NOVA - Official Website | Illuminating Photosynthesis

Illuminating Photosynthesis
Photosynthesis in plants and a few bacteria is responsible for feeding nearly all life on Earth. It allows energy from the sun to be converted into a storable form, usually glucose, which plants use to grow and thrive. Photosynthesis also generates the oxygen that animals need to survive. But here we animals repay the favor. We exhale the carbon dioxide that plants need for photosynthesis. Here, take a closer look at the oxygen/carbon dioxide cycle and the process of photosynthesis.
This story reveals the secret of life,
or at least it reveals a small bit.
It shows how a plant uses light from the sun
and from this how we all benefit.
It shows you how plants create glucose.
It shows you the cycle of gases.
It asks you some relevant questions
that aren't asked in life science classes.
The Cycle
This kid and her plant use each other,
and this screen will show you just why.
When the kid and her plant interact,
all the molecules fly.
Well, a bonsai tree couldn't produce enough oxygen to keep someone alive, but an average-sized tree certainly could. In fact, an average-sized tree could produce enough oxygen to keep from two to four people alive.
Well, if you imagined that the "tree" in the question referred to a bonsai tree, then you made the right selectionâit certainly couldn't produce enough oxygen to keep a person alive. An average-sized tree, however, could produce enough oxygen to keep from two to four people alive.
This is really a trick question. "No" should be correctâa plant can't stay alive without a regular dose of lightâbut it isn't entirely correct. Yes, plants do need food to survive, and yes, they generally get this food through photosynthesis. However, experiments have shown that it is theoretically possible to keep a non-photosynthesizing plant alive, at least for a while.
John S. Boyer and his coworkers at the University of Delaware have kept the developing kernels of corn plants alive and growing in a low-light environment by feeding them sugar water. The sugar water, which was fed to the plants intravenously, sustained the growing kernels for five days. Without the sugar and light, the kernels would have died within a day.
This is really a trick question. "No" should be correctâa plant can't stay alive without a regular dose of lightâbut it isn't entirely correct. Yes, plants do need food to survive, and yes, they generally get this food through photosynthesis. However, experiments have shown that it is theoretically possible to keep a non-photosynthesizing plant alive, at least for a while.
John S. Boyer and his coworkers at the University of Delaware have kept the developing kernels of corn plants alive and growing in a low-light environment by feeding them sugar water. The sugar water, which was fed to the plants intravenously, sustained the growing kernels for five days. Without the sugar and light, the kernels would have died within a day.
The answer is actually "no, a plant could not grow without oxygen." Perhaps you're thinking that a plant needs to take in carbon dioxide in order to survive and that it expels oxygen as the waste product of photosynthesis. This is certainly true. But a plant doesn't only store the food it producesâit uses some to feed itself. And when a plant feeds on its own food, that food is broken down in the same way that it's broken down in an animal's body (including yours): with oxygen. The oxygen is needed to break down the carbohydrate molecules and release the energy stored in those molecules.
While a plant is photosynthesizing, it's producing more than enough oxygen to break down its own food. But if you were to take away the oxygen surrounding the plant as well as the light it needs for photosynthesis, the plant would in effect starve.
That's right. The plant would not grow. It is true that a plant needs to take in carbon dioxide in order to survive and that it expels oxygen as the waste product of photosynthesis. But a plant doesn't only store the food it producesâit uses some to feed itself. And when a plant feeds on its own food, that food is broken down in the same way that it's broken down in an animal's body (including yours): with oxygen. The oxygen is needed to break down the carbohydrate molecules and release the energy stored in those molecules.
While a plant is photosynthesizing, it's producing more than enough oxygen to break down its own food. But if you were to take away the oxygen surrounding the plant as well as the light it needs for photosynthesis, the plant would in effect starve.
This feature originally appeared on the site for the NOVA program Methuselah Tree.
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