Are You Thankful for Green Plants?
PERHAPS you are not very fond of plants and not particularly interested in them. However, even if botany bores you, there is good reason for you to be thankful for green plants.
Why, even a die-hard city dweller knows that green plants are just the thing to make a dingy office or apartment look livable. And when temperatures soar, the urbanite is delighted to sit under the shade of a tree, even if he has to fight for a patch of green in a congested park.
Out in the country, though, you can really appreciate the splendor of earth’s greenery. It decorates the world we live in like an exquisitely designed carpet. Who is not awestruck when contemplating green-clad mountains, valleys and plains? And are you not delighted by the sights and smells of forests, hills and dales? You need only visit areas man has greedily stripped to appreciate just how much earth’s verdure beautifies our home.
Like most of us, you probably trample over grass and shrubbery without giving thought to the fact that our very life depends on these green plants. How so?
Green Is for Growing
Pluck a green leaf from any tree or plant and examine it closely. Admire its symmetry and simple beauty. Observe its “plumbing” system of veins that gives the leaf firmness. It’s hard to believe that you hold in your hand a compact solar-powered factory, a laboratory of chemical wonders. But unlike ugly, smog-belching, noisy factories of today, that leaf carries out its work silently. And it enhances rather than pollutes its environment. How does it work?
First of all, it has been engineered to have a large surface area so it can collect energy from the sun. Usually, the side of the leaf facing the sun has a waxy feel. It is water-repellent and thus this retards water evaporation. To probe further, study the diagram on page 26. It gives you a ‘microscope’s-eye’ view of the leaf’s cross section.
You can see that a leaf is built like a layer cake. Under the waxy layer, there is the “palisade” layer of tiny, cylindrical cells. They stand upright like a line of marching soldiers. It is in these tiny cells that a chemical miracle takes place: photosynthesis.
Any plant lover knows that plants need light. Why? So that light passing through the shiny layer can hit these cylindrical cells. You see, within these tiny cells are yet smaller units called chloroplasts. They are filled with a remarkable pigment called chlorophyll. This pigment gives plants their green hue—and their life. Chlorophyll absorbs the energy from the sun. And before you can say “photosynthesis,” incredibly complex chemical reactions begin. Molecules of carbon dioxide (the gas you exhale from your lungs) and molecules of water present in the leaf are now split apart and recombined to form plant foods: carbohydrates, sugars and fats.
Ever since God gave Adam permission to eat “all vegetation bearing seed,” man has depended on these plant products for his very survival. (Genesis 1:29) Take, for example, the lowly grass. You may think there is little use for grass, other than for decorating lawns. Yet, perhaps the sugar with which you sweetened your morning cup of coffee is a grass product: sugarcane. Probably your breakfast cereal was also a grass, if it was made of wheat, barley, oats or rye. So is the rice you’ll be having with supper. No wonder the Encyclopedia Americana claims that “grass is the most important of all plants to man.” Botanist Lauren Brown further states: “Of the 15 major crops that stand between us and starvation, 10 are grasses.” And that’s just grass, not to mention apples and apricots, bananas and blueberries, carrots and cabbages, dates and dandelions, and so forth.
Let’s continue our tour of the leaf. The third section consists of a spongy layer of loosely packed cells. This allows room for the carbon dioxide to move through the leaf after it is “inhaled” by the bottom section.
Yes, take a look at the dull side of the leaf. You can’t see them, but there may be millions of perforations (called stomata) that act as adjustable intake and exhaust valves. The “intake valves” actually suck in carbon dioxide from the air for the photosynthesis reaction. When that reaction is complete, “exhaust valves” pump out an invaluable by-product—PURE OXYGEN!
Stop and think. Only about 20 percent of the air you breathe is oxygen. In just 24 hours you may inhale some 3,000 liters of oxygen. But you’ll only consume about one fourth as much, or 750 liters of the oxygen, for the body’s needs. Multiply that 750 liters (one day’s consumption) by the population of the world and you can see that a whole lot of oxygen is depleted by breathing alone. Some even estimate that 10 thousand tons of oxygen are consumed each second by breathing and other uses of oxygen, such as combustion to run your automobile. So what prevents us from using up the world’s oxygen supply and slowly suffocating?
It is the oxygen-producing photosynthesis that takes place in the leaves of plants on land and in water!
Plants—Past and Future
Man has not always fully appreciated his dependence on earth’s greenery. But in 1648 man started to penetrate the inner workings of the plant. In that year Belgian chemist van Helmont planted a five-pound (2 kg) willow shoot in a pot. The soil weighed in at 200 pounds (91 kg). Five years later he again weighed the willow: 169 pounds, 3 ounces (77 kg). The soil still weighed in at 200 pounds (91 kg)! Van Helmont now realized that plants do not grow by sucking in matter from the soil. So quite logically (but, alas, incorrectly!) he concluded that the growth of the tree was the result of its assimilating the water he had poured in the pot over the years!
Joseph Priestly came closer to the truth in 1772. This preacher and part-time chemist discovered that a burning candle consumes oxygen in a sealed container. A mouse placed in this oxygen-deprived container quickly died. But when a plant was placed in the container, the oxygen was replenished, and a mouse could live in the sealed environment.
Dutch physician Ingen-Housz further discovered that a plant must be exposed to light in order to produce this oxygen. He further noted that only the green portions of the plant (containing chlorophyll) responded in this way. By then man was on his way to understanding photosynthesis.
However, many discoveries and 200 years later, man still doesn’t fully understand how photosynthesis works. But, spurred on by scientific curiosity, concern for man’s future and visions of Nobel prizes, scientists by the hundreds steadily work to crack this intriguing mystery. Some hope to copy nature and manufacture all the food mankind could ever want. Others hope to tap an inexhaustible energy source. Already a number of different approaches are being studied.
It is ironic that such great interest in plants comes at a time when man is steadily wasting and destroying this great resource. In the United States, for example, reportedly 85 percent of the agricultural land is devoted to feeding not hungry people but fattened animals. This is in order to satiate the public’s appetite for red meats. (Per capita United States consumption of meat is 129 pounds (60 kg) a year, according to one writer.) Though nutritionists warn of health dangers in eating so much meat, the trend continues. Economists even fear that weaning people from a heavy meat diet could have dire economic consequences for farmers.
In other parts of the world, such as Brazil, forests are being stripped far faster than nature can replace them. In Germany air pollution, with its resultant acid rain, is threatening the life of its forests.
We can thus be glad that God will never permit this planet to become desolate and sterile. God “did not create it [the earth] simply for nothing.” (Isaiah 45:18) To the contrary, the prophet Joel assures us: “Do not be fearful, . . . for the pasture grounds of the wilderness will certainly grow green. For the tree will actually give its fruitage.”—Joel 2:22.
In the meantime we have many reasons to be thankful for earth’s green mantle. The lowly grass, the majestic oaks and sequoias, even the modest plant decorating your table, do more than just beautify. They feed and clothe us. They purify the air we breathe. They are vital to our survival.
So take a good look, an appreciative look, at earth’s beautiful covering. Be thankful that these green plants are there to serve us. Thank the Creator, “the One making the mountains to sprout green grass.”—Psalm 147:8.
[Blurb on page 27]
In many parts of the world forests are being stripped far faster than nature can replace them
[Picture on page 25]
Man has turned this . . .
. . . into this!
[Picture on page 26]
Photosynthesis takes place in this layer
Stomata take in carbon dioxide
Stomata expel oxygen