Expert: John Locke - 4/9/2007

Question
If we can assume that the plant is potted in soil, supplied with water and has 12 hours of light each day, can the plant survive in an air tight container?

Answer
Kristen, thank you for using AllExperts and I'd be happy to answer your question.

The answer is no. Plants require both oxygen and carbon dioxide to survive, in addition to sunlight and water. Now, as you are probably aware, plants are distinct from the animal kingdom particularly in their ability to manufacture their own nutrients via photosynthesis; this ability is called autotrophism (organisms that must consume their food are termed heterotrophs; humans--indeed, all animals--are heterotrophs).

The photosynthesis process takes carbon dioxide, water, and the energy from sunlight and produces carbohydrates, primarily cellulose, and oxygen as a byproduct. The stringy nature of celery is due to its being made mostly of cellulose, for example. Incidentally, this is also the reason that celery is a food favored by dieters--most of the carbohydrates that make up celery cannot be digested by humans, meaning that it contains few calories.

Plants also break down these carbohydrates to obtain energy--photosynthesis produces food, but a separate reaction is required to break down that food into a usable form. This process is identical to the one that occurs in animals and is called cellular respiration; it requires oxygen, water, and nutrients in the form of fats, proteins, and/or carbohydrates. Plants, of course, use mostly carbohydrates for their nutrition--that's what they make in photosynthesis! The net result of cellular respiration is a molecule termed ATP that can be used directly by cells for energy. Carbon dioxide is a byproduct.

Both of these processes require an atmosphere, however, and the amount of oxygen produced during photosynthesis is not equal to the amount of carbon dioxide produced during cellular respiration (far more oxygen is produced during photosynthesis; this fact explains how plants are primarily responsible for making the oxygen in the atmosphere).

The plant would likely survive for some time and undergo both processes, but eventually oxygen would replace almost all the carbon dioxide. The plant would be producing less and less cellulose by photosynthesis, but it would continue to experience cellular respiration at a fairly high rate. That is, cellular respiration would cause the breakdown of plant tissue faster than photosynthesis would add to it. Even though both processes would occur, the net result would be a wasting of the plant as it lost more and more of its energy stores. Eventually, the plant would be so starved that it would die, even with some carbon dioxide still in the container.