viii: The Chemistry Column
Ancient memory Claire Gormley There is a tree in my neighbourhood that I love to walk by. Its bark is a soft grey, and its sturdy trunk twists at the base as if it is turning its neck to look behind. Whenever I see it I always wonder what might have happened to make it grow in such a unique way. What story could this tree share? As a society, we revere our elders for the experiences they lived through and the precious memories they hold. This is one of the reasons why dementia is so devastating, not only for those living with the disease, and their families and carers who also suffer, but for society as a whole. While we may make an effort to save our elders’ stories so they can be appreciated by future generations, seldom do we extend the same appreciation for the ancient memory of the steady giants that tower overhead. Every year trees mark down their experiences in the form of tree rings. Dendrochronology is the study of tree rings, and has applications across a variety of fields including archaeology and climate science. Through taking core samples of trees and studying the ringed patterns, dendrochronologists can determine the tree’s age and the various environmental conditions it has experienced over time. Currently the oldest living tree known to humankind— an unnamed member of Pinus
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longaeva or Bristlecone Pine —has been cross-dated by scientists to be 5,070 years old as of 2020 (Guinness World Records). An ancient Bristlecone Pine family located in the White Mountains of California is widely accepted to be the oldest non-clonal species of tree, with many members sampled being over 4,000 years old and still growing (USDA Forest Service). These trees sprouted around the time the foundations of Ancient Egyptian society were being developed– between 3100 and 2686 B.C. The process of tree ring formation is not well understood, but it is of growing importance due to the implications it may have for carbon sequestration and climate action (Rathgerber, Cuny & Fonti, 2016). Initially, scientists thought that the amount of carbon that can be sequestered into wood is limited by how much photosynthesis a plant can do; however, there is the suggestion that xylem formation could play a more significant role (ibid). Xylem is a tissue responsible for transporting water and nutrients from the roots to the leaves of vascular plants; xylogenesis is the process of producing and differentiating new xylem cells in functional wood cells. The process involves five steps: division of a cambial mother cell; enlargement of newly formed daughter cells; deposition of the secondary cell wall;
