Speaking of Nature: One potato, two potato: even part of a potato can yield more

  • The trout lily is one of our beautiful spring wildflowers. Their roots survive the winter underground and the plant’s growth will be fueled by starches that are stored in little bulbs that resemble potatoes. For The Recorder/Bill Danielson

  • This chestnut oak acorn is loaded with starch to provide energy for the embryonic tree hiding within. For The Recorder/Bill Danielson

  • Bill Danielson

For The Recorder
Sunday, October 08, 2017

Happy Columbus Day everyone! This particular observance comes a little earlier in the month than usual, and a look outside will show just the beginnings of the splendor of the fall foliage season that we enjoy every year. With a particularly wet July and an oddly dry August and September, it is difficult to predict the quality of the colors we may see, but I am sure they will be spectacular, all the same.

The topic for today’s column is starch. This may seem more than a little odd, but stick with me for a moment and I hope you’ll see the connection. Remembering that the natural world is full of rhythms — the changing seasons and the responses of our wild plants and animals to those changes — will help you to feel the rhythms in the human world as well. September is “back to school” season. We also start to see football games on TV, and we may also begin to look forward to upcoming holidays, like Columbus Day.

In the world of education, there is also a distinct and unmistakable rhythm. In biology, we always start the year with the scientific method, then move on to the concepts of atoms, ions and isotopes. Then, inevitably, we move onto the more complex topics of molecules and organic compounds. It was in this particular section that I had a great conversation with one of my classes last week. We were talking about carbohydrates, and one of my students asked a question about potatoes. Basically, the question went something like this: If a potato is a potato then how can you get more potatoes?

It turns out that the students that asked the question was aware that a potato is a type of plant, but she was completely unaware that potatoes are flowering plants that produce seeds.It was also apparent that the students in the room, in general, didn’t understand how plants capture energy and store it for later use, so this was the perfect opportunity to talk about starch.

In the world of organic compounds, there are four main varieties: carbohydrates, proteins, lipids and nucleic acids. Each group has particular characteristics that make it important for life. Carbohydrates are basically energy currency in living things. Plants can build sugar molecules through the process of photosynthesis, which collects the energy of sunlight and stores that energy in the covalent bonds of glucose. This energy can remain safely locked up in the sugar molecules and then released at a later date when the energy is needed.

The world of carbohydrates is really just an elaborate array of different recipes for storing sugar. One of the simplest recipes is that of glucose. Six carbons, 12 hydrogens and six oxygens woven into a hexagonal molecule called a monosaccharide (a fancy way of saying a single sugar). Slightly more complicated is a sugar called sucrose. You may know this particular compound as the white crystalline substance that you add to your morning coffee.

Sucrose is formed by combining the monosaccharide glucose and another monosaccharide called fructose. Join them in just the right way and you get a double sugar (a disaccharide). This particular game can be played with all sorts of different combinations of sugars, but the molecule that is designed for long-term energy storage is starch.

Starch is what is known as a polysaccharide, which basically means that it is a molecule made up of many sugars. The sugars are all glucose molecules that are simply linked and repeated over and over. This makes the glucose molecules “monomers” and the larger starch molecules “polymers.” Think of a metal chain and you will have the right idea in your head. Each link is a glucose monomer and the entire chain is the starch polymer. You can even grab a pair of pliers and pop the links apart, which is the basic image you need to understand the beginnings of digesting food.

Anyway, plants are experts at collecting and storing energy and starch molecules are an integral part of plant survival and reproduction. A potato is a special energy-storage root known as a “tuber.” Safe from the elements underground, the potato can survive the winter then provide energy for a burst of vegetative growth the following spring. Commercial potatoes are propagated in this manner. A single potato can be split and replanted and the “eyes” will grow into potato plants. The plants then spend the warm moths collecting and storing energy in the form of new potatoes. So, one potato (or even part of one potato) can yield many more.

Starch is also found in plant seeds, which are basically little suspended animation pods for plant embryos. The best way to see this for yourself is to find a peanut in the shell, open it and then carefully separate the two halves of the peanut. If you examine the ends of the two halves, you will inevitably find that on one there is a sharp little point. Look closely at this object and you will see that it is in fact a tiny little plant with leaves and everything.

The portion of the peanut that we are interested in eating is a structure known as a cotyledon. In a peanut, there are two cotyledons and they are basically the entire resource pack that an embryonic plant can draw upon for its development. The parallel in the animal world is an egg. The egg yolk and albumin contain all of the energy and resources that an embryonic animal needs to get started.

Well, the magic of seeds is that some of them can remain dormant, but viable for years. As soon as our distant ancestors realized this, it set the stage for human civilization. By intentionally cultivating certain plants (rice, wheat, oats, corn, rye, millet, etc.), harvesting the grain and then storing it for leaner times, humans allowed themselves to shift from a nomadic, hunter-gathering lifestyle to a lifestyle anchored to permanent settlements. And once people “settled down,” they could afford to take the time to develop technologies and focus on science.

The most amazing thing about starch is that it can be stored for years, even decades, without going bad. Take some of the seeds that you harvested, grind them up and, voila!, you have flour. You have destroyed the seed, which means you can no longer grow another wheat plant, but you have a stable product that can be stored and used to make all sorts of delicious and nutritious products. The only trick is that the little embryonic wheat plant has to be removed first.

Clever humans have marketed these plants by roasting them and putting them in jars. The coarse, granular material is known as wheat germ.

Our woodlands are filled with plants that are preparing to use starch in all sorts of interesting ways. Some of our most beautiful spring wildflowers, like trout lilies, blue-bead lilies, blood roots and trilliums are bulb plants that store energy in specialized roots, not unlike those found on potatoes. These plants have already done their thing for the year and are already “hibernating” and waiting for next spring.

Other plants, like oak trees, are sending their offspring into the world in those little life support systems we know as acorns. Like peanuts or wheat seeds, acorns are almost entirely comprised of starchy food resources for the embryonic plants hidden within. White-tailed deer fatten up on acorns and chipmunks and squirrels will amass huge collections of acorns to see them through the winter. Those acorns that aren’t consumed, will germinate and grow into new trees next year, which was the only motivation of the oak trees in the first place.

Today is a holiday, and I hope the weather is nice enough for you to go for a walk in the woods. If this is something you get to do, keep the notion of carbohydrates and starches active in the back of your mind. Humans have come a long way since we learned to store food for the winter, but our wild plants and animals have been doing it for millions of years.

Bill Danielson has worked for the National Park Service, the US Forest Service, and the Massachusetts State Parks. He has been a professional writer and nature photographer for 19 years and he also teaches high school biology and physics. Visit www.speakingofnature.com for more information, or go to Speaking of Nature on Facebook.