“Lessons for Teaching in the Environment and Community” is a regular series that explores how teachers can gain the confidence to go into the world outside of their classrooms for a substantial piece of their curricula.

Part 12: Flirting with Danger

What happens when things seem to go wrong

by Jim Martin, CLEARING guest writer

n the last blog, I – and hopefully you – went out to snap off a twig from a cherry tree. I did that, except that the closest I have to a cherry tree is a prune tree, then began to examine it. Since I don’t have a lab now, I did the dissection with my tiny swiss army knife. The blade is a little over an inch long, and reasonably sharp after nearly 14 years of use. Here’s what I found.

The twig was dry and hard. When I cut it from the tree, I first cut off a piece about a foot long, then made another cut to create a six inch section of twig. I used the knife to slice a line around the circumference of the section about half an inch from one end. Then I cut lines perpendicular to the circumference line, about a quarter inch apart, around the section. After that, I used the edge of the blade to peel up sections of bark, one at a time.

Danger #1: When you look at illustrations of twigs and their parts, each section is shown intact, colored to set it apart from others, and often thicker than you find in the real thing. So, being mentally forewarned, I wasn’t discouraged when what I saw wasn’t what bark and cambium look like in the drawings in the book. The outside of the bark was easy to discern, but any cambium adhering to the inside was a little harder to decipher. After a section of bark was lifted, there was a relatively dark, thin layer which looked like it had been buttered on with a table knife. It wasn’t soft, but when I scraped it off, it was definitely different from the wood beneath.

So, that’s the cambium, a thin layer which can be scraped from the wood beneath the bark, and sometimes from the inner side of the bark itself. You don’t get a lot of it, but if it contains the enzymes we’re looking for, that convert starch to simple sugars, or simple sugars to starch, you don’t need a lot. If you have microscopes, you can examine it under their lenses. My job was to make a cambium preparation and add it to starch or simple sugars, and test for products. Here’s what I did.

I put the cambium into a small ceramic cup with a concave bottom, then added distilled water about one quarter inch deep. After that, I mashed the pieces of cambium to weaken cell walls and open cell membranes so the water could penetrate into the cells and expose their contents to whatever I added to the preparation. To start, I added a simple sugar, maltose, which I buy from time to time from a wine and beer making shop to use in some of my cake and icing recipes, to the cambium preparation.

First, I checked the maltose with iodine to make sure there was no starch in it. I mixed a little maltose with distilled water, swirled it around to distribute the maltose somewhat evenly, then added a drop of iodine. Then I mixed some more. All I could see was the brown iodine color. This told me that there was no starch present in the mixture. If there were, I’d see a dark blue-black color wherever there was starch. It’s very hard to mistake this particular reaction. So, the maltose had no starch.

Next, I tested a sample of the cambium solution with iodine. Most of the liquid and cambium were brown, but there were isolated points, little, scattered dots, of blue-black color. That means there was some starch present in the cambium. I made a note of how much I saw to compare with the results of adding maltose to the cambium.

Danger #2: Then, I added cambium to a fresh maltose solution, swirled it around, mixed it from time to time for about fifteen minutes, then tested it with iodine. Same results as for the cambium itself. I interpret this to mean that, if there was any maltose converted to starch, it couldn’t have been much. This result, which says I didn’t get what I expected, can be very intimidating. I had to keep a stiff upper lip!

I did the same with a starch suspension, testing with Clinistix, which I bought at the neighborhood drug store. (I chose this because I wanted to avoid the possible problems inherent in working with boiling water.) You just dip a stick into the solution, hold it thirty seconds, and compare the color at its tip with a chart on the container. Simple. The Clinistix told me there were no simple sugars in the starch.

Danger #3: The cambium solution was also negative, and when I added cambium to starch, the results were also negative. This means that no starch was converted to simple sugars by enzymes in the cambium. These are called negative results, and can bring you to tears. You’ve done all this work, and it amounted to nothing. But we still have to explain the negative results, and may learn a thing or two from doing it. They may not amount to nothing after all.

I took my sample of twig during the dead of winter. As I’ve mentioned before, I’m not a botanist. But, I know that plants take their life-cycle cues from their immediate, contemporary, environments. It’s winter, there are no leaves on the tree, the sun is low, daylight (photoperiod) is short, and I know that many trees store the sugars their leaves produce by converting them to the long-term storage molecules of starch and hold them underground, where it doesn’t get as cold as it does up in the branches of the tree. Then, when the sun’s elevation and the ultraviolet contents of the sunlight that reach the tree are just right, they generate chemical messengers which “wake” the plant up.

It might be that the prune tree in my yard is dormant, its cambium immobilized, and won’t convert starch or maltose to something else until it wakes up in spring. So, even if these results are negative, I don’t have to slink off into a corner to die. They are my evidence that the tree is dormant, and suggest to me to wait until May to try this again. In the meantime, I can look in the books for cambium, dormancy, and the effect of Spring’s sunlight on waking the cambium to do work. A veritable treasure trove from a set of results which might have been discouraging.

Danger #4: You have to learn to flirt with danger. Here’s another lesson embedded in this adventure. If I hadn’t done this sort of thing before, I might have believed I hadn’t done the tests correctly. Being sort of prudent, I did repeat each test. I’m human, and prone to error. From my perspective, the second set of results confirmed the first, and I knew I had to acknowledge them and look further for explanations. It’s an easy trap to fall into: You don’t get the results you expect, so you do the test over and over and over again. Have confidence that, if you’ve followed the test procedure carefully, you can trust the results. Your job is to find what they have confirmed.

(An anecdote: One year, a chemist from a regional organization was working with a team of elementary and middle school teachers, training them to do environmental sampling. They were in a place where the water was cold and running over rocks. It was also covered by vegetation. They were getting very high results for dissolved oxygen, and the chemist assumed they weren’t doing the test correctly because the vegetation blocked the sunlight that helps plants produce oxygen. They repeated their tests for a long time, then decided there was something wrong with the chemicals. Cold water, running over rocks, should have high concentrations of dissolved oxygen. So, a professional chemist lost perspective, and missed an opportunity to use clearly repeated results to explain. If a pro can do it, we can too. But keep it to a minimum. You have a brain, and it does work, if you let it. If you’ve checked your procedures, then the most reasonable explanation is that they are telling you what’s actually there.)

For the time being, I’ve put my cut stems in water and will see what they look like in spring. I’ll also repeat this activity then. In May, I may wish I’d done a test in Fall! And, I’ll find out what I can as I wait. Never give up the ship.

This is the twelfth installment of “Teaching in the Environment,” a new, regular feature by CLEARING “master teacher” Jim Martin that explores how environmental educators can help classroom teachers get away from the pressure to teach to the standardized tests,  and how teachers can gain the confidence to go into the world outside of their classrooms for a substantial piece of their curricula. See the other installments here, or search Categories for “Jim Martin.”