an important trade commodity for the region for millennia, and increased demand is only partly to blame. Fire and browser grazing are also contributing to the decline of Boswellia trees. Scientists are working to salvage this economically and culturally important species. Researchers have detailed the 3D structure of the resin secretory system, and new insights on this anatomy should result in tapping techniques that provide higher yields with less damage to the trees.
Myrrh is another resin produced by the Commiphora myrrha tree in modern times, but the guidottii species is believed to be the source of myrrh brought by the Magi. Both of these trees share a native range with the Boswellia species. In addition to its scented resin, its trademark is its numerous spiny branches. It has sparse leaves, but the underbark of the main stem is green and photosynthetic.
In case you haven’t guessed the theme and plant biology word for the day, it’s resin. Sure, English usage could substitute sap, latex or gum, but each has distinct meanings when it comes to plants. In other words, not every substance bleeding out of a plant is the same thing. You may be most familiar with sap (maple syrup, anyone?). Sap is the liquid material transported in the xylem and phloem vasculature of plants. Latex (example: rubber latex) is a complex colloidal mixture of plant secondary metabolites produced in specialized laticifer cells. By the strictest definition, gum is derived from some internal breakdown of the plant’s cellulose that is exuded when the plant is wounded. They have high sugar content and are soluble in water. Resins have a complex chemical composition, but are primarily the oxidation products of the terpenoid essential oil metabolites. Resins are not water soluble. Amber is another example of a resin (remember that mosquito from Jurassic Park?). Both frankincense and myrrh are gum resins, meaning they are a mixture of both resin and gum.
Of course, there was a third gift brought to Jesus by the wise men- gold. Despite the rumors about turning straw into gold, we all know that gold is not a plant product.* However, a recent study found that Eucalyptus trees can be quite the miners. The roots of these trees can penetrate down as far as 130 feet deep in their search for water. When these trees are near gold ore deposits their efficient root vasculature siphons up microscopic gold particles that can be detected in their leaves. No one is suggesting razing Eucalyptus trees for gold, no matter what the going rate per ounce. Instead, mining exploration may be better served looking up at the leaves rather than underground for the mother lode.
OK, the last gift was a stretch for a plant connection, but-as the saying goes- two out of three ain’t bad. I hoped you enjoyed reading this series and exploring the biology behind some of our plant-related customs.
*It’s important to me that you know this. Remember, money doesn’t grow on trees. You can’t turn straw into gold. Maybe Rumplestiltskin taught that miller’s daughter, but the methods were never patented or properly documented on this side of fantasy.
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