This is my understatement of 2018: Plants are really, really good to us.
Sure, they make things pretty, but there’s sufficient evidence they improve health and well-being, too. We feel better when we’re surrounded by plants. Just walk around the Medical University of South Carolina and observe the investment in time and resources to beautify the campus. They know.
There’s the other obvious reason plants are good: They give us food. We can exist entirely off of plants, any vegetarian will tell you that. And there’s the whole oxygen thing, too. Plants absorb carbon dioxide to create glucose through the process of photosynthesis and release oxygen as a byproduct. Plants are making their own food. I don’t think we emphasize that enough. Give these organisms light and — boom — they feed themselves. Imagine coming home from the beach stuffed because you absorbed your daily allowance of sunlight.
Plants are the first trophic level on this planet. They are the organisms that convert solar energy into chemical energy, the molecules we call glucose, sucrose, starch and such. And then we eat them. Without these solar factories, we don’t exist. We’re here because of plants.
One of the things we do in the horticulture program at Trident Technical College is experiment. This is particularly fun in botany class where we test growth responses. For instance, plants react to environmental stimuli such as gravity and sunlight. These are called trophic responses and almost seem like active intelligence at work.
When put in a dark closet, plants will bend toward a single light source, a phenomenon called phototropism. Plants figured out that more light equals more photosynthesis equals more food equals more growth. Light inhibits cell elongation on the side of the stem it illuminates. However, the shady side of the stem continues growing at a normal rate. The difference between the two growth rates causes it to bend toward the light.
And quality of light matters, too. When we expose plants to green light, their growth habit becomes thin and leggy. They’re stretching. This growth response allows them to grow taller faster. This is because green light is a poor spectrum of sunlight for photosynthesis. It’s why plants are green: they’re reflecting the green spectrum. And their growth response to green light is perfect. Plants growing in a forest are getting dappled sunlight at best, and most of it is the poor part of the light spectrum. They’re trying to reach the top where good sunlight is.
We’ve put them under shade cloth and seen the same response. They become so structurally weak and begin to lean and, as a result, find sunlight outside the shaded test area. Genius.
It’s usually, however, a race to the top. Take vines, for instance. They put all their resources into growing fast. Kudzu can grow as much as a foot per day. If you’re patient, you can see it happen. However, this fast growth is at the expense of structure, so they wind around tree trunks to reach the top. This winding response is called thigmotropism. Much like phototropism, cell growth is suppressed where the stem contacts a physical object but the cells on the other side of the stem continue elongating. Thus the winding.
And once again, genius.
It’s the red and blue spectrum of light that matters most to photosynthesis. Blue facilitates foliar growth and red initiates flowering. Of course, we’re testing this in a closet with sunflowers to find out if it’s true.
Your houseplants may be suffering from low quality light. Of course, there’s plenty of sunlight for us to read a book, but it might be insufficient for photosynthesis. One solution is to grow shade-tolerant houseplants such as philodendron. These are plants that evolved to take advantage of low or poor quality light. Increasing light quality is difficult unless you move them closer to the window or add grow lights.
So don’t take your role as a gardener lightly. Every plant we nurture is helping more than just us. And I think they know it. They give thanks with sweet berries.
Because plants are really, really good to us.