Managing Energy Like a Tree
Paul Kando
A sugar maple has about 500 pounds of green leaves with a surface area of several hundred square feet. It produces roughly 2 metric tons of sugar each year, with no externalities and zero waste. How so?
photo credit: Topher Belknap
An important molecule in all living things is ATP (short for Adenosine Triphosphate). It is composed of a nitrogenous base, adenine, a 5-carbon sugar and 3 phosphate groups. The phosphates have a negative charge, and like charges — 2 negatives — repel each other. To overcome this repellant force there is a strong bond between 2 phosphates. However the third phosphate makes ATP into an unstable molecule, held together by externally supplied energy. Withdraw that energy and the third phosphate breaks off, leaving a 2 phosphate molecule, ADP (for Adenosine Diphosphate). Add energy to ADP and the third phosphate will reattach, creating ATP again. Thus ATP is good for storing energy or transferring it between molecules. It is the “energy currency” of the cell, which allows energy to be changed into a form useful in lots of ways within the organism.
Two basic processes that involve energy in a cell are photosynthesis, which brings new (solar) energy into the eco-system, and aerobic respiration, which makes that energy available for the work of living.
In photosynthesis 6 carbon dioxide (CO2) molecules plus 6 water (H2O) molecules plus energy in the form sunlight combine into the sugar glucose (C6H12O6) with 6 oxygen (O2) molecules released. Aerobic respiration reverses this reaction. Animals breathe in the 6 oxygens and break down the glucose, producing 6 carbon dioxides, 6 waters, and energy, now stored in the form of ATP and available for use for the functions of life. These two processes are near mirror images of each other.
So our sugar maple grabs energy from the sun and stores it the chemical bonds of glucose, releasing some oxygen into the air. During aerobic respiration, using oxygen from the air, that glucose is ripped apart, releasing the original carbon dioxide and water, and storing, in ATP, energy for the organism’s own use. Nothing is wasted: nature recycles everything.
But what makes the tree grow? The energy captured by photosynthesis plus various nutrients dissolved in the water used in photosynthesis. Those nutrients are made available to the tree by collaborating organisms. Nutrients like nitrogen, phosphorus are produced by microorganisms in the soil, largely from the recycled remains of living things and their metabolism. And in a collaborative arrangement, like most vascular plants, our tree maintains a symbiotic association between its own roots and the mycelium (the thread-like vegetative part) of a fungus. The fungus assists in the absorption of minerals and water from the soil and defends the roots from other fungi and nematodes, while the plant provides carbohydrates to the fungus.
Isn‘t this a great model to emulate? Decentralized (cell level/ local level) management — no hierarchy. Zero waste – everything is reused. Collaboration – dare I say democracy? Could trees be smarter than we are?