by Jeff Lowenfels
Most books on growing plants contain an explanation of the soil Cation Exchange Capacity (CEC). This is one measurement of the ability of soil to hold nutrients. We’ve all seen the diagram: a root with positively charged hydrogen ions on its surface comes into contact with clay and organic particles that are covered with positively charged nutrient ions. The hydrogen ions swap places with the nutrient ions and the plant root gets its nutrients.
Unfortunately, the story almost always stops there. The root is in direct contact with one of the 17 nutrients needed, but what happens next? How do the nutrients get into the plant? Once they are inside the plant roots, how do they become part of the plant?
We all know how CEC works. The question is what happens next.
To figure out the answers for myself, I started writing Book Two of the Teaming series, soon to be published as Teaming With Nutrients: The Organic Gardener’s Guide to Plant Nutrition (aka what plants eat and what to feed them). As one would expect, it is a complex story and there is plenty of science involved, much of it recent as in “after you and I went to school.
Take a Look at the Cells
We all know that landscaping is half art and half science. Fortunately, most of us do quite well with the art half. It is the science part that is often missing. Once it is added, however, the results are almost always easier to obtain and the installation and maintenance always benefit, for the betterment of our customers.
What we learn when we look at how plants eat is a lot of cellular biology. Wow. This stuff is amazing! Start with the fact that an average size landscape tree has between 8 and 15 billion cells in it. This is a mind-boggling figure, even more so when you multiply the plantings. The resultant number of plant cells is so large that it is incredible that more of us don’t have a better understanding of how these cells actually work.
Each and every one of these billions of cells is connected to each other via passageways, literarily tunnels in their membranes. These plasmodesmata (the number in each cell depending on that cell’s function) provide a cytoplasmic stream from one cell to another. If you were small enough, it would be possible to travel from a root to the furthest leaf without ever passing through a cell membrane or cell wall.
Of course, you would have a difficult time making the journey. Getting into the cell is hard enough. You have to find the specific kind of protein tunnel to let you in, and, once inside, the explosions as energy is made and harnessed, the movement, the noise, the light, the webs connecting everything together, not to mention the vacuole and cellular vacuum cleaners would make it impossible to continue.
How Do You Get So Much from So Little?
Now, consider that a mere 17 elements are needed to sustain a plant. You can’t play a decent game with only 17 cards, yet 17 elements sustain the entire plant kingdom and the animal kingdom as well. How is this possible? How do 17 elements become the four molecules that make life: carbohydrates, proteins, lipids, and the all-important nucleic acids? And, even more amazingly, how do they make almost countless numbers of these molecules?
Each of these elements is combined by chemical reactions, and most of these reactions are a result of an encounter with an enzyme. A cell the size of the period at the end of this sentence can have 10,000 different kinds of enzymes and a thousand of each kind. In fact an incredible amount of a plant’s energy goes into making enzymes. Each of these enzymes is manufactured by plant cells just as is everything else that is part of that plant.
Cells, enzymes, and many of the 17 elements come to mind when planning or even planting a landscape, nonetheless appreciating one. Yet with just a little bit of exposure one can’t help but let the utter complexity and astonishing beauty of the simple cell and its activities add to the appreciation of what Landscapers do. After all, cells, enzymes, and only 17 elements are at the base of what makes every plant not only grow, but thrive.
Fortunately, the art of landscaping is already part science so things don’t usually break down and our plantings survive. Nevertheless, as more and more discoveries are made regarding how plants operate, it behooves us to stay informed and up to date. Not to do so would be a disservice to our customers and the profession. Even so, to fail to learn the science that goes with the art means you won’t fully appreciate the art. This is because there is a tremendous amount of wonderment that goes with the science.
About the Author
Jeff Lowenfels is the award-winning author of Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web. His next book, Teaming with Nutrients: The Organic Gardener’s Guide to Plant Nutrition, will be published in June. Jeff is the former president of the Garden Writers of America and a Garden Writer’s Fellow. He founded Plant a Row for the Hungry, a national program that encourages gardeners to dedicate one row in their gardens to feeding the hungry.
