The Science and Spirituality of Trees

P1090816At the risk of sounding like a nineteenth century Romantic painter or poet, I feel that trees echo a part of the human spirit that otherwise remains silent in our day to day urban lives. Although their leaves exist to provide more surface area than what green branches alone would provide, trees assume a wide variety of hues in variable sunlight. Their matrices of lignin and cellulose form towering trunks spreading an intricate canopy over our view of the sky. From dawn to dusk, or from spring to autumn, the smells they evoke are not constant. With different wind speeds, a spectrum of rustling and swaying sounds are created. The symphony of colors, fragrances and sound waves of trees along with their imposing strength can interact with our memories and inner feelings. Although they are not of the intensity brought on by another human, trees evoke notes within us that no other living thing can replicate.

Existential issues aside, from the point of view of smaller organisms, a tree is in a sense its own forest. Over the ridges of the bark of some species, there are lichen—  algae and fungus, mutually helping each other* survive and serving as an indicator of pollution in cities. All tree-species provide niches and shelter for insects, birds and small mammals. Most trees would not survive if their roots were without the company of fungi known as mychorrhizas that help them absorb nutrients in exchange for carbohydrates.

And how they produce carbohydrates is a scientific wonder. Photosynthesis occurs in chloroplasts, structures which on a microscopic and evolutionary level reveal another partnership. A billion years ago, endosymbiosis, a process by which large cell engulfed smaller ones without killing them, led to the formation of plasmids. These evolved into the modern set of membranes and genetic material serving as the sites of photosynthesis in all plants.

The overall reaction of photosynthesis mocks what is actually occurring in the cells of trees: 6 CO2 + 6 H2O –> 6 O2 + C6H12O6 . Mix the reactants in vitro, and you would get nothing but carbonic acid! How does a tree or any plant manage to come up with a gas that is more often than not at the opposite end of the reaction arrow? How does it generate something sweet that flows through veins know as phloem, veins that the tree itself constructed from the same building blocks that it made with sunlight, with mychorrihizas’s transferred ions and the two official reagents water and carbon dioxide? Essentially through a network of cooperating cycles, chloroplasts absorb light frequencies in order to eject electrons from chlorophylls. These electrons are returned after they are ultimately taken away from water and transferred to molecules that use them to bond carbon dioxide. But the energy of the sun is not only invested in an electricity-like movement but in creating a voltage by temporarily isolating the hydrogen ions that also result when electron-yielding water splits into oxygen.

In the tropics there are at least 40 000 tree species but possibly more than 53 000. Temperate Europe, in contrast,  has only 124. Although forest cover has improved in Europe since the Middle Ages and has continued to do so recently, elsewhere on the planet areas with the most biodiversity have experienced the most loss. Here is a map showing which areas have done well and which haven’t between 1999 and 2012.mapping_world_trees

Landsat 7 data from 1999 through 2012 were obtained from a freely available archive at the United States Geological Survey’s center for Earth Resources Observation and Science (EROS).  More than 650,000 Landsat images were processed to derive the final characterization of forest extent and change.

From the vantage points of economics, carbon footprints and time management, it would make more sense for urban dwellers (now 54% of the planet) to access wooded areas as close to home as possible.

from National Geographic

In the United States, Pittsburgh, formerly known as the Steel City, has steadily reforested its surrounding hillsides, which had been previously cleared for logging and mining. Currently, this new growth forest along with four large parks occupy 42% of the urban area in Pittsburgh. Not only do the trees help filter pollution, avoid soil runoff in the sloped areas, they provide citizens a chance to have their spirits uplifted in an alternative way.

  • Postscript. Many biologists argue that the relationship only helps the fungus and not the algae. And yet some lichens show a three-way symbiosis involving a yeast. See  The previous reference gives no credit to Goward, a naturalist who first realized that a 3rd partner had to be involved in order to explain a mystery:  Bryoria fremontii, is hairlike, often brown and eaten by Northwestern indigenous peoples, but the lichen, Bryoria tortuosa,  is often yellow- green and toxic, with high levels of vulpinic acid. Yet both species had the same alga and fungus. It turned out that the toxic species had a lot more yeast.



Plant Chemistry Quiz

Unless they’re food on the table or part of captivating scenery, plants are under-appreciated. Even fewer people care for the intricacy of their biochemistry or realize how in tune they are with their environment. Here’s a short quiz written for nonspecialists who nevertheless have a curiosity for what goes on below the surface of leaves and flowers. Especially since there are no student grades at stake, if one can anesthetize the ego, one can trade in a little time for precious botanical knowledge. By clicking on “explanation” below each question, you will find the answer with more insight into the topic.

1.  Which of these compounds do plants assemble “from scratch”—- in other words just from water, carbon dioxide and ions from the soil?

(A) glucose

(B) amino acids

(C) flavonoids (used as a “sunscreen”, pigments and have many other functions)

(D) defence compounds

(E) all of the above

(F) none of the above


2. What compound, found in willow bark, can be reacted with acetic anhydride in the presence of mineral acid to make aspirin?

(A) paracetamol
(B) ibuprofen

(C) salicylic acid

(D) caffeine


3. Which of these plants, a member of the buttercup family, has one of the most poisonous roots due to 3 nasty alkaloids(aconitine, mesaconitine & jesaconitine)?

(A) monkshood (B) mountain ash

(C) opium poppy

(D) milkweed


4. Fermentation often occurs inside a cantaloupe. Small volumes of which alcohols are produced?

(A) butanol and ethanol

(B) ethanol and benzyl alcohol

(C) methanol and benzyl alcohol

(D) methanol and butanol



5. The glandular hairs of wormwood leaves, Artemisia annua , yields the important drug artemisinin? What disease does the drug treat?

(A) malaria (B) sleeping sickness

(C) elephantiasis

(D) ebola


6. At least 400 compounds contribute to its beautiful scent including these:

Which flower are we referring to? (look carefully at the structures!)

(A) iris

(B) peony

(C) rose

(D) violet


7. Compounds like tomatin make the leaves poisonous to many insects. Solanine makes the leaves of related plants also toxic to many insects. Compared to tomatin, solanine is considerably more toxic to humans. What plants are we referring to, respectively?

(A) tomatoes and red peppers

(B) tomatoes and potatoes/eggplant

(C) potaotes and red peppers

(D )potatoes or eggplant/ tomatoes


8. What common substance is crucial to photosynthesis because it is the ultimate source of electrons, which must be returned to excited chlorophyll?

(A) potash fertilizer

(B) nitrate fertilizer

(C) water

(D) carbon dioxide


9. Which plant’s roots provides sugars and leghemoglobin to bacteria in exchange for ammonium ion?

(A) bean

(B) radish

(C) tomato

(D) lettuce


10. What are the most common elements in a plant?

(A) N, C, H, O, P and Mn

(B) N, C, H, O and S

(C) C, H, O, N and Mg

(D) C, H, O, P, N and K


whitespace#Answer1 –E–Plants don’t eat. They only absorb water and ions from the soil and carbon dioxide from the air. With these substances they produce not only glucose but all of the amino acids, nucleic acids and secondary compounds that they require.

whitespace#Answer2 –C– The first two are tylenol and advil. Salicylic acid, upon reacting with acetic anhydride in the presence of a catalyst(acid), will create acetylsalicylic acid, which is aspirin.

Caffeine is an alkaloid, whose structure is unrelated to aspirin.

whitespace#Answer3 –A– If one is familiar with the buttercup family(Ranunculacae), one realizes from the shape of the leaves of the four plants shown, that only the monkshood is related to the buttercup. The opium poppy produces morphine in its pod. The fruits of the mountain ash in large amounts can cause stomach irritation and pain, vomiting, queasiness, diarrhea, kidney damage, and other side effects. Finally the milkweed concentrates its poison in the above ground parts.

whitespace#Answer4 –B– Technically an alcohol is any compound in which the oxygen atom is sandwiched between a hydrogen and a carbon atom from a hydrocarbon group. Cantaloupe produces small amounts of ethanol (CH3CH2OH), the same alcohol produced from fermentation of apples, hops and grapes to make cider, beer and wine. According to this source benzyl alcohol (C6H5CH2OH) can also be produced.  The latter is not at all toxic in low doses and has a sweet, pleasant odor. Not surprisingly, it is also found in hyacinth and jasmine flowers.

whitespace#Answer5 –A– Notice that malaria and one form of sleeping sickness are directly caused by protozoans(Plasmodium and Trypanosoma respectively), but in both cases the microorganism needs a vector, another organism that carries it from one victim to the next. Elephantiasis has no vector, and ebola is the only one out of the four above diseases to be caused by a virus.

From Center of Disease Control
From Center of Disease Control


For more on the use of artemesin and its “green” extraction, see this Periodic Table Video: artemisinin , which is sparingly produced by Artemisia annua and also difficult and expensive to artificially make from scratch.

whitespace#Answer6 –C– The name of the first compound gives it away, cis-rose

whitespace#Answer7 –B–
The name tomatin gives away the 1st part of the answer. Potatoes and eggplant leaves are toxic to humans becuase of solanine. Those of tomatoes are free of solanine and since tomato leaves have low concentrations of a much milder alkaloid, they are not toxic, contrary to popular belief. In fact tomatin is also found in green tomatoes.

whitespace#Answer8 –C–
Plants need water for a variety of reasons but especially to release electrons after sunlight ejects electrons from the photosystems of chloroplasts. Oxygen is produced when water dissociates, and the hydrogen ions that are also released set up a +/- gradient and thus a voltage that provides the chloroplast with the energy it needs to incorporate carbon dioxide.

whitespace#Answer9 –A–
From the list only the bean is a legume, which thanks to mutualism, can get ammonium ion from Rhizobium bacteria, which use nitrogen from the air to produce it.

whitespace#Answer10 –D– Along with N, C, H, O, and P,  sulfur is one of the six most common elements of life. Sulfur is part of four amino acids and is also key to many biochemical reactions. Having said that, S only makes up 0.1% of dry plant matter. From recalling the components of industrial fertilizer (N-P-K) one could correctly surmise that potassium(K) would be more common than sulfur in plants. And that would be correct. It makes just under 1% of plant dry matter, on average. Plants need potassium ion for proper transcription of many genes and to control the activity of many enzymes.

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